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, 19 insertions, 10 deletions

diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index d974aa4a24c9..1cd637ef62d2 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -372,17 +372,19 @@ void fw_core_remove_descriptor(struct fw_descriptor *desc);
  * scatter-gather streaming (e.g. assembling video frame automatically).
  */
 struct fw_iso_packet {
-        u16 payload_length;     /* Length of indirect payload. */
-        u32 interrupt:1;        /* Generate interrupt on this packet */
-        u32 skip:1;             /* Set to not send packet at all. */
-        u32 tag:2;
-        u32 sy:4;
-        u32 header_length:8;    /* Length of immediate header. */
-        u32 header[0];
+        u16 payload_length;     /* Length of indirect payload           */
+        u32 interrupt:1;        /* Generate interrupt on this packet    */
+        u32 skip:1;             /* tx: Set to not send packet at all    */
+                                /* rx: Sync bit, wait for matching sy   */
+        u32 tag:2;              /* tx: Tag in packet header             */
+        u32 sy:4;               /* tx: Sy in packet header              */
+        u32 header_length:8;    /* Length of immediate header           */
+        u32 header[0];          /* tx: Top of 1394 isoch. data_block    */
 };
 
-#define FW_ISO_CONTEXT_TRANSMIT 0
-#define FW_ISO_CONTEXT_RECEIVE  1
+#define FW_ISO_CONTEXT_TRANSMIT                 0
+#define FW_ISO_CONTEXT_RECEIVE                  1
+#define FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL     2
 
 #define FW_ISO_CONTEXT_MATCH_TAG0        1
 #define FW_ISO_CONTEXT_MATCH_TAG1        2
@@ -406,24 +408,31 @@ struct fw_iso_buffer {
 int fw_iso_buffer_init(struct fw_iso_buffer *buffer, struct fw_card *card,
                        int page_count, enum dma_data_direction direction);
 void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer, struct fw_card *card);
+size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed);
 
 struct fw_iso_context;
 typedef void (*fw_iso_callback_t)(struct fw_iso_context *context,
                                   u32 cycle, size_t header_length,
                                   void *header, void *data);
+typedef void (*fw_iso_mc_callback_t)(struct fw_iso_context *context,
+                                     dma_addr_t completed, void *data);
 struct fw_iso_context {
         struct fw_card *card;
         int type;
         int channel;
         int speed;
         size_t header_size;
-        fw_iso_callback_t callback;
+        union {
+                fw_iso_callback_t sc;
+                fw_iso_mc_callback_t mc;
+        } callback;
         void *callback_data;
 };
 
 struct fw_iso_context *fw_iso_context_create(struct fw_card *card,
                 int type, int channel, int speed, size_t header_size,
                 fw_iso_callback_t callback, void *callback_data);
+int fw_iso_context_set_channels(struct fw_iso_context *ctx, u64 *channels);
 int fw_iso_context_queue(struct fw_iso_context *ctx,
                          struct fw_iso_packet *packet,
                          struct fw_iso_buffer *buffer,