From 872e330e38806d835bd6c311c93ab998e2fb9058 Mon Sep 17 00:00:00 2001 From: Stefan Richter Date: Thu, 29 Jul 2010 18:19:22 +0200 Subject: 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 --- drivers/firewire/core.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/firewire/core.h') diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h index 28621e44b11..e6239f971be 100644 --- a/drivers/firewire/core.h +++ b/drivers/firewire/core.h @@ -90,6 +90,8 @@ struct fw_card_driver { int (*start_iso)(struct fw_iso_context *ctx, s32 cycle, u32 sync, u32 tags); + int (*set_iso_channels)(struct fw_iso_context *ctx, u64 *channels); + int (*queue_iso)(struct fw_iso_context *ctx, struct fw_iso_packet *packet, struct fw_iso_buffer *buffer, -- cgit v1.2.3