firewire: add isochronous multichannel reception

This adds the DMA context programming and userspace ABI for multichannel
reception, i.e. for listening on multiple channel numbers by means of a
single DMA context.

The use case is reception of more streams than there are IR DMA units
offered by the link layer.  This is already implemented by the older
ohci1394 + ieee1394 + raw1394 stack.  And as discussed recently on
linux1394-devel, this feature is occasionally used in practice.

The big drawbacks of this mode are that buffer layout and interrupt
generation necessarily differ from single-channel reception:  Headers
and trailers are not stripped from packets, packets are not aligned with
buffer chunks, interrupts are per buffer chunk, not per packet.

These drawbacks also cause a rather hefty code footprint to support this
rarely used OHCI-1394 feature.  (367 lines added, among them 94 lines of
added userspace ABI documentation.)

This implementation enforces that a multichannel reception context may
only listen to channels to which no single-channel context on the same
link layer is presently listening to.  OHCI-1394 would allow to overlay
single-channel contexts by the multi-channel context, but this would be
a departure from the present first-come-first-served policy of IR
context creation.

The implementation is heavily based on an earlier one by Jay Fenlason.
Thanks Jay.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 72 insertions, 21 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index cf989e1635e1..ba23646bb108 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -193,6 +193,11 @@ struct iso_interrupt_event {
         struct fw_cdev_event_iso_interrupt interrupt;
 };
 
+struct iso_interrupt_mc_event {
+        struct event event;
+        struct fw_cdev_event_iso_interrupt_mc interrupt;
+};
+
 struct iso_resource_event {
         struct event event;
         struct fw_cdev_event_iso_resource iso_resource;
@@ -415,6 +420,7 @@ union ioctl_arg {
         struct fw_cdev_get_cycle_timer2         get_cycle_timer2;
         struct fw_cdev_send_phy_packet          send_phy_packet;
         struct fw_cdev_receive_phy_packets      receive_phy_packets;
+        struct fw_cdev_set_iso_channels         set_iso_channels;
 };
 
 static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
@@ -932,26 +938,54 @@ static void iso_callback(struct fw_iso_context *context, u32 cycle,
                     sizeof(e->interrupt) + header_length, NULL, 0);
 }
 
+static void iso_mc_callback(struct fw_iso_context *context,
+                            dma_addr_t completed, void *data)
+{
+        struct client *client = data;
+        struct iso_interrupt_mc_event *e;
+
+        e = kmalloc(sizeof(*e), GFP_ATOMIC);
+        if (e == NULL) {
+                fw_notify("Out of memory when allocating event\n");
+                return;
+        }
+        e->interrupt.type      = FW_CDEV_EVENT_ISO_INTERRUPT_MULTICHANNEL;
+        e->interrupt.closure   = client->iso_closure;
+        e->interrupt.completed = fw_iso_buffer_lookup(&client->buffer,
+                                                      completed);
+        queue_event(client, &e->event, &e->interrupt,
+                    sizeof(e->interrupt), NULL, 0);
+}
+
 static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
 {
         struct fw_cdev_create_iso_context *a = &arg->create_iso_context;
         struct fw_iso_context *context;
+        fw_iso_callback_t cb;
 
         BUILD_BUG_ON(FW_CDEV_ISO_CONTEXT_TRANSMIT != FW_ISO_CONTEXT_TRANSMIT ||
-                     FW_CDEV_ISO_CONTEXT_RECEIVE  != FW_ISO_CONTEXT_RECEIVE);
-
-        if (a->channel > 63)
-                return -EINVAL;
+                     FW_CDEV_ISO_CONTEXT_RECEIVE  != FW_ISO_CONTEXT_RECEIVE  ||
+                     FW_CDEV_ISO_CONTEXT_RECEIVE_MULTICHANNEL !=
+                                        FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL);
 
         switch (a->type) {
-        case FW_ISO_CONTEXT_RECEIVE:
-                if (a->header_size < 4 || (a->header_size & 3))
+        case FW_ISO_CONTEXT_TRANSMIT:
+                if (a->speed > SCODE_3200 || a->channel > 63)
                         return -EINVAL;
+
+                cb = iso_callback;
                 break;
 
-        case FW_ISO_CONTEXT_TRANSMIT:
-                if (a->speed > SCODE_3200)
+        case FW_ISO_CONTEXT_RECEIVE:
+                if (a->header_size < 4 || (a->header_size & 3) ||
+                    a->channel > 63)
                         return -EINVAL;
+
+                cb = iso_callback;
+                break;
+
+        case FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL:
+                cb = (fw_iso_callback_t)iso_mc_callback;
                 break;
 
         default:
@@ -959,8 +993,7 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
         }
 
         context = fw_iso_context_create(client->device->card, a->type,
-                                        a->channel, a->speed, a->header_size,
-                                        iso_callback, client);
+                        a->channel, a->speed, a->header_size, cb, client);
         if (IS_ERR(context))
                 return PTR_ERR(context);
 
@@ -980,6 +1013,17 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
         return 0;
 }
 
+static int ioctl_set_iso_channels(struct client *client, union ioctl_arg *arg)
+{
+        struct fw_cdev_set_iso_channels *a = &arg->set_iso_channels;
+        struct fw_iso_context *ctx = client->iso_context;
+
+        if (ctx == NULL || a->handle != 0)
+                return -EINVAL;
+
+        return fw_iso_context_set_channels(ctx, &a->channels);
+}
+
 /* Macros for decoding the iso packet control header. */
 #define GET_PAYLOAD_LENGTH(v)   ((v) & 0xffff)
 #define GET_INTERRUPT(v)        (((v) >> 16) & 0x01)
@@ -993,7 +1037,7 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
         struct fw_cdev_queue_iso *a = &arg->queue_iso;
         struct fw_cdev_iso_packet __user *p, *end, *next;
         struct fw_iso_context *ctx = client->iso_context;
-        unsigned long payload, buffer_end, transmit_header_bytes;
+        unsigned long payload, buffer_end, transmit_header_bytes = 0;
         u32 control;
         int count;
         struct {
@@ -1013,7 +1057,6 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
          * use the indirect payload, the iso buffer need not be mapped
          * and the a->data pointer is ignored.
          */
-
         payload = (unsigned long)a->data - client->vm_start;
         buffer_end = client->buffer.page_count << PAGE_SHIFT;
         if (a->data == 0 || client->buffer.pages == NULL ||
@@ -1022,8 +1065,10 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
                 buffer_end = 0;
         }
 
-        p = (struct fw_cdev_iso_packet __user *)u64_to_uptr(a->packets);
+        if (ctx->type == FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL && payload & 3)
+                return -EINVAL;
 
+        p = (struct fw_cdev_iso_packet __user *)u64_to_uptr(a->packets);
         if (!access_ok(VERIFY_READ, p, a->size))
                 return -EFAULT;
 
@@ -1039,19 +1084,24 @@ static int ioctl_queue_iso(struct client *client, union ioctl_arg *arg)
                 u.packet.sy = GET_SY(control);
                 u.packet.header_length = GET_HEADER_LENGTH(control);
 
-                if (ctx->type == FW_ISO_CONTEXT_TRANSMIT) {
-                        if (u.packet.header_length % 4 != 0)
+                switch (ctx->type) {
+                case FW_ISO_CONTEXT_TRANSMIT:
+                        if (u.packet.header_length & 3)
                                 return -EINVAL;
                         transmit_header_bytes = u.packet.header_length;
-                } else {
-                        /*
-                         * We require that header_length is a multiple of
-                         * the fixed header size, ctx->header_size.
-                         */
+                        break;
+
+                case FW_ISO_CONTEXT_RECEIVE:
                         if (u.packet.header_length == 0 ||
                             u.packet.header_length % ctx->header_size != 0)
                                 return -EINVAL;
-                        transmit_header_bytes = 0;
+                        break;
+
+                case FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL:
+                        if (u.packet.payload_length == 0 ||
+                            u.packet.payload_length & 3)
+                                return -EINVAL;
+                        break;
                 }
 
                 next = (struct fw_cdev_iso_packet __user *)
@@ -1534,6 +1584,7 @@ static int (* const ioctl_handlers[])(struct client *, union ioctl_arg *) = {
         [0x14] = ioctl_get_cycle_timer2,
         [0x15] = ioctl_send_phy_packet,
         [0x16] = ioctl_receive_phy_packets,
+        [0x17] = ioctl_set_iso_channels,
 };
 
 static int dispatch_ioctl(struct client *client,