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In recent commit for ALSA PCM core, some arrangement is done for 'struct snd_pcm_ops.ack' callback. This is called when appl_ptr is explicitly moved in intermediate buffer for PCM frames, except for some cases described later. For drivers in ALSA firewire stack, usage of this callback has a merit to reduce latency between time of PCM frame queueing and handling actual packets in recent isochronous cycle, because no need to wait for software IRQ context from isochronous context of OHCI 1394. If this works well in a case that mapped page frame is used for the intermediate buffer, user process should execute some commands for ioctl(2) to tell the number of handled PCM frames in the intermediate buffer just after handling them. Therefore, at present, with a combination of below conditions, this doesn't work as expected and user process should wait for the software IRQ context as usual: - when ALSA PCM core judges page frame mapping is available for status data (struct snd_pcm_mmap_status) and control data (struct snd_pcm_mmap_control). - user process handles PCM frames by loop just with 'snd_pcm_mmap_begin()' and 'snd_pcm_mmap_commit()'. - user process uses PCM hw plugin in alsa-lib to operate I/O without 'sync_ptr_ioctl' option. Unfortunately, major use case include these three conditions. Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de> |
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| .. | ||
| amdtp-motu-trace.h | ||
| amdtp-motu.c | ||
| Makefile | ||
| motu-hwdep.c | ||
| motu-midi.c | ||
| motu-pcm.c | ||
| motu-proc.c | ||
| motu-protocol-v2.c | ||
| motu-protocol-v3.c | ||
| motu-stream.c | ||
| motu-transaction.c | ||
| motu.c | ||
| motu.h | ||