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In current implementation, when opening a PCM substream, it's needed to check whether the opposite PCM substream runs. This is to assign effectual constraints (e.g. sampling rate) to opened PCM substream. The number of PCM substreams on AMDTP streams in domain is recorded in own structure. Usage of this count is an alternative of the above check. This is better because the count is incremented in pcm.hw_params earlier than pcm.trigger. This commit replaces the check with the substream count and the value for the size of PCM period. Unlike the other drivers in ALSA firewire stack, no MIDI substream is multiplexed into AMDTP stream. I note that Fireface AMDTP protocol has a quirk that tx stream includes blank isochronous cycle. The packet for blank cycle is equivalent to empty or NODATA packet in IEC 61883-6, thus the protocol is similar to blocking transmission method of IEC 61883-6. On the other hand, rx stream adopts non-blocking transmission method. Although the difference of transmission method between tx/rx streams precisely brings different timing for a certain amount of events due to their different calculation for data blocks per packet, it's possible to approximate enough amount of events mostly has the same timing. Actually current ALSA IEC 61883-1/6 engine uses large amount of data blocks for each hardware IRQ (=16 packets). Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Link: https://lore.kernel.org/r/20191007110532.30270-18-o-takashi@sakamocchi.jp Signed-off-by: Takashi Iwai <tiwai@suse.de> |
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| .. | ||
| amdtp-ff.c | ||
| ff-hwdep.c | ||
| ff-midi.c | ||
| ff-pcm.c | ||
| ff-proc.c | ||
| ff-protocol-former.c | ||
| ff-protocol-latter.c | ||
| ff-stream.c | ||
| ff-transaction.c | ||
| ff.c | ||
| ff.h | ||
| Makefile | ||