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firewire: add isochronous multichannel reception

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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>
This commit is contained in:
Stefan Richter
2010-07-29 18:19:22 +02:00
parent ae2a976614
commit 872e330e38
6 changed files with 561 additions and 194 deletions
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29
include/linux/firewire.h
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@@ -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,