Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 2463 insertions, 0 deletions

diff --git a/drivers/atm/ambassador.c b/drivers/atm/ambassador.c
new file mode 100644
index 000000000000..c46d9520c5a7
--- /dev/null
+++ b/drivers/atm/ambassador.c
@@ -0,0 +1,2463 @@
+/*
+  Madge Ambassador ATM Adapter driver.
+  Copyright (C) 1995-1999  Madge Networks Ltd.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+  The GNU GPL is contained in /usr/doc/copyright/GPL on a Debian
+  system and in the file COPYING in the Linux kernel source.
+*/
+
+/* * dedicated to the memory of Graham Gordon 1971-1998 * */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/pci.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/atmdev.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+
+#include <asm/atomic.h>
+#include <asm/io.h>
+#include <asm/byteorder.h>
+
+#include "ambassador.h"
+
+#define maintainer_string "Giuliano Procida at Madge Networks <gprocida@madge.com>"
+#define description_string "Madge ATM Ambassador driver"
+#define version_string "1.2.4"
+
+static inline void __init show_version (void) {
+  printk ("%s version %s\n", description_string, version_string);
+}
+
+/*
+  
+  Theory of Operation
+  
+  I Hardware, detection, initialisation and shutdown.
+  
+  1. Supported Hardware
+  
+  This driver is for the PCI ATMizer-based Ambassador card (except
+  very early versions). It is not suitable for the similar EISA "TR7"
+  card. Commercially, both cards are known as Collage Server ATM
+  adapters.
+  
+  The loader supports image transfer to the card, image start and few
+  other miscellaneous commands.
+  
+  Only AAL5 is supported with vpi = 0 and vci in the range 0 to 1023.
+  
+  The cards are big-endian.
+  
+  2. Detection
+  
+  Standard PCI stuff, the early cards are detected and rejected.
+  
+  3. Initialisation
+  
+  The cards are reset and the self-test results are checked. The
+  microcode image is then transferred and started. This waits for a
+  pointer to a descriptor containing details of the host-based queues
+  and buffers and various parameters etc. Once they are processed
+  normal operations may begin. The BIA is read using a microcode
+  command.
+  
+  4. Shutdown
+  
+  This may be accomplished either by a card reset or via the microcode
+  shutdown command. Further investigation required.
+  
+  5. Persistent state
+  
+  The card reset does not affect PCI configuration (good) or the
+  contents of several other "shared run-time registers" (bad) which
+  include doorbell and interrupt control as well as EEPROM and PCI
+  control. The driver must be careful when modifying these registers
+  not to touch bits it does not use and to undo any changes at exit.
+  
+  II Driver software
+  
+  0. Generalities
+  
+  The adapter is quite intelligent (fast) and has a simple interface
+  (few features). VPI is always zero, 1024 VCIs are supported. There
+  is limited cell rate support. UBR channels can be capped and ABR
+  (explicit rate, but not EFCI) is supported. There is no CBR or VBR
+  support.
+  
+  1. Driver <-> Adapter Communication
+  
+  Apart from the basic loader commands, the driver communicates
+  through three entities: the command queue (CQ), the transmit queue
+  pair (TXQ) and the receive queue pairs (RXQ). These three entities
+  are set up by the host and passed to the microcode just after it has
+  been started.
+  
+  All queues are host-based circular queues. They are contiguous and
+  (due to hardware limitations) have some restrictions as to their
+  locations in (bus) memory. They are of the "full means the same as
+  empty so don't do that" variety since the adapter uses pointers
+  internally.
+  
+  The queue pairs work as follows: one queue is for supply to the
+  adapter, items in it are pending and are owned by the adapter; the
+  other is the queue for return from the adapter, items in it have
+  been dealt with by the adapter. The host adds items to the supply
+  (TX descriptors and free RX buffer descriptors) and removes items
+  from the return (TX and RX completions). The adapter deals with out
+  of order completions.
+  
+  Interrupts (card to host) and the doorbell (host to card) are used
+  for signalling.
+  
+  1. CQ
+  
+  This is to communicate "open VC", "close VC", "get stats" etc. to
+  the adapter. At most one command is retired every millisecond by the
+  card. There is no out of order completion or notification. The
+  driver needs to check the return code of the command, waiting as
+  appropriate.
+  
+  2. TXQ
+  
+  TX supply items are of variable length (scatter gather support) and
+  so the queue items are (more or less) pointers to the real thing.
+  Each TX supply item contains a unique, host-supplied handle (the skb
+  bus address seems most sensible as this works for Alphas as well,
+  there is no need to do any endian conversions on the handles).
+  
+  TX return items consist of just the handles above.
+  
+  3. RXQ (up to 4 of these with different lengths and buffer sizes)
+  
+  RX supply items consist of a unique, host-supplied handle (the skb
+  bus address again) and a pointer to the buffer data area.
+  
+  RX return items consist of the handle above, the VC, length and a
+  status word. This just screams "oh so easy" doesn't it?
+
+  Note on RX pool sizes:
+   
+  Each pool should have enough buffers to handle a back-to-back stream
+  of minimum sized frames on a single VC. For example:
+  
+    frame spacing = 3us (about right)
+    
+    delay = IRQ lat + RX handling + RX buffer replenish = 20 (us)  (a guess)
+    
+    min number of buffers for one VC = 1 + delay/spacing (buffers)
+
+    delay/spacing = latency = (20+2)/3 = 7 (buffers)  (rounding up)
+    
+  The 20us delay assumes that there is no need to sleep; if we need to
+  sleep to get buffers we are going to drop frames anyway.
+  
+  In fact, each pool should have enough buffers to support the
+  simultaneous reassembly of a separate frame on each VC and cope with
+  the case in which frames complete in round robin cell fashion on
+  each VC.
+  
+  Only one frame can complete at each cell arrival, so if "n" VCs are
+  open, the worst case is to have them all complete frames together
+  followed by all starting new frames together.
+  
+    desired number of buffers = n + delay/spacing
+    
+  These are the extreme requirements, however, they are "n+k" for some
+  "k" so we have only the constant to choose. This is the argument
+  rx_lats which current defaults to 7.
+  
+  Actually, "n ? n+k : 0" is better and this is what is implemented,
+  subject to the limit given by the pool size.
+  
+  4. Driver locking
+  
+  Simple spinlocks are used around the TX and RX queue mechanisms.
+  Anyone with a faster, working method is welcome to implement it.
+  
+  The adapter command queue is protected with a spinlock. We always
+  wait for commands to complete.
+  
+  A more complex form of locking is used around parts of the VC open
+  and close functions. There are three reasons for a lock: 1. we need
+  to do atomic rate reservation and release (not used yet), 2. Opening
+  sometimes involves two adapter commands which must not be separated
+  by another command on the same VC, 3. the changes to RX pool size
+  must be atomic. The lock needs to work over context switches, so we
+  use a semaphore.
+  
+  III Hardware Features and Microcode Bugs
+  
+  1. Byte Ordering
+  
+  *%^"$&%^$*&^"$(%^$#&^%$(&#%$*(&^#%!"!"!*!
+  
+  2. Memory access
+  
+  All structures that are not accessed using DMA must be 4-byte
+  aligned (not a problem) and must not cross 4MB boundaries.
+  
+  There is a DMA memory hole at E0000000-E00000FF (groan).
+  
+  TX fragments (DMA read) must not cross 4MB boundaries (would be 16MB
+  but for a hardware bug).
+  
+  RX buffers (DMA write) must not cross 16MB boundaries and must
+  include spare trailing bytes up to the next 4-byte boundary; they
+  will be written with rubbish.
+  
+  The PLX likes to prefetch; if reading up to 4 u32 past the end of
+  each TX fragment is not a problem, then TX can be made to go a
+  little faster by passing a flag at init that disables a prefetch
+  workaround. We do not pass this flag. (new microcode only)
+  
+  Now we:
+  . Note that alloc_skb rounds up size to a 16byte boundary.  
+  . Ensure all areas do not traverse 4MB boundaries.
+  . Ensure all areas do not start at a E00000xx bus address.
+  (I cannot be certain, but this may always hold with Linux)
+  . Make all failures cause a loud message.
+  . Discard non-conforming SKBs (causes TX failure or RX fill delay).
+  . Discard non-conforming TX fragment descriptors (the TX fails).
+  In the future we could:
+  . Allow RX areas that traverse 4MB (but not 16MB) boundaries.
+  . Segment TX areas into some/more fragments, when necessary.
+  . Relax checks for non-DMA items (ignore hole).
+  . Give scatter-gather (iovec) requirements using ???. (?)
+  
+  3. VC close is broken (only for new microcode)
+  
+  The VC close adapter microcode command fails to do anything if any
+  frames have been received on the VC but none have been transmitted.
+  Frames continue to be reassembled and passed (with IRQ) to the
+  driver.
+  
+  IV To Do List
+  
+  . Fix bugs!
+  
+  . Timer code may be broken.
+  
+  . Deal with buggy VC close (somehow) in microcode 12.
+  
+  . Handle interrupted and/or non-blocking writes - is this a job for
+    the protocol layer?
+  
+  . Add code to break up TX fragments when they span 4MB boundaries.
+  
+  . Add SUNI phy layer (need to know where SUNI lives on card).
+  
+  . Implement a tx_alloc fn to (a) satisfy TX alignment etc. and (b)
+    leave extra headroom space for Ambassador TX descriptors.
+  
+  . Understand these elements of struct atm_vcc: recvq (proto?),
+    sleep, callback, listenq, backlog_quota, reply and user_back.
+  
+  . Adjust TX/RX skb allocation to favour IP with LANE/CLIP (configurable).
+  
+  . Impose a TX-pending limit (2?) on each VC, help avoid TX q overflow.
+  
+  . Decide whether RX buffer recycling is or can be made completely safe;
+    turn it back on. It looks like Werner is going to axe this.
+  
+  . Implement QoS changes on open VCs (involves extracting parts of VC open
+    and close into separate functions and using them to make changes).
+  
+  . Hack on command queue so that someone can issue multiple commands and wait
+    on the last one (OR only "no-op" or "wait" commands are waited for).
+  
+  . Eliminate need for while-schedule around do_command.
+  
+*/
+
+/********** microcode **********/
+
+#ifdef AMB_NEW_MICROCODE
+#define UCODE(x) UCODE2(atmsar12.x)
+#else
+#define UCODE(x) UCODE2(atmsar11.x)
+#endif
+#define UCODE2(x) #x
+
+static u32 __devinitdata ucode_start =
+#include UCODE(start)
+;
+
+static region __devinitdata ucode_regions[] = {
+#include UCODE(regions)
+  { 0, 0 }
+};
+
+static u32 __devinitdata ucode_data[] = {
+#include UCODE(data)
+  0xdeadbeef
+};
+
+static void do_housekeeping (unsigned long arg);
+/********** globals **********/
+
+static unsigned short debug = 0;
+static unsigned int cmds = 8;
+static unsigned int txs = 32;
+static unsigned int rxs[NUM_RX_POOLS] = { 64, 64, 64, 64 };
+static unsigned int rxs_bs[NUM_RX_POOLS] = { 4080, 12240, 36720, 65535 };
+static unsigned int rx_lats = 7;
+static unsigned char pci_lat = 0;
+
+static const unsigned long onegigmask = -1 << 30;
+
+/********** access to adapter **********/
+
+static inline void wr_plain (const amb_dev * dev, size_t addr, u32 data) {
+  PRINTD (DBG_FLOW|DBG_REGS, "wr: %08zx <- %08x", addr, data);
+#ifdef AMB_MMIO
+  dev->membase[addr / sizeof(u32)] = data;
+#else
+  outl (data, dev->iobase + addr);
+#endif
+}
+
+static inline u32 rd_plain (const amb_dev * dev, size_t addr) {
+#ifdef AMB_MMIO
+  u32 data = dev->membase[addr / sizeof(u32)];
+#else
+  u32 data = inl (dev->iobase + addr);
+#endif
+  PRINTD (DBG_FLOW|DBG_REGS, "rd: %08zx -> %08x", addr, data);
+  return data;
+}
+
+static inline void wr_mem (const amb_dev * dev, size_t addr, u32 data) {
+  __be32 be = cpu_to_be32 (data);
+  PRINTD (DBG_FLOW|DBG_REGS, "wr: %08zx <- %08x b[%08x]", addr, data, be);
+#ifdef AMB_MMIO
+  dev->membase[addr / sizeof(u32)] = be;
+#else
+  outl (be, dev->iobase + addr);
+#endif
+}
+
+static inline u32 rd_mem (const amb_dev * dev, size_t addr) {
+#ifdef AMB_MMIO
+  __be32 be = dev->membase[addr / sizeof(u32)];
+#else
+  __be32 be = inl (dev->iobase + addr);
+#endif
+  u32 data = be32_to_cpu (be);
+  PRINTD (DBG_FLOW|DBG_REGS, "rd: %08zx -> %08x b[%08x]", addr, data, be);
+  return data;
+}
+
+/********** dump routines **********/
+
+static inline void dump_registers (const amb_dev * dev) {
+#ifdef DEBUG_AMBASSADOR
+  if (debug & DBG_REGS) {
+    size_t i;
+    PRINTD (DBG_REGS, "reading PLX control: ");
+    for (i = 0x00; i < 0x30; i += sizeof(u32))
+      rd_mem (dev, i);
+    PRINTD (DBG_REGS, "reading mailboxes: ");
+    for (i = 0x40; i < 0x60; i += sizeof(u32))
+      rd_mem (dev, i);
+    PRINTD (DBG_REGS, "reading doorb irqev irqen reset:");
+    for (i = 0x60; i < 0x70; i += sizeof(u32))
+      rd_mem (dev, i);
+  }
+#else
+  (void) dev;
+#endif
+  return;
+}
+
+static inline void dump_loader_block (volatile loader_block * lb) {
+#ifdef DEBUG_AMBASSADOR
+  unsigned int i;
+  PRINTDB (DBG_LOAD, "lb @ %p; res: %d, cmd: %d, pay:",
+           lb, be32_to_cpu (lb->result), be32_to_cpu (lb->command));
+  for (i = 0; i < MAX_COMMAND_DATA; ++i)
+    PRINTDM (DBG_LOAD, " %08x", be32_to_cpu (lb->payload.data[i]));
+  PRINTDE (DBG_LOAD, ", vld: %08x", be32_to_cpu (lb->valid));
+#else
+  (void) lb;
+#endif
+  return;
+}
+
+static inline void dump_command (command * cmd) {
+#ifdef DEBUG_AMBASSADOR
+  unsigned int i;
+  PRINTDB (DBG_CMD, "cmd @ %p, req: %08x, pars:",
+           cmd, /*be32_to_cpu*/ (cmd->request));
+  for (i = 0; i < 3; ++i)
+    PRINTDM (DBG_CMD, " %08x", /*be32_to_cpu*/ (cmd->args.par[i]));
+  PRINTDE (DBG_CMD, "");
+#else
+  (void) cmd;
+#endif
+  return;
+}
+
+static inline void dump_skb (char * prefix, unsigned int vc, struct sk_buff * skb) {
+#ifdef DEBUG_AMBASSADOR
+  unsigned int i;
+  unsigned char * data = skb->data;
+  PRINTDB (DBG_DATA, "%s(%u) ", prefix, vc);
+  for (i=0; i<skb->len && i < 256;i++)
+    PRINTDM (DBG_DATA, "%02x ", data[i]);
+  PRINTDE (DBG_DATA,"");
+#else
+  (void) prefix;
+  (void) vc;
+  (void) skb;
+#endif
+  return;
+}
+
+/********** check memory areas for use by Ambassador **********/
+
+/* see limitations under Hardware Features */
+
+static inline int check_area (void * start, size_t length) {
+  // assumes length > 0
+  const u32 fourmegmask = -1 << 22;
+  const u32 twofivesixmask = -1 << 8;
+  const u32 starthole = 0xE0000000;
+  u32 startaddress = virt_to_bus (start);
+  u32 lastaddress = startaddress+length-1;
+  if ((startaddress ^ lastaddress) & fourmegmask ||
+      (startaddress & twofivesixmask) == starthole) {
+    PRINTK (KERN_ERR, "check_area failure: [%x,%x] - mail maintainer!",
+            startaddress, lastaddress);
+    return -1;
+  } else {
+    return 0;
+  }
+}
+
+/********** free an skb (as per ATM device driver documentation) **********/
+
+static inline void amb_kfree_skb (struct sk_buff * skb) {
+  if (ATM_SKB(skb)->vcc->pop) {
+    ATM_SKB(skb)->vcc->pop (ATM_SKB(skb)->vcc, skb);
+  } else {
+    dev_kfree_skb_any (skb);
+  }
+}
+
+/********** TX completion **********/
+
+static inline void tx_complete (amb_dev * dev, tx_out * tx) {
+  tx_simple * tx_descr = bus_to_virt (tx->handle);
+  struct sk_buff * skb = tx_descr->skb;
+  
+  PRINTD (DBG_FLOW|DBG_TX, "tx_complete %p %p", dev, tx);
+  
+  // VC layer stats
+  atomic_inc(&ATM_SKB(skb)->vcc->stats->tx);
+  
+  // free the descriptor
+  kfree (tx_descr);
+  
+  // free the skb
+  amb_kfree_skb (skb);
+  
+  dev->stats.tx_ok++;
+  return;
+}
+
+/********** RX completion **********/
+
+static void rx_complete (amb_dev * dev, rx_out * rx) {
+  struct sk_buff * skb = bus_to_virt (rx->handle);
+  u16 vc = be16_to_cpu (rx->vc);
+  // unused: u16 lec_id = be16_to_cpu (rx->lec_id);
+  u16 status = be16_to_cpu (rx->status);
+  u16 rx_len = be16_to_cpu (rx->length);
+  
+  PRINTD (DBG_FLOW|DBG_RX, "rx_complete %p %p (len=%hu)", dev, rx, rx_len);
+  
+  // XXX move this in and add to VC stats ???
+  if (!status) {
+    struct atm_vcc * atm_vcc = dev->rxer[vc];
+    dev->stats.rx.ok++;
+    
+    if (atm_vcc) {
+      
+      if (rx_len <= atm_vcc->qos.rxtp.max_sdu) {
+        
+        if (atm_charge (atm_vcc, skb->truesize)) {
+          
+          // prepare socket buffer
+          ATM_SKB(skb)->vcc = atm_vcc;
+          skb_put (skb, rx_len);
+          
+          dump_skb ("<<<", vc, skb);
+          
+          // VC layer stats
+          atomic_inc(&atm_vcc->stats->rx);
+          do_gettimeofday(&skb->stamp);
+          // end of our responsability
+          atm_vcc->push (atm_vcc, skb);
+          return;
+          
+        } else {
+          // someone fix this (message), please!
+          PRINTD (DBG_INFO|DBG_RX, "dropped thanks to atm_charge (vc %hu, truesize %u)", vc, skb->truesize);
+          // drop stats incremented in atm_charge
+        }
+        
+      } else {
+        PRINTK (KERN_INFO, "dropped over-size frame");
+        // should we count this?
+        atomic_inc(&atm_vcc->stats->rx_drop);
+      }
+      
+    } else {
+      PRINTD (DBG_WARN|DBG_RX, "got frame but RX closed for channel %hu", vc);
+      // this is an adapter bug, only in new version of microcode
+    }
+    
+  } else {
+    dev->stats.rx.error++;
+    if (status & CRC_ERR)
+      dev->stats.rx.badcrc++;
+    if (status & LEN_ERR)
+      dev->stats.rx.toolong++;
+    if (status & ABORT_ERR)
+      dev->stats.rx.aborted++;
+    if (status & UNUSED_ERR)
+      dev->stats.rx.unused++;
+  }
+  
+  dev_kfree_skb_any (skb);
+  return;
+}
+
+/*
+  
+  Note on queue handling.
+  
+  Here "give" and "take" refer to queue entries and a queue (pair)
+  rather than frames to or from the host or adapter. Empty frame
+  buffers are given to the RX queue pair and returned unused or
+  containing RX frames. TX frames (well, pointers to TX fragment
+  lists) are given to the TX queue pair, completions are returned.
+  
+*/
+
+/********** command queue **********/
+
+// I really don't like this, but it's the best I can do at the moment
+
+// also, the callers are responsible for byte order as the microcode
+// sometimes does 16-bit accesses (yuk yuk yuk)
+
+static int command_do (amb_dev * dev, command * cmd) {
+  amb_cq * cq = &dev->cq;
+  volatile amb_cq_ptrs * ptrs = &cq->ptrs;
+  command * my_slot;
+  
+  PRINTD (DBG_FLOW|DBG_CMD, "command_do %p", dev);
+  
+  if (test_bit (dead, &dev->flags))
+    return 0;
+  
+  spin_lock (&cq->lock);
+  
+  // if not full...
+  if (cq->pending < cq->maximum) {
+    // remember my slot for later
+    my_slot = ptrs->in;
+    PRINTD (DBG_CMD, "command in slot %p", my_slot);
+    
+    dump_command (cmd);
+    
+    // copy command in
+    *ptrs->in = *cmd;
+    cq->pending++;
+    ptrs->in = NEXTQ (ptrs->in, ptrs->start, ptrs->limit);
+    
+    // mail the command
+    wr_mem (dev, offsetof(amb_mem, mb.adapter.cmd_address), virt_to_bus (ptrs->in));
+    
+    if (cq->pending > cq->high)
+      cq->high = cq->pending;
+    spin_unlock (&cq->lock);
+    
+    // these comments were in a while-loop before, msleep removes the loop
+    // go to sleep
+    // PRINTD (DBG_CMD, "wait: sleeping %lu for command", timeout);
+    msleep(cq->pending);
+    
+    // wait for my slot to be reached (all waiters are here or above, until...)
+    while (ptrs->out != my_slot) {
+      PRINTD (DBG_CMD, "wait: command slot (now at %p)", ptrs->out);
+      set_current_state(TASK_UNINTERRUPTIBLE);
+      schedule();
+    }
+    
+    // wait on my slot (... one gets to its slot, and... )
+    while (ptrs->out->request != cpu_to_be32 (SRB_COMPLETE)) {
+      PRINTD (DBG_CMD, "wait: command slot completion");
+      set_current_state(TASK_UNINTERRUPTIBLE);
+      schedule();
+    }
+    
+    PRINTD (DBG_CMD, "command complete");
+    // update queue (... moves the queue along to the next slot)
+    spin_lock (&cq->lock);
+    cq->pending--;
+    // copy command out
+    *cmd = *ptrs->out;
+    ptrs->out = NEXTQ (ptrs->out, ptrs->start, ptrs->limit);
+    spin_unlock (&cq->lock);
+    
+    return 0;
+  } else {
+    cq->filled++;
+    spin_unlock (&cq->lock);
+    return -EAGAIN;
+  }
+  
+}
+
+/********** TX queue pair **********/
+
+static inline int tx_give (amb_dev * dev, tx_in * tx) {
+  amb_txq * txq = &dev->txq;
+  unsigned long flags;
+  
+  PRINTD (DBG_FLOW|DBG_TX, "tx_give %p", dev);
+
+  if (test_bit (dead, &dev->flags))
+    return 0;
+  
+  spin_lock_irqsave (&txq->lock, flags);
+  
+  if (txq->pending < txq->maximum) {
+    PRINTD (DBG_TX, "TX in slot %p", txq->in.ptr);
+
+    *txq->in.ptr = *tx;
+    txq->pending++;
+    txq->in.ptr = NEXTQ (txq->in.ptr, txq->in.start, txq->in.limit);
+    // hand over the TX and ring the bell
+    wr_mem (dev, offsetof(amb_mem, mb.adapter.tx_address), virt_to_bus (txq->in.ptr));
+    wr_mem (dev, offsetof(amb_mem, doorbell), TX_FRAME);
+    
+    if (txq->pending > txq->high)
+      txq->high = txq->pending;
+    spin_unlock_irqrestore (&txq->lock, flags);
+    return 0;
+  } else {
+    txq->filled++;
+    spin_unlock_irqrestore (&txq->lock, flags);
+    return -EAGAIN;
+  }
+}
+
+static inline int tx_take (amb_dev * dev) {
+  amb_txq * txq = &dev->txq;
+  unsigned long flags;
+  
+  PRINTD (DBG_FLOW|DBG_TX, "tx_take %p", dev);
+  
+  spin_lock_irqsave (&txq->lock, flags);
+  
+  if (txq->pending && txq->out.ptr->handle) {
+    // deal with TX completion
+    tx_complete (dev, txq->out.ptr);
+    // mark unused again
+    txq->out.ptr->handle = 0;
+    // remove item
+    txq->pending--;
+    txq->out.ptr = NEXTQ (txq->out.ptr, txq->out.start, txq->out.limit);
+    
+    spin_unlock_irqrestore (&txq->lock, flags);
+    return 0;
+  } else {
+    
+    spin_unlock_irqrestore (&txq->lock, flags);
+    return -1;
+  }
+}
+
+/********** RX queue pairs **********/
+
+static inline int rx_give (amb_dev * dev, rx_in * rx, unsigned char pool) {
+  amb_rxq * rxq = &dev->rxq[pool];
+  unsigned long flags;
+  
+  PRINTD (DBG_FLOW|DBG_RX, "rx_give %p[%hu]", dev, pool);
+  
+  spin_lock_irqsave (&rxq->lock, flags);
+  
+  if (rxq->pending < rxq->maximum) {
+    PRINTD (DBG_RX, "RX in slot %p", rxq->in.ptr);
+
+    *rxq->in.ptr = *rx;
+    rxq->pending++;
+    rxq->in.ptr = NEXTQ (rxq->in.ptr, rxq->in.start, rxq->in.limit);
+    // hand over the RX buffer
+    wr_mem (dev, offsetof(amb_mem, mb.adapter.rx_address[pool]), virt_to_bus (rxq->in.ptr));
+    
+    spin_unlock_irqrestore (&rxq->lock, flags);
+    return 0;
+  } else {
+    spin_unlock_irqrestore (&rxq->lock, flags);
+    return -1;
+  }
+}
+
+static inline int rx_take (amb_dev * dev, unsigned char pool) {
+  amb_rxq * rxq = &dev->rxq[pool];
+  unsigned long flags;
+  
+  PRINTD (DBG_FLOW|DBG_RX, "rx_take %p[%hu]", dev, pool);
+  
+  spin_lock_irqsave (&rxq->lock, flags);
+  
+  if (rxq->pending && (rxq->out.ptr->status || rxq->out.ptr->length)) {
+    // deal with RX completion
+    rx_complete (dev, rxq->out.ptr);
+    // mark unused again
+    rxq->out.ptr->status = 0;
+    rxq->out.ptr->length = 0;
+    // remove item
+    rxq->pending--;
+    rxq->out.ptr = NEXTQ (rxq->out.ptr, rxq->out.start, rxq->out.limit);
+    
+    if (rxq->pending < rxq->low)
+      rxq->low = rxq->pending;
+    spin_unlock_irqrestore (&rxq->lock, flags);
+    return 0;
+  } else {
+    if (!rxq->pending && rxq->buffers_wanted)
+      rxq->emptied++;
+    spin_unlock_irqrestore (&rxq->lock, flags);
+    return -1;
+  }
+}
+
+/********** RX Pool handling **********/
+
+/* pre: buffers_wanted = 0, post: pending = 0 */
+static inline void drain_rx_pool (amb_dev * dev, unsigned char pool) {
+  amb_rxq * rxq = &dev->rxq[pool];
+  
+  PRINTD (DBG_FLOW|DBG_POOL, "drain_rx_pool %p %hu", dev, pool);
+  
+  if (test_bit (dead, &dev->flags))
+    return;
+  
+  /* we are not quite like the fill pool routines as we cannot just
+     remove one buffer, we have to remove all of them, but we might as
+     well pretend... */
+  if (rxq->pending > rxq->buffers_wanted) {
+    command cmd;
+    cmd.request = cpu_to_be32 (SRB_FLUSH_BUFFER_Q);
+    cmd.args.flush.flags = cpu_to_be32 (pool << SRB_POOL_SHIFT);
+    while (command_do (dev, &cmd))
+      schedule();
+    /* the pool may also be emptied via the interrupt handler */
+    while (rxq->pending > rxq->buffers_wanted)
+      if (rx_take (dev, pool))
+        schedule();
+  }
+  
+  return;
+}
+
+static void drain_rx_pools (amb_dev * dev) {
+  unsigned char pool;
+  
+  PRINTD (DBG_FLOW|DBG_POOL, "drain_rx_pools %p", dev);
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+    drain_rx_pool (dev, pool);
+}
+
+static inline void fill_rx_pool (amb_dev * dev, unsigned char pool, int priority) {
+  rx_in rx;
+  amb_rxq * rxq;
+  
+  PRINTD (DBG_FLOW|DBG_POOL, "fill_rx_pool %p %hu %x", dev, pool, priority);
+  
+  if (test_bit (dead, &dev->flags))
+    return;
+  
+  rxq = &dev->rxq[pool];
+  while (rxq->pending < rxq->maximum && rxq->pending < rxq->buffers_wanted) {
+    
+    struct sk_buff * skb = alloc_skb (rxq->buffer_size, priority);
+    if (!skb) {
+      PRINTD (DBG_SKB|DBG_POOL, "failed to allocate skb for RX pool %hu", pool);
+      return;
+    }
+    if (check_area (skb->data, skb->truesize)) {
+      dev_kfree_skb_any (skb);
+      return;
+    }
+    // cast needed as there is no %? for pointer differences
+    PRINTD (DBG_SKB, "allocated skb at %p, head %p, area %li",
+            skb, skb->head, (long) (skb->end - skb->head));
+    rx.handle = virt_to_bus (skb);
+    rx.host_address = cpu_to_be32 (virt_to_bus (skb->data));
+    if (rx_give (dev, &rx, pool))
+      dev_kfree_skb_any (skb);
+    
+  }
+  
+  return;
+}
+
+// top up all RX pools (can also be called as a bottom half)
+static void fill_rx_pools (amb_dev * dev) {
+  unsigned char pool;
+  
+  PRINTD (DBG_FLOW|DBG_POOL, "fill_rx_pools %p", dev);
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+    fill_rx_pool (dev, pool, GFP_ATOMIC);
+  
+  return;
+}
+
+/********** enable host interrupts **********/
+
+static inline void interrupts_on (amb_dev * dev) {
+  wr_plain (dev, offsetof(amb_mem, interrupt_control),
+            rd_plain (dev, offsetof(amb_mem, interrupt_control))
+            | AMB_INTERRUPT_BITS);
+}
+
+/********** disable host interrupts **********/
+
+static inline void interrupts_off (amb_dev * dev) {
+  wr_plain (dev, offsetof(amb_mem, interrupt_control),
+            rd_plain (dev, offsetof(amb_mem, interrupt_control))
+            &~ AMB_INTERRUPT_BITS);
+}
+
+/********** interrupt handling **********/
+
+static irqreturn_t interrupt_handler(int irq, void *dev_id,
+                                        struct pt_regs *pt_regs) {
+  amb_dev * dev = (amb_dev *) dev_id;
+  (void) pt_regs;
+  
+  PRINTD (DBG_IRQ|DBG_FLOW, "interrupt_handler: %p", dev_id);
+  
+  if (!dev_id) {
+    PRINTD (DBG_IRQ|DBG_ERR, "irq with NULL dev_id: %d", irq);
+    return IRQ_NONE;
+  }
+  
+  {
+    u32 interrupt = rd_plain (dev, offsetof(amb_mem, interrupt));
+  
+    // for us or someone else sharing the same interrupt
+    if (!interrupt) {
+      PRINTD (DBG_IRQ, "irq not for me: %d", irq);
+      return IRQ_NONE;
+    }
+    
+    // definitely for us
+    PRINTD (DBG_IRQ, "FYI: interrupt was %08x", interrupt);
+    wr_plain (dev, offsetof(amb_mem, interrupt), -1);
+  }
+  
+  {
+    unsigned int irq_work = 0;
+    unsigned char pool;
+    for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+      while (!rx_take (dev, pool))
+        ++irq_work;
+    while (!tx_take (dev))
+      ++irq_work;
+  
+    if (irq_work) {
+#ifdef FILL_RX_POOLS_IN_BH
+      schedule_work (&dev->bh);
+#else
+      fill_rx_pools (dev);
+#endif
+
+      PRINTD (DBG_IRQ, "work done: %u", irq_work);
+    } else {
+      PRINTD (DBG_IRQ|DBG_WARN, "no work done");
+    }
+  }
+  
+  PRINTD (DBG_IRQ|DBG_FLOW, "interrupt_handler done: %p", dev_id);
+  return IRQ_HANDLED;
+}
+
+/********** make rate (not quite as much fun as Horizon) **********/
+
+static unsigned int make_rate (unsigned int rate, rounding r,
+                               u16 * bits, unsigned int * actual) {
+  unsigned char exp = -1; // hush gcc
+  unsigned int man = -1;  // hush gcc
+  
+  PRINTD (DBG_FLOW|DBG_QOS, "make_rate %u", rate);
+  
+  // rates in cells per second, ITU format (nasty 16-bit floating-point)
+  // given 5-bit e and 9-bit m:
+  // rate = EITHER (1+m/2^9)*2^e    OR 0
+  // bits = EITHER 1<<14 | e<<9 | m OR 0
+  // (bit 15 is "reserved", bit 14 "non-zero")
+  // smallest rate is 0 (special representation)
+  // largest rate is (1+511/512)*2^31 = 4290772992 (< 2^32-1)
+  // smallest non-zero rate is (1+0/512)*2^0 = 1 (> 0)
+  // simple algorithm:
+  // find position of top bit, this gives e
+  // remove top bit and shift (rounding if feeling clever) by 9-e
+  
+  // ucode bug: please don't set bit 14! so 0 rate not representable
+  
+  if (rate > 0xffc00000U) {
+    // larger than largest representable rate
+    
+    if (r == round_up) {
+        return -EINVAL;
+    } else {
+      exp = 31;
+      man = 511;
+    }
+    
+  } else if (rate) {
+    // representable rate
+    
+    exp = 31;
+    man = rate;
+    
+    // invariant: rate = man*2^(exp-31)
+    while (!(man & (1<<31))) {
+      exp = exp - 1;
+      man = man<<1;
+    }
+    
+    // man has top bit set
+    // rate = (2^31+(man-2^31))*2^(exp-31)
+    // rate = (1+(man-2^31)/2^31)*2^exp
+    man = man<<1;
+    man &= 0xffffffffU; // a nop on 32-bit systems
+    // rate = (1+man/2^32)*2^exp
+    
+    // exp is in the range 0 to 31, man is in the range 0 to 2^32-1
+    // time to lose significance... we want m in the range 0 to 2^9-1
+    // rounding presents a minor problem... we first decide which way
+    // we are rounding (based on given rounding direction and possibly
+    // the bits of the mantissa that are to be discarded).
+    
+    switch (r) {
+      case round_down: {
+        // just truncate
+        man = man>>(32-9);
+        break;
+      }
+      case round_up: {
+        // check all bits that we are discarding
+        if (man & (-1>>9)) {
+          man = (man>>(32-9)) + 1;
+          if (man == (1<<9)) {
+            // no need to check for round up outside of range
+            man = 0;
+            exp += 1;
+          }
+        } else {
+          man = (man>>(32-9));
+        }
+        break;
+      }
+      case round_nearest: {
+        // check msb that we are discarding
+        if (man & (1<<(32-9-1))) {
+          man = (man>>(32-9)) + 1;
+          if (man == (1<<9)) {
+            // no need to check for round up outside of range
+            man = 0;
+            exp += 1;
+          }
+        } else {
+          man = (man>>(32-9));
+        }
+        break;
+      }
+    }
+    
+  } else {
+    // zero rate - not representable
+    
+    if (r == round_down) {
+      return -EINVAL;
+    } else {
+      exp = 0;
+      man = 0;
+    }
+    
+  }
+  
+  PRINTD (DBG_QOS, "rate: man=%u, exp=%hu", man, exp);
+  
+  if (bits)
+    *bits = /* (1<<14) | */ (exp<<9) | man;
+  
+  if (actual)
+    *actual = (exp >= 9)
+      ? (1 << exp) + (man << (exp-9))
+      : (1 << exp) + ((man + (1<<(9-exp-1))) >> (9-exp));
+  
+  return 0;
+}
+
+/********** Linux ATM Operations **********/
+
+// some are not yet implemented while others do not make sense for
+// this device
+
+/********** Open a VC **********/
+
+static int amb_open (struct atm_vcc * atm_vcc)
+{
+  int error;
+  
+  struct atm_qos * qos;
+  struct atm_trafprm * txtp;
+  struct atm_trafprm * rxtp;
+  u16 tx_rate_bits;
+  u16 tx_vc_bits = -1; // hush gcc
+  u16 tx_frame_bits = -1; // hush gcc
+  
+  amb_dev * dev = AMB_DEV(atm_vcc->dev);
+  amb_vcc * vcc;
+  unsigned char pool = -1; // hush gcc
+  short vpi = atm_vcc->vpi;
+  int vci = atm_vcc->vci;
+  
+  PRINTD (DBG_FLOW|DBG_VCC, "amb_open %x %x", vpi, vci);
+  
+#ifdef ATM_VPI_UNSPEC
+  // UNSPEC is deprecated, remove this code eventually
+  if (vpi == ATM_VPI_UNSPEC || vci == ATM_VCI_UNSPEC) {
+    PRINTK (KERN_WARNING, "rejecting open with unspecified VPI/VCI (deprecated)");
+    return -EINVAL;
+  }
+#endif
+  
+  if (!(0 <= vpi && vpi < (1<<NUM_VPI_BITS) &&
+        0 <= vci && vci < (1<<NUM_VCI_BITS))) {
+    PRINTD (DBG_WARN|DBG_VCC, "VPI/VCI out of range: %hd/%d", vpi, vci);
+    return -EINVAL;
+  }
+  
+  qos = &atm_vcc->qos;
+  
+  if (qos->aal != ATM_AAL5) {
+    PRINTD (DBG_QOS, "AAL not supported");
+    return -EINVAL;
+  }
+  
+  // traffic parameters
+  
+  PRINTD (DBG_QOS, "TX:");
+  txtp = &qos->txtp;
+  if (txtp->traffic_class != ATM_NONE) {
+    switch (txtp->traffic_class) {
+      case ATM_UBR: {
+        // we take "the PCR" as a rate-cap
+        int pcr = atm_pcr_goal (txtp);
+        if (!pcr) {
+          // no rate cap
+          tx_rate_bits = 0;
+          tx_vc_bits = TX_UBR;
+          tx_frame_bits = TX_FRAME_NOTCAP;
+        } else {
+          rounding r;
+          if (pcr < 0) {
+            r = round_down;
+            pcr = -pcr;
+          } else {
+            r = round_up;
+          }
+          error = make_rate (pcr, r, &tx_rate_bits, NULL);
+          tx_vc_bits = TX_UBR_CAPPED;
+          tx_frame_bits = TX_FRAME_CAPPED;
+        }
+        break;
+      }
+#if 0
+      case ATM_ABR: {
+        pcr = atm_pcr_goal (txtp);
+        PRINTD (DBG_QOS, "pcr goal = %d", pcr);
+        break;
+      }
+#endif
+      default: {
+        // PRINTD (DBG_QOS, "request for non-UBR/ABR denied");
+        PRINTD (DBG_QOS, "request for non-UBR denied");
+        return -EINVAL;
+      }
+    }
+    PRINTD (DBG_QOS, "tx_rate_bits=%hx, tx_vc_bits=%hx",
+            tx_rate_bits, tx_vc_bits);
+  }
+  
+  PRINTD (DBG_QOS, "RX:");
+  rxtp = &qos->rxtp;
+  if (rxtp->traffic_class == ATM_NONE) {
+    // do nothing
+  } else {
+    // choose an RX pool (arranged in increasing size)
+    for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+      if ((unsigned int) rxtp->max_sdu <= dev->rxq[pool].buffer_size) {
+        PRINTD (DBG_VCC|DBG_QOS|DBG_POOL, "chose pool %hu (max_sdu %u <= %u)",
+                pool, rxtp->max_sdu, dev->rxq[pool].buffer_size);
+        break;
+      }
+    if (pool == NUM_RX_POOLS) {
+      PRINTD (DBG_WARN|DBG_VCC|DBG_QOS|DBG_POOL,
+              "no pool suitable for VC (RX max_sdu %d is too large)",
+              rxtp->max_sdu);
+      return -EINVAL;
+    }
+    
+    switch (rxtp->traffic_class) {
+      case ATM_UBR: {
+        break;
+      }
+#if 0
+      case ATM_ABR: {
+        pcr = atm_pcr_goal (rxtp);
+        PRINTD (DBG_QOS, "pcr goal = %d", pcr);
+        break;
+      }
+#endif
+      default: {
+        // PRINTD (DBG_QOS, "request for non-UBR/ABR denied");
+        PRINTD (DBG_QOS, "request for non-UBR denied");
+        return -EINVAL;
+      }
+    }
+  }
+  
+  // get space for our vcc stuff
+  vcc = kmalloc (sizeof(amb_vcc), GFP_KERNEL);
+  if (!vcc) {
+    PRINTK (KERN_ERR, "out of memory!");
+    return -ENOMEM;
+  }
+  atm_vcc->dev_data = (void *) vcc;
+  
+  // no failures beyond this point
+  
+  // we are not really "immediately before allocating the connection
+  // identifier in hardware", but it will just have to do!
+  set_bit(ATM_VF_ADDR,&atm_vcc->flags);
+  
+  if (txtp->traffic_class != ATM_NONE) {
+    command cmd;
+    
+    vcc->tx_frame_bits = tx_frame_bits;
+    
+    down (&dev->vcc_sf);
+    if (dev->rxer[vci]) {
+      // RXer on the channel already, just modify rate...
+      cmd.request = cpu_to_be32 (SRB_MODIFY_VC_RATE);
+      cmd.args.modify_rate.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.modify_rate.rate = cpu_to_be32 (tx_rate_bits << SRB_RATE_SHIFT);
+      while (command_do (dev, &cmd))
+        schedule();
+      // ... and TX flags, preserving the RX pool
+      cmd.request = cpu_to_be32 (SRB_MODIFY_VC_FLAGS);
+      cmd.args.modify_flags.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.modify_flags.flags = cpu_to_be32
+        ( (AMB_VCC(dev->rxer[vci])->rx_info.pool << SRB_POOL_SHIFT)
+          | (tx_vc_bits << SRB_FLAGS_SHIFT) );
+      while (command_do (dev, &cmd))
+        schedule();
+    } else {
+      // no RXer on the channel, just open (with pool zero)
+      cmd.request = cpu_to_be32 (SRB_OPEN_VC);
+      cmd.args.open.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.open.flags = cpu_to_be32 (tx_vc_bits << SRB_FLAGS_SHIFT);
+      cmd.args.open.rate = cpu_to_be32 (tx_rate_bits << SRB_RATE_SHIFT);
+      while (command_do (dev, &cmd))
+        schedule();
+    }
+    dev->txer[vci].tx_present = 1;
+    up (&dev->vcc_sf);
+  }
+  
+  if (rxtp->traffic_class != ATM_NONE) {
+    command cmd;
+    
+    vcc->rx_info.pool = pool;
+    
+    down (&dev->vcc_sf); 
+    /* grow RX buffer pool */
+    if (!dev->rxq[pool].buffers_wanted)
+      dev->rxq[pool].buffers_wanted = rx_lats;
+    dev->rxq[pool].buffers_wanted += 1;
+    fill_rx_pool (dev, pool, GFP_KERNEL);
+    
+    if (dev->txer[vci].tx_present) {
+      // TXer on the channel already
+      // switch (from pool zero) to this pool, preserving the TX bits
+      cmd.request = cpu_to_be32 (SRB_MODIFY_VC_FLAGS);
+      cmd.args.modify_flags.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.modify_flags.flags = cpu_to_be32
+        ( (pool << SRB_POOL_SHIFT)
+          | (dev->txer[vci].tx_vc_bits << SRB_FLAGS_SHIFT) );
+    } else {
+      // no TXer on the channel, open the VC (with no rate info)
+      cmd.request = cpu_to_be32 (SRB_OPEN_VC);
+      cmd.args.open.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.open.flags = cpu_to_be32 (pool << SRB_POOL_SHIFT);
+      cmd.args.open.rate = cpu_to_be32 (0);
+    }
+    while (command_do (dev, &cmd))
+      schedule();
+    // this link allows RX frames through
+    dev->rxer[vci] = atm_vcc;
+    up (&dev->vcc_sf);
+  }
+  
+  // indicate readiness
+  set_bit(ATM_VF_READY,&atm_vcc->flags);
+  
+  return 0;
+}
+
+/********** Close a VC **********/
+
+static void amb_close (struct atm_vcc * atm_vcc) {
+  amb_dev * dev = AMB_DEV (atm_vcc->dev);
+  amb_vcc * vcc = AMB_VCC (atm_vcc);
+  u16 vci = atm_vcc->vci;
+  
+  PRINTD (DBG_VCC|DBG_FLOW, "amb_close");
+  
+  // indicate unreadiness
+  clear_bit(ATM_VF_READY,&atm_vcc->flags);
+  
+  // disable TXing
+  if (atm_vcc->qos.txtp.traffic_class != ATM_NONE) {
+    command cmd;
+    
+    down (&dev->vcc_sf);
+    if (dev->rxer[vci]) {
+      // RXer still on the channel, just modify rate... XXX not really needed
+      cmd.request = cpu_to_be32 (SRB_MODIFY_VC_RATE);
+      cmd.args.modify_rate.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.modify_rate.rate = cpu_to_be32 (0);
+      // ... and clear TX rate flags (XXX to stop RM cell output?), preserving RX pool
+    } else {
+      // no RXer on the channel, close channel
+      cmd.request = cpu_to_be32 (SRB_CLOSE_VC);
+      cmd.args.close.vc = cpu_to_be32 (vci); // vpi 0
+    }
+    dev->txer[vci].tx_present = 0;
+    while (command_do (dev, &cmd))
+      schedule();
+    up (&dev->vcc_sf);
+  }
+  
+  // disable RXing
+  if (atm_vcc->qos.rxtp.traffic_class != ATM_NONE) {
+    command cmd;
+    
+    // this is (the?) one reason why we need the amb_vcc struct
+    unsigned char pool = vcc->rx_info.pool;
+    
+    down (&dev->vcc_sf);
+    if (dev->txer[vci].tx_present) {
+      // TXer still on the channel, just go to pool zero XXX not really needed
+      cmd.request = cpu_to_be32 (SRB_MODIFY_VC_FLAGS);
+      cmd.args.modify_flags.vc = cpu_to_be32 (vci);  // vpi 0
+      cmd.args.modify_flags.flags = cpu_to_be32
+        (dev->txer[vci].tx_vc_bits << SRB_FLAGS_SHIFT);
+    } else {
+      // no TXer on the channel, close the VC
+      cmd.request = cpu_to_be32 (SRB_CLOSE_VC);
+      cmd.args.close.vc = cpu_to_be32 (vci); // vpi 0
+    }
+    // forget the rxer - no more skbs will be pushed
+    if (atm_vcc != dev->rxer[vci])
+      PRINTK (KERN_ERR, "%s vcc=%p rxer[vci]=%p",
+              "arghhh! we're going to die!",
+              vcc, dev->rxer[vci]);
+    dev->rxer[vci] = NULL;
+    while (command_do (dev, &cmd))
+      schedule();
+    
+    /* shrink RX buffer pool */
+    dev->rxq[pool].buffers_wanted -= 1;
+    if (dev->rxq[pool].buffers_wanted == rx_lats) {
+      dev->rxq[pool].buffers_wanted = 0;
+      drain_rx_pool (dev, pool);
+    }
+    up (&dev->vcc_sf);
+  }
+  
+  // free our structure
+  kfree (vcc);
+  
+  // say the VPI/VCI is free again
+  clear_bit(ATM_VF_ADDR,&atm_vcc->flags);
+
+  return;
+}
+
+/********** Set socket options for a VC **********/
+
+// int amb_getsockopt (struct atm_vcc * atm_vcc, int level, int optname, void * optval, int optlen);
+
+/********** Set socket options for a VC **********/
+
+// int amb_setsockopt (struct atm_vcc * atm_vcc, int level, int optname, void * optval, int optlen);
+
+/********** Send **********/
+
+static int amb_send (struct atm_vcc * atm_vcc, struct sk_buff * skb) {
+  amb_dev * dev = AMB_DEV(atm_vcc->dev);
+  amb_vcc * vcc = AMB_VCC(atm_vcc);
+  u16 vc = atm_vcc->vci;
+  unsigned int tx_len = skb->len;
+  unsigned char * tx_data = skb->data;
+  tx_simple * tx_descr;
+  tx_in tx;
+  
+  if (test_bit (dead, &dev->flags))
+    return -EIO;
+  
+  PRINTD (DBG_FLOW|DBG_TX, "amb_send vc %x data %p len %u",
+          vc, tx_data, tx_len);
+  
+  dump_skb (">>>", vc, skb);
+  
+  if (!dev->txer[vc].tx_present) {
+    PRINTK (KERN_ERR, "attempt to send on RX-only VC %x", vc);
+    return -EBADFD;
+  }
+  
+  // this is a driver private field so we have to set it ourselves,
+  // despite the fact that we are _required_ to use it to check for a
+  // pop function
+  ATM_SKB(skb)->vcc = atm_vcc;
+  
+  if (skb->len > (size_t) atm_vcc->qos.txtp.max_sdu) {
+    PRINTK (KERN_ERR, "sk_buff length greater than agreed max_sdu, dropping...");
+    return -EIO;
+  }
+  
+  if (check_area (skb->data, skb->len)) {
+    atomic_inc(&atm_vcc->stats->tx_err);
+    return -ENOMEM; // ?
+  }
+  
+  // allocate memory for fragments
+  tx_descr = kmalloc (sizeof(tx_simple), GFP_KERNEL);
+  if (!tx_descr) {
+    PRINTK (KERN_ERR, "could not allocate TX descriptor");
+    return -ENOMEM;
+  }
+  if (check_area (tx_descr, sizeof(tx_simple))) {
+    kfree (tx_descr);
+    return -ENOMEM;
+  }
+  PRINTD (DBG_TX, "fragment list allocated at %p", tx_descr);
+  
+  tx_descr->skb = skb;
+  
+  tx_descr->tx_frag.bytes = cpu_to_be32 (tx_len);
+  tx_descr->tx_frag.address = cpu_to_be32 (virt_to_bus (tx_data));
+  
+  tx_descr->tx_frag_end.handle = virt_to_bus (tx_descr);
+  tx_descr->tx_frag_end.vc = 0;
+  tx_descr->tx_frag_end.next_descriptor_length = 0;
+  tx_descr->tx_frag_end.next_descriptor = 0;
+#ifdef AMB_NEW_MICROCODE
+  tx_descr->tx_frag_end.cpcs_uu = 0;
+  tx_descr->tx_frag_end.cpi = 0;
+  tx_descr->tx_frag_end.pad = 0;
+#endif
+  
+  tx.vc = cpu_to_be16 (vcc->tx_frame_bits | vc);
+  tx.tx_descr_length = cpu_to_be16 (sizeof(tx_frag)+sizeof(tx_frag_end));
+  tx.tx_descr_addr = cpu_to_be32 (virt_to_bus (&tx_descr->tx_frag));
+  
+  while (tx_give (dev, &tx))
+    schedule();
+  return 0;
+}
+
+/********** Change QoS on a VC **********/
+
+// int amb_change_qos (struct atm_vcc * atm_vcc, struct atm_qos * qos, int flags);
+
+/********** Free RX Socket Buffer **********/
+
+#if 0
+static void amb_free_rx_skb (struct atm_vcc * atm_vcc, struct sk_buff * skb) {
+  amb_dev * dev = AMB_DEV (atm_vcc->dev);
+  amb_vcc * vcc = AMB_VCC (atm_vcc);
+  unsigned char pool = vcc->rx_info.pool;
+  rx_in rx;
+  
+  // This may be unsafe for various reasons that I cannot really guess
+  // at. However, I note that the ATM layer calls kfree_skb rather
+  // than dev_kfree_skb at this point so we are least covered as far
+  // as buffer locking goes. There may be bugs if pcap clones RX skbs.
+
+  PRINTD (DBG_FLOW|DBG_SKB, "amb_rx_free skb %p (atm_vcc %p, vcc %p)",
+          skb, atm_vcc, vcc);
+  
+  rx.handle = virt_to_bus (skb);
+  rx.host_address = cpu_to_be32 (virt_to_bus (skb->data));
+  
+  skb->data = skb->head;
+  skb->tail = skb->head;
+  skb->len = 0;
+  
+  if (!rx_give (dev, &rx, pool)) {
+    // success
+    PRINTD (DBG_SKB|DBG_POOL, "recycled skb for pool %hu", pool);
+    return;
+  }
+  
+  // just do what the ATM layer would have done
+  dev_kfree_skb_any (skb);
+  
+  return;
+}
+#endif
+
+/********** Proc File Output **********/
+
+static int amb_proc_read (struct atm_dev * atm_dev, loff_t * pos, char * page) {
+  amb_dev * dev = AMB_DEV (atm_dev);
+  int left = *pos;
+  unsigned char pool;
+  
+  PRINTD (DBG_FLOW, "amb_proc_read");
+  
+  /* more diagnostics here? */
+  
+  if (!left--) {
+    amb_stats * s = &dev->stats;
+    return sprintf (page,
+                    "frames: TX OK %lu, RX OK %lu, RX bad %lu "
+                    "(CRC %lu, long %lu, aborted %lu, unused %lu).\n",
+                    s->tx_ok, s->rx.ok, s->rx.error,
+                    s->rx.badcrc, s->rx.toolong,
+                    s->rx.aborted, s->rx.unused);
+  }
+  
+  if (!left--) {
+    amb_cq * c = &dev->cq;
+    return sprintf (page, "cmd queue [cur/hi/max]: %u/%u/%u. ",
+                    c->pending, c->high, c->maximum);
+  }
+  
+  if (!left--) {
+    amb_txq * t = &dev->txq;
+    return sprintf (page, "TX queue [cur/max high full]: %u/%u %u %u.\n",
+                    t->pending, t->maximum, t->high, t->filled);
+  }
+  
+  if (!left--) {
+    unsigned int count = sprintf (page, "RX queues [cur/max/req low empty]:");
+    for (pool = 0; pool < NUM_RX_POOLS; ++pool) {
+      amb_rxq * r = &dev->rxq[pool];
+      count += sprintf (page+count, " %u/%u/%u %u %u",
+                        r->pending, r->maximum, r->buffers_wanted, r->low, r->emptied);
+    }
+    count += sprintf (page+count, ".\n");
+    return count;
+  }
+  
+  if (!left--) {
+    unsigned int count = sprintf (page, "RX buffer sizes:");
+    for (pool = 0; pool < NUM_RX_POOLS; ++pool) {
+      amb_rxq * r = &dev->rxq[pool];
+      count += sprintf (page+count, " %u", r->buffer_size);
+    }
+    count += sprintf (page+count, ".\n");
+    return count;
+  }
+  
+#if 0
+  if (!left--) {
+    // suni block etc?
+  }
+#endif
+  
+  return 0;
+}
+
+/********** Operation Structure **********/
+
+static const struct atmdev_ops amb_ops = {
+  .open         = amb_open,
+  .close        = amb_close,
+  .send         = amb_send,
+  .proc_read    = amb_proc_read,
+  .owner        = THIS_MODULE,
+};
+
+/********** housekeeping **********/
+static void do_housekeeping (unsigned long arg) {
+  amb_dev * dev = (amb_dev *) arg;
+  
+  // could collect device-specific (not driver/atm-linux) stats here
+      
+  // last resort refill once every ten seconds
+  fill_rx_pools (dev);
+  mod_timer(&dev->housekeeping, jiffies + 10*HZ);
+  
+  return;
+}
+
+/********** creation of communication queues **********/
+
+static int __devinit create_queues (amb_dev * dev, unsigned int cmds,
+                                 unsigned int txs, unsigned int * rxs,
+                                 unsigned int * rx_buffer_sizes) {
+  unsigned char pool;
+  size_t total = 0;
+  void * memory;
+  void * limit;
+  
+  PRINTD (DBG_FLOW, "create_queues %p", dev);
+  
+  total += cmds * sizeof(command);
+  
+  total += txs * (sizeof(tx_in) + sizeof(tx_out));
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+    total += rxs[pool] * (sizeof(rx_in) + sizeof(rx_out));
+  
+  memory = kmalloc (total, GFP_KERNEL);
+  if (!memory) {
+    PRINTK (KERN_ERR, "could not allocate queues");
+    return -ENOMEM;
+  }
+  if (check_area (memory, total)) {
+    PRINTK (KERN_ERR, "queues allocated in nasty area");
+    kfree (memory);
+    return -ENOMEM;
+  }
+  
+  limit = memory + total;
+  PRINTD (DBG_INIT, "queues from %p to %p", memory, limit);
+  
+  PRINTD (DBG_CMD, "command queue at %p", memory);
+  
+  {
+    command * cmd = memory;
+    amb_cq * cq = &dev->cq;
+    
+    cq->pending = 0;
+    cq->high = 0;
+    cq->maximum = cmds - 1;
+    
+    cq->ptrs.start = cmd;
+    cq->ptrs.in = cmd;
+    cq->ptrs.out = cmd;
+    cq->ptrs.limit = cmd + cmds;
+    
+    memory = cq->ptrs.limit;
+  }
+  
+  PRINTD (DBG_TX, "TX queue pair at %p", memory);
+  
+  {
+    tx_in * in = memory;
+    tx_out * out;
+    amb_txq * txq = &dev->txq;
+    
+    txq->pending = 0;
+    txq->high = 0;
+    txq->filled = 0;
+    txq->maximum = txs - 1;
+    
+    txq->in.start = in;
+    txq->in.ptr = in;
+    txq->in.limit = in + txs;
+    
+    memory = txq->in.limit;
+    out = memory;
+    
+    txq->out.start = out;
+    txq->out.ptr = out;
+    txq->out.limit = out + txs;
+    
+    memory = txq->out.limit;
+  }
+  
+  PRINTD (DBG_RX, "RX queue pairs at %p", memory);
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool) {
+    rx_in * in = memory;
+    rx_out * out;
+    amb_rxq * rxq = &dev->rxq[pool];
+    
+    rxq->buffer_size = rx_buffer_sizes[pool];
+    rxq->buffers_wanted = 0;
+    
+    rxq->pending = 0;
+    rxq->low = rxs[pool] - 1;
+    rxq->emptied = 0;
+    rxq->maximum = rxs[pool] - 1;
+    
+    rxq->in.start = in;
+    rxq->in.ptr = in;
+    rxq->in.limit = in + rxs[pool];
+    
+    memory = rxq->in.limit;
+    out = memory;
+    
+    rxq->out.start = out;
+    rxq->out.ptr = out;
+    rxq->out.limit = out + rxs[pool];
+    
+    memory = rxq->out.limit;
+  }
+  
+  if (memory == limit) {
+    return 0;
+  } else {
+    PRINTK (KERN_ERR, "bad queue alloc %p != %p (tell maintainer)", memory, limit);
+    kfree (limit - total);
+    return -ENOMEM;
+  }
+  
+}
+
+/********** destruction of communication queues **********/
+
+static void destroy_queues (amb_dev * dev) {
+  // all queues assumed empty
+  void * memory = dev->cq.ptrs.start;
+  // includes txq.in, txq.out, rxq[].in and rxq[].out
+  
+  PRINTD (DBG_FLOW, "destroy_queues %p", dev);
+  
+  PRINTD (DBG_INIT, "freeing queues at %p", memory);
+  kfree (memory);
+  
+  return;
+}
+
+/********** basic loader commands and error handling **********/
+// centisecond timeouts - guessing away here
+static unsigned int command_timeouts [] = {
+        [host_memory_test]     = 15,
+        [read_adapter_memory]  = 2,
+        [write_adapter_memory] = 2,
+        [adapter_start]        = 50,
+        [get_version_number]   = 10,
+        [interrupt_host]       = 1,
+        [flash_erase_sector]   = 1,
+        [adap_download_block]  = 1,
+        [adap_erase_flash]     = 1,
+        [adap_run_in_iram]     = 1,
+        [adap_end_download]    = 1
+};
+
+
+static unsigned int command_successes [] = {
+        [host_memory_test]     = COMMAND_PASSED_TEST,
+        [read_adapter_memory]  = COMMAND_READ_DATA_OK,
+        [write_adapter_memory] = COMMAND_WRITE_DATA_OK,
+        [adapter_start]        = COMMAND_COMPLETE,
+        [get_version_number]   = COMMAND_COMPLETE,
+        [interrupt_host]       = COMMAND_COMPLETE,
+        [flash_erase_sector]   = COMMAND_COMPLETE,
+        [adap_download_block]  = COMMAND_COMPLETE,
+        [adap_erase_flash]     = COMMAND_COMPLETE,
+        [adap_run_in_iram]     = COMMAND_COMPLETE,
+        [adap_end_download]    = COMMAND_COMPLETE
+};
+  
+static  int decode_loader_result (loader_command cmd, u32 result)
+{
+        int res;
+        const char *msg;
+
+        if (result == command_successes[cmd])
+                return 0;
+
+        switch (result) {
+                case BAD_COMMAND:
+                        res = -EINVAL;
+                        msg = "bad command";
+                        break;
+                case COMMAND_IN_PROGRESS:
+                        res = -ETIMEDOUT;
+                        msg = "command in progress";
+                        break;
+                case COMMAND_PASSED_TEST:
+                        res = 0;
+                        msg = "command passed test";
+                        break;
+                case COMMAND_FAILED_TEST:
+                        res = -EIO;
+                        msg = "command failed test";
+                        break;
+                case COMMAND_READ_DATA_OK:
+                        res = 0;
+                        msg = "command read data ok";
+                        break;
+                case COMMAND_READ_BAD_ADDRESS:
+                        res = -EINVAL;
+                        msg = "command read bad address";
+                        break;
+                case COMMAND_WRITE_DATA_OK:
+                        res = 0;
+                        msg = "command write data ok";
+                        break;
+                case COMMAND_WRITE_BAD_ADDRESS:
+                        res = -EINVAL;
+                        msg = "command write bad address";
+                        break;
+                case COMMAND_WRITE_FLASH_FAILURE:
+                        res = -EIO;
+                        msg = "command write flash failure";
+                        break;
+                case COMMAND_COMPLETE:
+                        res = 0;
+                        msg = "command complete";
+                        break;
+                case COMMAND_FLASH_ERASE_FAILURE:
+                        res = -EIO;
+                        msg = "command flash erase failure";
+                        break;
+                case COMMAND_WRITE_BAD_DATA:
+                        res = -EINVAL;
+                        msg = "command write bad data";
+                        break;
+                default:
+                        res = -EINVAL;
+                        msg = "unknown error";
+                        PRINTD (DBG_LOAD|DBG_ERR,
+                                "decode_loader_result got %d=%x !",
+                                result, result);
+                        break;
+        }
+
+        PRINTK (KERN_ERR, "%s", msg);
+        return res;
+}
+
+static int __devinit do_loader_command (volatile loader_block * lb,
+                                     const amb_dev * dev, loader_command cmd) {
+  
+  unsigned long timeout;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "do_loader_command");
+  
+  /* do a command
+     
+     Set the return value to zero, set the command type and set the
+     valid entry to the right magic value. The payload is already
+     correctly byte-ordered so we leave it alone. Hit the doorbell
+     with the bus address of this structure.
+     
+  */
+  
+  lb->result = 0;
+  lb->command = cpu_to_be32 (cmd);
+  lb->valid = cpu_to_be32 (DMA_VALID);
+  // dump_registers (dev);
+  // dump_loader_block (lb);
+  wr_mem (dev, offsetof(amb_mem, doorbell), virt_to_bus (lb) & ~onegigmask);
+  
+  timeout = command_timeouts[cmd] * 10;
+  
+  while (!lb->result || lb->result == cpu_to_be32 (COMMAND_IN_PROGRESS))
+    if (timeout) {
+      timeout = msleep_interruptible(timeout);
+    } else {
+      PRINTD (DBG_LOAD|DBG_ERR, "command %d timed out", cmd);
+      dump_registers (dev);
+      dump_loader_block (lb);
+      return -ETIMEDOUT;
+    }
+  
+  if (cmd == adapter_start) {
+    // wait for start command to acknowledge...
+    timeout = 100;
+    while (rd_plain (dev, offsetof(amb_mem, doorbell)))
+      if (timeout) {
+        timeout = msleep_interruptible(timeout);
+      } else {
+        PRINTD (DBG_LOAD|DBG_ERR, "start command did not clear doorbell, res=%08x",
+                be32_to_cpu (lb->result));
+        dump_registers (dev);
+        return -ETIMEDOUT;
+      }
+    return 0;
+  } else {
+    return decode_loader_result (cmd, be32_to_cpu (lb->result));
+  }
+  
+}
+
+/* loader: determine loader version */
+
+static int __devinit get_loader_version (loader_block * lb,
+                                      const amb_dev * dev, u32 * version) {
+  int res;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "get_loader_version");
+  
+  res = do_loader_command (lb, dev, get_version_number);
+  if (res)
+    return res;
+  if (version)
+    *version = be32_to_cpu (lb->payload.version);
+  return 0;
+}
+
+/* loader: write memory data blocks */
+
+static int __devinit loader_write (loader_block * lb,
+                                const amb_dev * dev, const u32 * data,
+                                u32 address, unsigned int count) {
+  unsigned int i;
+  transfer_block * tb = &lb->payload.transfer;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "loader_write");
+  
+  if (count > MAX_TRANSFER_DATA)
+    return -EINVAL;
+  tb->address = cpu_to_be32 (address);
+  tb->count = cpu_to_be32 (count);
+  for (i = 0; i < count; ++i)
+    tb->data[i] = cpu_to_be32 (data[i]);
+  return do_loader_command (lb, dev, write_adapter_memory);
+}
+
+/* loader: verify memory data blocks */
+
+static int __devinit loader_verify (loader_block * lb,
+                                 const amb_dev * dev, const u32 * data,
+                                 u32 address, unsigned int count) {
+  unsigned int i;
+  transfer_block * tb = &lb->payload.transfer;
+  int res;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "loader_verify");
+  
+  if (count > MAX_TRANSFER_DATA)
+    return -EINVAL;
+  tb->address = cpu_to_be32 (address);
+  tb->count = cpu_to_be32 (count);
+  res = do_loader_command (lb, dev, read_adapter_memory);
+  if (!res)
+    for (i = 0; i < count; ++i)
+      if (tb->data[i] != cpu_to_be32 (data[i])) {
+        res = -EINVAL;
+        break;
+      }
+  return res;
+}
+
+/* loader: start microcode */
+
+static int __devinit loader_start (loader_block * lb,
+                                const amb_dev * dev, u32 address) {
+  PRINTD (DBG_FLOW|DBG_LOAD, "loader_start");
+  
+  lb->payload.start = cpu_to_be32 (address);
+  return do_loader_command (lb, dev, adapter_start);
+}
+
+/********** reset card **********/
+
+static inline void sf (const char * msg)
+{
+        PRINTK (KERN_ERR, "self-test failed: %s", msg);
+}
+
+static int amb_reset (amb_dev * dev, int diags) {
+  u32 word;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "amb_reset");
+  
+  word = rd_plain (dev, offsetof(amb_mem, reset_control));
+  // put card into reset state
+  wr_plain (dev, offsetof(amb_mem, reset_control), word | AMB_RESET_BITS);
+  // wait a short while
+  udelay (10);
+#if 1
+  // put card into known good state
+  wr_plain (dev, offsetof(amb_mem, interrupt_control), AMB_DOORBELL_BITS);
+  // clear all interrupts just in case
+  wr_plain (dev, offsetof(amb_mem, interrupt), -1);
+#endif
+  // clear self-test done flag
+  wr_plain (dev, offsetof(amb_mem, mb.loader.ready), 0);
+  // take card out of reset state
+  wr_plain (dev, offsetof(amb_mem, reset_control), word &~ AMB_RESET_BITS);
+  
+  if (diags) { 
+    unsigned long timeout;
+    // 4.2 second wait
+    msleep(4200);
+    // half second time-out
+    timeout = 500;
+    while (!rd_plain (dev, offsetof(amb_mem, mb.loader.ready)))
+      if (timeout) {
+        timeout = msleep_interruptible(timeout);
+      } else {
+        PRINTD (DBG_LOAD|DBG_ERR, "reset timed out");
+        return -ETIMEDOUT;
+      }
+    
+    // get results of self-test
+    // XXX double check byte-order
+    word = rd_mem (dev, offsetof(amb_mem, mb.loader.result));
+    if (word & SELF_TEST_FAILURE) {
+      if (word & GPINT_TST_FAILURE)
+        sf ("interrupt");
+      if (word & SUNI_DATA_PATTERN_FAILURE)
+        sf ("SUNI data pattern");
+      if (word & SUNI_DATA_BITS_FAILURE)
+        sf ("SUNI data bits");
+      if (word & SUNI_UTOPIA_FAILURE)
+        sf ("SUNI UTOPIA interface");
+      if (word & SUNI_FIFO_FAILURE)
+        sf ("SUNI cell buffer FIFO");
+      if (word & SRAM_FAILURE)
+        sf ("bad SRAM");
+      // better return value?
+      return -EIO;
+    }
+    
+  }
+  return 0;
+}
+
+/********** transfer and start the microcode **********/
+
+static int __devinit ucode_init (loader_block * lb, amb_dev * dev) {
+  unsigned int i = 0;
+  unsigned int total = 0;
+  const u32 * pointer = ucode_data;
+  u32 address;
+  unsigned int count;
+  int res;
+  
+  PRINTD (DBG_FLOW|DBG_LOAD, "ucode_init");
+  
+  while (address = ucode_regions[i].start,
+         count = ucode_regions[i].count) {
+    PRINTD (DBG_LOAD, "starting region (%x, %u)", address, count);
+    while (count) {
+      unsigned int words;
+      if (count <= MAX_TRANSFER_DATA)
+        words = count;
+      else
+        words = MAX_TRANSFER_DATA;
+      total += words;
+      res = loader_write (lb, dev, pointer, address, words);
+      if (res)
+        return res;
+      res = loader_verify (lb, dev, pointer, address, words);
+      if (res)
+        return res;
+      count -= words;
+      address += sizeof(u32) * words;
+      pointer += words;
+    }
+    i += 1;
+  }
+  if (*pointer == 0xdeadbeef) {
+    return loader_start (lb, dev, ucode_start);
+  } else {
+    // cast needed as there is no %? for pointer differnces
+    PRINTD (DBG_LOAD|DBG_ERR,
+            "offset=%li, *pointer=%x, address=%x, total=%u",
+            (long) (pointer - ucode_data), *pointer, address, total);
+    PRINTK (KERN_ERR, "incorrect microcode data");
+    return -ENOMEM;
+  }
+}
+
+/********** give adapter parameters **********/
+  
+static inline __be32 bus_addr(void * addr) {
+    return cpu_to_be32 (virt_to_bus (addr));
+}
+
+static int __devinit amb_talk (amb_dev * dev) {
+  adap_talk_block a;
+  unsigned char pool;
+  unsigned long timeout;
+  
+  PRINTD (DBG_FLOW, "amb_talk %p", dev);
+  
+  a.command_start = bus_addr (dev->cq.ptrs.start);
+  a.command_end   = bus_addr (dev->cq.ptrs.limit);
+  a.tx_start      = bus_addr (dev->txq.in.start);
+  a.tx_end        = bus_addr (dev->txq.in.limit);
+  a.txcom_start   = bus_addr (dev->txq.out.start);
+  a.txcom_end     = bus_addr (dev->txq.out.limit);
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool) {
+    // the other "a" items are set up by the adapter
+    a.rec_struct[pool].buffer_start = bus_addr (dev->rxq[pool].in.start);
+    a.rec_struct[pool].buffer_end   = bus_addr (dev->rxq[pool].in.limit);
+    a.rec_struct[pool].rx_start     = bus_addr (dev->rxq[pool].out.start);
+    a.rec_struct[pool].rx_end       = bus_addr (dev->rxq[pool].out.limit);
+    a.rec_struct[pool].buffer_size = cpu_to_be32 (dev->rxq[pool].buffer_size);
+  }
+  
+#ifdef AMB_NEW_MICROCODE
+  // disable fast PLX prefetching
+  a.init_flags = 0;
+#endif
+  
+  // pass the structure
+  wr_mem (dev, offsetof(amb_mem, doorbell), virt_to_bus (&a));
+  
+  // 2.2 second wait (must not touch doorbell during 2 second DMA test)
+  msleep(2200);
+  // give the adapter another half second?
+  timeout = 500;
+  while (rd_plain (dev, offsetof(amb_mem, doorbell)))
+    if (timeout) {
+      timeout = msleep_interruptible(timeout);
+    } else {
+      PRINTD (DBG_INIT|DBG_ERR, "adapter init timed out");
+      return -ETIMEDOUT;
+    }
+  
+  return 0;
+}
+
+// get microcode version
+static void __devinit amb_ucode_version (amb_dev * dev) {
+  u32 major;
+  u32 minor;
+  command cmd;
+  cmd.request = cpu_to_be32 (SRB_GET_VERSION);
+  while (command_do (dev, &cmd)) {
+    set_current_state(TASK_UNINTERRUPTIBLE);
+    schedule();
+  }
+  major = be32_to_cpu (cmd.args.version.major);
+  minor = be32_to_cpu (cmd.args.version.minor);
+  PRINTK (KERN_INFO, "microcode version is %u.%u", major, minor);
+}
+  
+// swap bits within byte to get Ethernet ordering
+static u8 bit_swap (u8 byte)
+{
+    const u8 swap[] = {
+      0x0, 0x8, 0x4, 0xc,
+      0x2, 0xa, 0x6, 0xe,
+      0x1, 0x9, 0x5, 0xd,
+      0x3, 0xb, 0x7, 0xf
+    };
+    return ((swap[byte & 0xf]<<4) | swap[byte>>4]);
+}
+
+// get end station address
+static void __devinit amb_esi (amb_dev * dev, u8 * esi) {
+  u32 lower4;
+  u16 upper2;
+  command cmd;
+  
+  cmd.request = cpu_to_be32 (SRB_GET_BIA);
+  while (command_do (dev, &cmd)) {
+    set_current_state(TASK_UNINTERRUPTIBLE);
+    schedule();
+  }
+  lower4 = be32_to_cpu (cmd.args.bia.lower4);
+  upper2 = be32_to_cpu (cmd.args.bia.upper2);
+  PRINTD (DBG_LOAD, "BIA: lower4: %08x, upper2 %04x", lower4, upper2);
+  
+  if (esi) {
+    unsigned int i;
+    
+    PRINTDB (DBG_INIT, "ESI:");
+    for (i = 0; i < ESI_LEN; ++i) {
+      if (i < 4)
+          esi[i] = bit_swap (lower4>>(8*i));
+      else
+          esi[i] = bit_swap (upper2>>(8*(i-4)));
+      PRINTDM (DBG_INIT, " %02x", esi[i]);
+    }
+    
+    PRINTDE (DBG_INIT, "");
+  }
+  
+  return;
+}
+  
+static void fixup_plx_window (amb_dev *dev, loader_block *lb)
+{
+        // fix up the PLX-mapped window base address to match the block
+        unsigned long blb;
+        u32 mapreg;
+        blb = virt_to_bus(lb);
+        // the kernel stack had better not ever cross a 1Gb boundary!
+        mapreg = rd_plain (dev, offsetof(amb_mem, stuff[10]));
+        mapreg &= ~onegigmask;
+        mapreg |= blb & onegigmask;
+        wr_plain (dev, offsetof(amb_mem, stuff[10]), mapreg);
+        return;
+}
+
+static int __devinit amb_init (amb_dev * dev)
+{
+  loader_block lb;
+  
+  u32 version;
+  
+  if (amb_reset (dev, 1)) {
+    PRINTK (KERN_ERR, "card reset failed!");
+  } else {
+    fixup_plx_window (dev, &lb);
+    
+    if (get_loader_version (&lb, dev, &version)) {
+      PRINTK (KERN_INFO, "failed to get loader version");
+    } else {
+      PRINTK (KERN_INFO, "loader version is %08x", version);
+      
+      if (ucode_init (&lb, dev)) {
+        PRINTK (KERN_ERR, "microcode failure");
+      } else if (create_queues (dev, cmds, txs, rxs, rxs_bs)) {
+        PRINTK (KERN_ERR, "failed to get memory for queues");
+      } else {
+        
+        if (amb_talk (dev)) {
+          PRINTK (KERN_ERR, "adapter did not accept queues");
+        } else {
+          
+          amb_ucode_version (dev);
+          return 0;
+          
+        } /* amb_talk */
+        
+        destroy_queues (dev);
+      } /* create_queues, ucode_init */
+      
+      amb_reset (dev, 0);
+    } /* get_loader_version */
+    
+  } /* amb_reset */
+  
+  return -EINVAL;
+}
+
+static void setup_dev(amb_dev *dev, struct pci_dev *pci_dev) 
+{
+      unsigned char pool;
+      memset (dev, 0, sizeof(amb_dev));
+      
+      // set up known dev items straight away
+      dev->pci_dev = pci_dev; 
+      pci_set_drvdata(pci_dev, dev);
+      
+      dev->iobase = pci_resource_start (pci_dev, 1);
+      dev->irq = pci_dev->irq; 
+      dev->membase = bus_to_virt(pci_resource_start(pci_dev, 0));
+      
+      // flags (currently only dead)
+      dev->flags = 0;
+      
+      // Allocate cell rates (fibre)
+      // ATM_OC3_PCR = 1555200000/8/270*260/53 - 29/53
+      // to be really pedantic, this should be ATM_OC3c_PCR
+      dev->tx_avail = ATM_OC3_PCR;
+      dev->rx_avail = ATM_OC3_PCR;
+      
+#ifdef FILL_RX_POOLS_IN_BH
+      // initialise bottom half
+      INIT_WORK(&dev->bh, (void (*)(void *)) fill_rx_pools, dev);
+#endif
+      
+      // semaphore for txer/rxer modifications - we cannot use a
+      // spinlock as the critical region needs to switch processes
+      init_MUTEX (&dev->vcc_sf);
+      // queue manipulation spinlocks; we want atomic reads and
+      // writes to the queue descriptors (handles IRQ and SMP)
+      // consider replacing "int pending" -> "atomic_t available"
+      // => problem related to who gets to move queue pointers
+      spin_lock_init (&dev->cq.lock);
+      spin_lock_init (&dev->txq.lock);
+      for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+        spin_lock_init (&dev->rxq[pool].lock);
+}
+
+static void setup_pci_dev(struct pci_dev *pci_dev)
+{
+        unsigned char lat;
+      
+        // enable bus master accesses
+        pci_set_master(pci_dev);
+
+        // frobnicate latency (upwards, usually)
+        pci_read_config_byte (pci_dev, PCI_LATENCY_TIMER, &lat);
+
+        if (!pci_lat)
+                pci_lat = (lat < MIN_PCI_LATENCY) ? MIN_PCI_LATENCY : lat;
+
+        if (lat != pci_lat) {
+                PRINTK (KERN_INFO, "Changing PCI latency timer from %hu to %hu",
+                        lat, pci_lat);
+                pci_write_config_byte(pci_dev, PCI_LATENCY_TIMER, pci_lat);
+        }
+}
+
+static int __devinit amb_probe(struct pci_dev *pci_dev, const struct pci_device_id *pci_ent)
+{
+        amb_dev * dev;
+        int err;
+        unsigned int irq;
+      
+        err = pci_enable_device(pci_dev);
+        if (err < 0) {
+                PRINTK (KERN_ERR, "skipped broken (PLX rev 2) card");
+                goto out;
+        }
+
+        // read resources from PCI configuration space
+        irq = pci_dev->irq;
+
+        if (pci_dev->device == PCI_DEVICE_ID_MADGE_AMBASSADOR_BAD) {
+                PRINTK (KERN_ERR, "skipped broken (PLX rev 2) card");
+                err = -EINVAL;
+                goto out_disable;
+        }
+
+        PRINTD (DBG_INFO, "found Madge ATM adapter (amb) at"
+                " IO %lx, IRQ %u, MEM %p", pci_resource_start(pci_dev, 1),
+                irq, bus_to_virt(pci_resource_start(pci_dev, 0)));
+
+        // check IO region
+        err = pci_request_region(pci_dev, 1, DEV_LABEL);
+        if (err < 0) {
+                PRINTK (KERN_ERR, "IO range already in use!");
+                goto out_disable;
+        }
+
+        dev = kmalloc (sizeof(amb_dev), GFP_KERNEL);
+        if (!dev) {
+                PRINTK (KERN_ERR, "out of memory!");
+                err = -ENOMEM;
+                goto out_release;
+        }
+
+        setup_dev(dev, pci_dev);
+
+        err = amb_init(dev);
+        if (err < 0) {
+                PRINTK (KERN_ERR, "adapter initialisation failure");
+                goto out_free;
+        }
+
+        setup_pci_dev(pci_dev);
+
+        // grab (but share) IRQ and install handler
+        err = request_irq(irq, interrupt_handler, SA_SHIRQ, DEV_LABEL, dev);
+        if (err < 0) {
+                PRINTK (KERN_ERR, "request IRQ failed!");
+                goto out_reset;
+        }
+
+        dev->atm_dev = atm_dev_register (DEV_LABEL, &amb_ops, -1, NULL);
+        if (!dev->atm_dev) {
+                PRINTD (DBG_ERR, "failed to register Madge ATM adapter");
+                err = -EINVAL;
+                goto out_free_irq;
+        }
+
+        PRINTD (DBG_INFO, "registered Madge ATM adapter (no. %d) (%p) at %p",
+                dev->atm_dev->number, dev, dev->atm_dev);
+                dev->atm_dev->dev_data = (void *) dev;
+
+        // register our address
+        amb_esi (dev, dev->atm_dev->esi);
+
+        // 0 bits for vpi, 10 bits for vci
+        dev->atm_dev->ci_range.vpi_bits = NUM_VPI_BITS;
+        dev->atm_dev->ci_range.vci_bits = NUM_VCI_BITS;
+
+        init_timer(&dev->housekeeping);
+        dev->housekeeping.function = do_housekeeping;
+        dev->housekeeping.data = (unsigned long) dev;
+        mod_timer(&dev->housekeeping, jiffies);
+
+        // enable host interrupts
+        interrupts_on (dev);
+
+out:
+        return err;
+
+out_free_irq:
+        free_irq(irq, dev);
+out_reset:
+        amb_reset(dev, 0);
+out_free:
+        kfree(dev);
+out_release:
+        pci_release_region(pci_dev, 1);
+out_disable:
+        pci_disable_device(pci_dev);
+        goto out;
+}
+
+
+static void __devexit amb_remove_one(struct pci_dev *pci_dev)
+{
+        struct amb_dev *dev;
+
+        dev = pci_get_drvdata(pci_dev);
+
+        PRINTD(DBG_INFO|DBG_INIT, "closing %p (atm_dev = %p)", dev, dev->atm_dev);
+        del_timer_sync(&dev->housekeeping);
+        // the drain should not be necessary
+        drain_rx_pools(dev);
+        interrupts_off(dev);
+        amb_reset(dev, 0);
+        free_irq(dev->irq, dev);
+        pci_disable_device(pci_dev);
+        destroy_queues(dev);
+        atm_dev_deregister(dev->atm_dev);
+        kfree(dev);
+        pci_release_region(pci_dev, 1);
+}
+
+static void __init amb_check_args (void) {
+  unsigned char pool;
+  unsigned int max_rx_size;
+  
+#ifdef DEBUG_AMBASSADOR
+  PRINTK (KERN_NOTICE, "debug bitmap is %hx", debug &= DBG_MASK);
+#else
+  if (debug)
+    PRINTK (KERN_NOTICE, "no debugging support");
+#endif
+  
+  if (cmds < MIN_QUEUE_SIZE)
+    PRINTK (KERN_NOTICE, "cmds has been raised to %u",
+            cmds = MIN_QUEUE_SIZE);
+  
+  if (txs < MIN_QUEUE_SIZE)
+    PRINTK (KERN_NOTICE, "txs has been raised to %u",
+            txs = MIN_QUEUE_SIZE);
+  
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+    if (rxs[pool] < MIN_QUEUE_SIZE)
+      PRINTK (KERN_NOTICE, "rxs[%hu] has been raised to %u",
+              pool, rxs[pool] = MIN_QUEUE_SIZE);
+  
+  // buffers sizes should be greater than zero and strictly increasing
+  max_rx_size = 0;
+  for (pool = 0; pool < NUM_RX_POOLS; ++pool)
+    if (rxs_bs[pool] <= max_rx_size)
+      PRINTK (KERN_NOTICE, "useless pool (rxs_bs[%hu] = %u)",
+              pool, rxs_bs[pool]);
+    else
+      max_rx_size = rxs_bs[pool];
+  
+  if (rx_lats < MIN_RX_BUFFERS)
+    PRINTK (KERN_NOTICE, "rx_lats has been raised to %u",
+            rx_lats = MIN_RX_BUFFERS);
+  
+  return;
+}
+
+/********** module stuff **********/
+
+MODULE_AUTHOR(maintainer_string);
+MODULE_DESCRIPTION(description_string);
+MODULE_LICENSE("GPL");
+module_param(debug,   ushort, 0644);
+module_param(cmds,    uint, 0);
+module_param(txs,     uint, 0);
+module_param_array(rxs,     uint, NULL, 0);
+module_param_array(rxs_bs,  uint, NULL, 0);
+module_param(rx_lats, uint, 0);
+module_param(pci_lat, byte, 0);
+MODULE_PARM_DESC(debug,   "debug bitmap, see .h file");
+MODULE_PARM_DESC(cmds,    "number of command queue entries");
+MODULE_PARM_DESC(txs,     "number of TX queue entries");
+MODULE_PARM_DESC(rxs,     "number of RX queue entries [" __MODULE_STRING(NUM_RX_POOLS) "]");
+MODULE_PARM_DESC(rxs_bs,  "size of RX buffers [" __MODULE_STRING(NUM_RX_POOLS) "]");
+MODULE_PARM_DESC(rx_lats, "number of extra buffers to cope with RX latencies");
+MODULE_PARM_DESC(pci_lat, "PCI latency in bus cycles");
+
+/********** module entry **********/
+
+static struct pci_device_id amb_pci_tbl[] = {
+        { PCI_VENDOR_ID_MADGE, PCI_DEVICE_ID_MADGE_AMBASSADOR, PCI_ANY_ID, PCI_ANY_ID,
+          0, 0, 0 },
+        { PCI_VENDOR_ID_MADGE, PCI_DEVICE_ID_MADGE_AMBASSADOR_BAD, PCI_ANY_ID, PCI_ANY_ID,
+          0, 0, 0 },
+        { 0, }
+};
+
+MODULE_DEVICE_TABLE(pci, amb_pci_tbl);
+
+static struct pci_driver amb_driver = {
+        .name =         "amb",
+        .probe =        amb_probe,
+        .remove =       __devexit_p(amb_remove_one),
+        .id_table =     amb_pci_tbl,
+};
+
+static int __init amb_module_init (void)
+{
+  PRINTD (DBG_FLOW|DBG_INIT, "init_module");
+  
+  // sanity check - cast needed as printk does not support %Zu
+  if (sizeof(amb_mem) != 4*16 + 4*12) {
+    PRINTK (KERN_ERR, "Fix amb_mem (is %lu words).",
+            (unsigned long) sizeof(amb_mem));
+    return -ENOMEM;
+  }
+  
+  show_version();
+  
+  amb_check_args();
+  
+  // get the juice
+  return pci_register_driver(&amb_driver);
+}
+
+/********** module exit **********/
+
+static void __exit amb_module_exit (void)
+{
+  PRINTD (DBG_FLOW|DBG_INIT, "cleanup_module");
+  
+  return pci_unregister_driver(&amb_driver);
+}
+
+module_init(amb_module_init);
+module_exit(amb_module_exit);