1 files changed, 677 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/iseries/viopath.c b/arch/powerpc/platforms/iseries/viopath.c
new file mode 100644
index 00000000000..2376069cdc1
--- /dev/null
+++ b/arch/powerpc/platforms/iseries/viopath.c
@@ -0,0 +1,677 @@
+/* -*- linux-c -*-
+ *
+ *  iSeries Virtual I/O Message Path code
+ *
+ *  Authors: Dave Boutcher <boutcher@us.ibm.com>
+ *           Ryan Arnold <ryanarn@us.ibm.com>
+ *           Colin Devilbiss <devilbis@us.ibm.com>
+ *
+ * (C) Copyright 2000-2005 IBM Corporation
+ *
+ * This code is used by the iSeries virtual disk, cd,
+ * tape, and console to communicate with OS/400 in another
+ * partition.
+ *
+ * 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) anyu 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
+ *
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/proc_fs.h>
+#include <linux/dma-mapping.h>
+#include <linux/wait.h>
+#include <linux/seq_file.h>
+#include <linux/interrupt.h>
+#include <linux/completion.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <asm/prom.h>
+#include <asm/firmware.h>
+#include <asm/iseries/hv_types.h>
+#include <asm/iseries/hv_lp_event.h>
+#include <asm/iseries/hv_lp_config.h>
+#include <asm/iseries/mf.h>
+#include <asm/iseries/vio.h>
+
+/* Status of the path to each other partition in the system.
+ * This is overkill, since we will only ever establish connections
+ * to our hosting partition and the primary partition on the system.
+ * But this allows for other support in the future.
+ */
+static struct viopathStatus {
+        int isOpen;             /* Did we open the path?            */
+        int isActive;           /* Do we have a mon msg outstanding */
+        int users[VIO_MAX_SUBTYPES];
+        HvLpInstanceId mSourceInst;
+        HvLpInstanceId mTargetInst;
+        int numberAllocated;
+} viopathStatus[HVMAXARCHITECTEDLPS];
+
+static DEFINE_SPINLOCK(statuslock);
+
+/*
+ * For each kind of event we allocate a buffer that is
+ * guaranteed not to cross a page boundary
+ */
+static unsigned char event_buffer[VIO_MAX_SUBTYPES * 256]
+        __attribute__((__aligned__(4096)));
+static atomic_t event_buffer_available[VIO_MAX_SUBTYPES];
+static int event_buffer_initialised;
+
+static void handleMonitorEvent(struct HvLpEvent *event);
+
+/*
+ * We use this structure to handle asynchronous responses.  The caller
+ * blocks on the semaphore and the handler posts the semaphore.  However,
+ * if system_state is not SYSTEM_RUNNING, then wait_atomic is used ...
+ */
+struct alloc_parms {
+        struct completion done;
+        int number;
+        atomic_t wait_atomic;
+        int used_wait_atomic;
+};
+
+/* Put a sequence number in each mon msg.  The value is not
+ * important.  Start at something other than 0 just for
+ * readability.  wrapping this is ok.
+ */
+static u8 viomonseq = 22;
+
+/* Our hosting logical partition.  We get this at startup
+ * time, and different modules access this variable directly.
+ */
+HvLpIndex viopath_hostLp = HvLpIndexInvalid;
+EXPORT_SYMBOL(viopath_hostLp);
+HvLpIndex viopath_ourLp = HvLpIndexInvalid;
+EXPORT_SYMBOL(viopath_ourLp);
+
+/* For each kind of incoming event we set a pointer to a
+ * routine to call.
+ */
+static vio_event_handler_t *vio_handler[VIO_MAX_SUBTYPES];
+
+#define VIOPATH_KERN_WARN       KERN_WARNING "viopath: "
+#define VIOPATH_KERN_INFO       KERN_INFO "viopath: "
+
+static int proc_viopath_show(struct seq_file *m, void *v)
+{
+        char *buf;
+        u16 vlanMap;
+        dma_addr_t handle;
+        HvLpEvent_Rc hvrc;
+        DECLARE_COMPLETION_ONSTACK(done);
+        struct device_node *node;
+        const char *sysid;
+
+        buf = kzalloc(HW_PAGE_SIZE, GFP_KERNEL);
+        if (!buf)
+                return 0;
+
+        handle = iseries_hv_map(buf, HW_PAGE_SIZE, DMA_FROM_DEVICE);
+
+        hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
+                        HvLpEvent_Type_VirtualIo,
+                        viomajorsubtype_config | vioconfigget,
+                        HvLpEvent_AckInd_DoAck, HvLpEvent_AckType_ImmediateAck,
+                        viopath_sourceinst(viopath_hostLp),
+                        viopath_targetinst(viopath_hostLp),
+                        (u64)(unsigned long)&done, VIOVERSION << 16,
+                        ((u64)handle) << 32, HW_PAGE_SIZE, 0, 0);
+
+        if (hvrc != HvLpEvent_Rc_Good)
+                printk(VIOPATH_KERN_WARN "hv error on op %d\n", (int)hvrc);
+
+        wait_for_completion(&done);
+
+        vlanMap = HvLpConfig_getVirtualLanIndexMap();
+
+        buf[HW_PAGE_SIZE-1] = '\0';
+        seq_printf(m, "%s", buf);
+
+        iseries_hv_unmap(handle, HW_PAGE_SIZE, DMA_FROM_DEVICE);
+        kfree(buf);
+
+        seq_printf(m, "AVAILABLE_VETH=%x\n", vlanMap);
+
+        node = of_find_node_by_path("/");
+        sysid = NULL;
+        if (node != NULL)
+                sysid = of_get_property(node, "system-id", NULL);
+
+        if (sysid == NULL)
+                seq_printf(m, "SRLNBR=<UNKNOWN>\n");
+        else
+                /* Skip "IBM," on front of serial number, see dt.c */
+                seq_printf(m, "SRLNBR=%s\n", sysid + 4);
+
+        of_node_put(node);
+
+        return 0;
+}
+
+static int proc_viopath_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, proc_viopath_show, NULL);
+}
+
+static const struct file_operations proc_viopath_operations = {
+        .open           = proc_viopath_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
+static int __init vio_proc_init(void)
+{
+        if (!firmware_has_feature(FW_FEATURE_ISERIES))
+                return 0;
+
+        proc_create("iSeries/config", 0, NULL, &proc_viopath_operations);
+        return 0;
+}
+__initcall(vio_proc_init);
+
+/* See if a given LP is active.  Allow for invalid lps to be passed in
+ * and just return invalid
+ */
+int viopath_isactive(HvLpIndex lp)
+{
+        if (lp == HvLpIndexInvalid)
+                return 0;
+        if (lp < HVMAXARCHITECTEDLPS)
+                return viopathStatus[lp].isActive;
+        else
+                return 0;
+}
+EXPORT_SYMBOL(viopath_isactive);
+
+/*
+ * We cache the source and target instance ids for each
+ * partition.
+ */
+HvLpInstanceId viopath_sourceinst(HvLpIndex lp)
+{
+        return viopathStatus[lp].mSourceInst;
+}
+EXPORT_SYMBOL(viopath_sourceinst);
+
+HvLpInstanceId viopath_targetinst(HvLpIndex lp)
+{
+        return viopathStatus[lp].mTargetInst;
+}
+EXPORT_SYMBOL(viopath_targetinst);
+
+/*
+ * Send a monitor message.  This is a message with the acknowledge
+ * bit on that the other side will NOT explicitly acknowledge.  When
+ * the other side goes down, the hypervisor will acknowledge any
+ * outstanding messages....so we will know when the other side dies.
+ */
+static void sendMonMsg(HvLpIndex remoteLp)
+{
+        HvLpEvent_Rc hvrc;
+
+        viopathStatus[remoteLp].mSourceInst =
+                HvCallEvent_getSourceLpInstanceId(remoteLp,
+                                HvLpEvent_Type_VirtualIo);
+        viopathStatus[remoteLp].mTargetInst =
+                HvCallEvent_getTargetLpInstanceId(remoteLp,
+                                HvLpEvent_Type_VirtualIo);
+
+        /*
+         * Deliberately ignore the return code here.  if we call this
+         * more than once, we don't care.
+         */
+        vio_setHandler(viomajorsubtype_monitor, handleMonitorEvent);
+
+        hvrc = HvCallEvent_signalLpEventFast(remoteLp, HvLpEvent_Type_VirtualIo,
+                        viomajorsubtype_monitor, HvLpEvent_AckInd_DoAck,
+                        HvLpEvent_AckType_DeferredAck,
+                        viopathStatus[remoteLp].mSourceInst,
+                        viopathStatus[remoteLp].mTargetInst,
+                        viomonseq++, 0, 0, 0, 0, 0);
+
+        if (hvrc == HvLpEvent_Rc_Good)
+                viopathStatus[remoteLp].isActive = 1;
+        else {
+                printk(VIOPATH_KERN_WARN "could not connect to partition %d\n",
+                                remoteLp);
+                viopathStatus[remoteLp].isActive = 0;
+        }
+}
+
+static void handleMonitorEvent(struct HvLpEvent *event)
+{
+        HvLpIndex remoteLp;
+        int i;
+
+        /*
+         * This handler is _also_ called as part of the loop
+         * at the end of this routine, so it must be able to
+         * ignore NULL events...
+         */
+        if (!event)
+                return;
+
+        /*
+         * First see if this is just a normal monitor message from the
+         * other partition
+         */
+        if (hvlpevent_is_int(event)) {
+                remoteLp = event->xSourceLp;
+                if (!viopathStatus[remoteLp].isActive)
+                        sendMonMsg(remoteLp);
+                return;
+        }
+
+        /*
+         * This path is for an acknowledgement; the other partition
+         * died
+         */
+        remoteLp = event->xTargetLp;
+        if ((event->xSourceInstanceId != viopathStatus[remoteLp].mSourceInst) ||
+            (event->xTargetInstanceId != viopathStatus[remoteLp].mTargetInst)) {
+                printk(VIOPATH_KERN_WARN "ignoring ack....mismatched instances\n");
+                return;
+        }
+
+        printk(VIOPATH_KERN_WARN "partition %d ended\n", remoteLp);
+
+        viopathStatus[remoteLp].isActive = 0;
+
+        /*
+         * For each active handler, pass them a NULL
+         * message to indicate that the other partition
+         * died
+         */
+        for (i = 0; i < VIO_MAX_SUBTYPES; i++) {
+                if (vio_handler[i] != NULL)
+                        (*vio_handler[i])(NULL);
+        }
+}
+
+int vio_setHandler(int subtype, vio_event_handler_t *beh)
+{
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
+                return -EINVAL;
+        if (vio_handler[subtype] != NULL)
+                return -EBUSY;
+        vio_handler[subtype] = beh;
+        return 0;
+}
+EXPORT_SYMBOL(vio_setHandler);
+
+int vio_clearHandler(int subtype)
+{
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
+                return -EINVAL;
+        if (vio_handler[subtype] == NULL)
+                return -EAGAIN;
+        vio_handler[subtype] = NULL;
+        return 0;
+}
+EXPORT_SYMBOL(vio_clearHandler);
+
+static void handleConfig(struct HvLpEvent *event)
+{
+        if (!event)
+                return;
+        if (hvlpevent_is_int(event)) {
+                printk(VIOPATH_KERN_WARN
+                       "unexpected config request from partition %d",
+                       event->xSourceLp);
+
+                if (hvlpevent_need_ack(event)) {
+                        event->xRc = HvLpEvent_Rc_InvalidSubtype;
+                        HvCallEvent_ackLpEvent(event);
+                }
+                return;
+        }
+
+        complete((struct completion *)event->xCorrelationToken);
+}
+
+/*
+ * Initialization of the hosting partition
+ */
+void vio_set_hostlp(void)
+{
+        /*
+         * If this has already been set then we DON'T want to either change
+         * it or re-register the proc file system
+         */
+        if (viopath_hostLp != HvLpIndexInvalid)
+                return;
+
+        /*
+         * Figure out our hosting partition.  This isn't allowed to change
+         * while we're active
+         */
+        viopath_ourLp = HvLpConfig_getLpIndex();
+        viopath_hostLp = HvLpConfig_getHostingLpIndex(viopath_ourLp);
+
+        if (viopath_hostLp != HvLpIndexInvalid)
+                vio_setHandler(viomajorsubtype_config, handleConfig);
+}
+EXPORT_SYMBOL(vio_set_hostlp);
+
+static void vio_handleEvent(struct HvLpEvent *event)
+{
+        HvLpIndex remoteLp;
+        int subtype = (event->xSubtype & VIOMAJOR_SUBTYPE_MASK)
+                >> VIOMAJOR_SUBTYPE_SHIFT;
+
+        if (hvlpevent_is_int(event)) {
+                remoteLp = event->xSourceLp;
+                /*
+                 * The isActive is checked because if the hosting partition
+                 * went down and came back up it would not be active but it
+                 * would have different source and target instances, in which
+                 * case we'd want to reset them.  This case really protects
+                 * against an unauthorized active partition sending interrupts
+                 * or acks to this linux partition.
+                 */
+                if (viopathStatus[remoteLp].isActive
+                    && (event->xSourceInstanceId !=
+                        viopathStatus[remoteLp].mTargetInst)) {
+                        printk(VIOPATH_KERN_WARN
+                               "message from invalid partition. "
+                               "int msg rcvd, source inst (%d) doesn't match (%d)\n",
+                               viopathStatus[remoteLp].mTargetInst,
+                               event->xSourceInstanceId);
+                        return;
+                }
+
+                if (viopathStatus[remoteLp].isActive
+                    && (event->xTargetInstanceId !=
+                        viopathStatus[remoteLp].mSourceInst)) {
+                        printk(VIOPATH_KERN_WARN
+                               "message from invalid partition. "
+                               "int msg rcvd, target inst (%d) doesn't match (%d)\n",
+                               viopathStatus[remoteLp].mSourceInst,
+                               event->xTargetInstanceId);
+                        return;
+                }
+        } else {
+                remoteLp = event->xTargetLp;
+                if (event->xSourceInstanceId !=
+                    viopathStatus[remoteLp].mSourceInst) {
+                        printk(VIOPATH_KERN_WARN
+                               "message from invalid partition. "
+                               "ack msg rcvd, source inst (%d) doesn't match (%d)\n",
+                               viopathStatus[remoteLp].mSourceInst,
+                               event->xSourceInstanceId);
+                        return;
+                }
+
+                if (event->xTargetInstanceId !=
+                    viopathStatus[remoteLp].mTargetInst) {
+                        printk(VIOPATH_KERN_WARN
+                               "message from invalid partition. "
+                               "viopath: ack msg rcvd, target inst (%d) doesn't match (%d)\n",
+                               viopathStatus[remoteLp].mTargetInst,
+                               event->xTargetInstanceId);
+                        return;
+                }
+        }
+
+        if (vio_handler[subtype] == NULL) {
+                printk(VIOPATH_KERN_WARN
+                       "unexpected virtual io event subtype %d from partition %d\n",
+                       event->xSubtype, remoteLp);
+                /* No handler.  Ack if necessary */
+                if (hvlpevent_is_int(event) && hvlpevent_need_ack(event)) {
+                        event->xRc = HvLpEvent_Rc_InvalidSubtype;
+                        HvCallEvent_ackLpEvent(event);
+                }
+                return;
+        }
+
+        /* This innocuous little line is where all the real work happens */
+        (*vio_handler[subtype])(event);
+}
+
+static void viopath_donealloc(void *parm, int number)
+{
+        struct alloc_parms *parmsp = parm;
+
+        parmsp->number = number;
+        if (parmsp->used_wait_atomic)
+                atomic_set(&parmsp->wait_atomic, 0);
+        else
+                complete(&parmsp->done);
+}
+
+static int allocateEvents(HvLpIndex remoteLp, int numEvents)
+{
+        struct alloc_parms parms;
+
+        if (system_state != SYSTEM_RUNNING) {
+                parms.used_wait_atomic = 1;
+                atomic_set(&parms.wait_atomic, 1);
+        } else {
+                parms.used_wait_atomic = 0;
+                init_completion(&parms.done);
+        }
+        mf_allocate_lp_events(remoteLp, HvLpEvent_Type_VirtualIo, 250,  /* It would be nice to put a real number here! */
+                            numEvents, &viopath_donealloc, &parms);
+        if (system_state != SYSTEM_RUNNING) {
+                while (atomic_read(&parms.wait_atomic))
+                        mb();
+        } else
+                wait_for_completion(&parms.done);
+        return parms.number;
+}
+
+int viopath_open(HvLpIndex remoteLp, int subtype, int numReq)
+{
+        int i;
+        unsigned long flags;
+        int tempNumAllocated;
+
+        if ((remoteLp >= HVMAXARCHITECTEDLPS) || (remoteLp == HvLpIndexInvalid))
+                return -EINVAL;
+
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
+                return -EINVAL;
+
+        spin_lock_irqsave(&statuslock, flags);
+
+        if (!event_buffer_initialised) {
+                for (i = 0; i < VIO_MAX_SUBTYPES; i++)
+                        atomic_set(&event_buffer_available[i], 1);
+                event_buffer_initialised = 1;
+        }
+
+        viopathStatus[remoteLp].users[subtype]++;
+
+        if (!viopathStatus[remoteLp].isOpen) {
+                viopathStatus[remoteLp].isOpen = 1;
+                HvCallEvent_openLpEventPath(remoteLp, HvLpEvent_Type_VirtualIo);
+
+                /*
+                 * Don't hold the spinlock during an operation that
+                 * can sleep.
+                 */
+                spin_unlock_irqrestore(&statuslock, flags);
+                tempNumAllocated = allocateEvents(remoteLp, 1);
+                spin_lock_irqsave(&statuslock, flags);
+
+                viopathStatus[remoteLp].numberAllocated += tempNumAllocated;
+
+                if (viopathStatus[remoteLp].numberAllocated == 0) {
+                        HvCallEvent_closeLpEventPath(remoteLp,
+                                        HvLpEvent_Type_VirtualIo);
+
+                        spin_unlock_irqrestore(&statuslock, flags);
+                        return -ENOMEM;
+                }
+
+                viopathStatus[remoteLp].mSourceInst =
+                        HvCallEvent_getSourceLpInstanceId(remoteLp,
+                                        HvLpEvent_Type_VirtualIo);
+                viopathStatus[remoteLp].mTargetInst =
+                        HvCallEvent_getTargetLpInstanceId(remoteLp,
+                                        HvLpEvent_Type_VirtualIo);
+                HvLpEvent_registerHandler(HvLpEvent_Type_VirtualIo,
+                                          &vio_handleEvent);
+                sendMonMsg(remoteLp);
+                printk(VIOPATH_KERN_INFO "opening connection to partition %d, "
+                                "setting sinst %d, tinst %d\n",
+                                remoteLp, viopathStatus[remoteLp].mSourceInst,
+                                viopathStatus[remoteLp].mTargetInst);
+        }
+
+        spin_unlock_irqrestore(&statuslock, flags);
+        tempNumAllocated = allocateEvents(remoteLp, numReq);
+        spin_lock_irqsave(&statuslock, flags);
+        viopathStatus[remoteLp].numberAllocated += tempNumAllocated;
+        spin_unlock_irqrestore(&statuslock, flags);
+
+        return 0;
+}
+EXPORT_SYMBOL(viopath_open);
+
+int viopath_close(HvLpIndex remoteLp, int subtype, int numReq)
+{
+        unsigned long flags;
+        int i;
+        int numOpen;
+        struct alloc_parms parms;
+
+        if ((remoteLp >= HVMAXARCHITECTEDLPS) || (remoteLp == HvLpIndexInvalid))
+                return -EINVAL;
+
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
+                return -EINVAL;
+
+        spin_lock_irqsave(&statuslock, flags);
+        /*
+         * If the viopath_close somehow gets called before a
+         * viopath_open it could decrement to -1 which is a non
+         * recoverable state so we'll prevent this from
+         * happening.
+         */
+        if (viopathStatus[remoteLp].users[subtype] > 0)
+                viopathStatus[remoteLp].users[subtype]--;
+
+        spin_unlock_irqrestore(&statuslock, flags);
+
+        parms.used_wait_atomic = 0;
+        init_completion(&parms.done);
+        mf_deallocate_lp_events(remoteLp, HvLpEvent_Type_VirtualIo,
+                              numReq, &viopath_donealloc, &parms);
+        wait_for_completion(&parms.done);
+
+        spin_lock_irqsave(&statuslock, flags);
+        for (i = 0, numOpen = 0; i < VIO_MAX_SUBTYPES; i++)
+                numOpen += viopathStatus[remoteLp].users[i];
+
+        if ((viopathStatus[remoteLp].isOpen) && (numOpen == 0)) {
+                printk(VIOPATH_KERN_INFO "closing connection to partition %d\n",
+                                remoteLp);
+
+                HvCallEvent_closeLpEventPath(remoteLp,
+                                             HvLpEvent_Type_VirtualIo);
+                viopathStatus[remoteLp].isOpen = 0;
+                viopathStatus[remoteLp].isActive = 0;
+
+                for (i = 0; i < VIO_MAX_SUBTYPES; i++)
+                        atomic_set(&event_buffer_available[i], 0);
+                event_buffer_initialised = 0;
+        }
+        spin_unlock_irqrestore(&statuslock, flags);
+        return 0;
+}
+EXPORT_SYMBOL(viopath_close);
+
+void *vio_get_event_buffer(int subtype)
+{
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
+                return NULL;
+
+        if (atomic_dec_if_positive(&event_buffer_available[subtype]) == 0)
+                return &event_buffer[subtype * 256];
+        else
+                return NULL;
+}
+EXPORT_SYMBOL(vio_get_event_buffer);
+
+void vio_free_event_buffer(int subtype, void *buffer)
+{
+        subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
+        if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES)) {
+                printk(VIOPATH_KERN_WARN
+                       "unexpected subtype %d freeing event buffer\n", subtype);
+                return;
+        }
+
+        if (atomic_read(&event_buffer_available[subtype]) != 0) {
+                printk(VIOPATH_KERN_WARN
+                       "freeing unallocated event buffer, subtype %d\n",
+                       subtype);
+                return;
+        }
+
+        if (buffer != &event_buffer[subtype * 256]) {
+                printk(VIOPATH_KERN_WARN
+                       "freeing invalid event buffer, subtype %d\n", subtype);
+        }
+
+        atomic_set(&event_buffer_available[subtype], 1);
+}
+EXPORT_SYMBOL(vio_free_event_buffer);
+
+static const struct vio_error_entry vio_no_error =
+    { 0, 0, "Non-VIO Error" };
+static const struct vio_error_entry vio_unknown_error =
+    { 0, EIO, "Unknown Error" };
+
+static const struct vio_error_entry vio_default_errors[] = {
+        {0x0001, EIO, "No Connection"},
+        {0x0002, EIO, "No Receiver"},
+        {0x0003, EIO, "No Buffer Available"},
+        {0x0004, EBADRQC, "Invalid Message Type"},
+        {0x0000, 0, NULL},
+};
+
+const struct vio_error_entry *vio_lookup_rc(
+                const struct vio_error_entry *local_table, u16 rc)
+{
+        const struct vio_error_entry *cur;
+
+        if (!rc)
+                return &vio_no_error;
+        if (local_table)
+                for (cur = local_table; cur->rc; ++cur)
+                        if (cur->rc == rc)
+                                return cur;
+        for (cur = vio_default_errors; cur->rc; ++cur)
+                if (cur->rc == rc)
+                        return cur;
+        return &vio_unknown_error;
+}
+EXPORT_SYMBOL(vio_lookup_rc);