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authorTakashi Sakamoto <o-takashi@sakamocchi.jp>2017-06-07 03:38:05 +0300
committerTakashi Iwai <tiwai@suse.de>2017-06-07 08:53:32 +0300
commit875becf8412c60ffae93c5f69e95a4d023f0e8ee (patch)
tree04baa851c60f7c068d8b8218aeea20947cd40ba7 /sound/firewire/amdtp-stream.h
parentf7a478178a8ea970abd34f7ab73e66c9119b1606 (diff)
downloadlinux-875becf8412c60ffae93c5f69e95a4d023f0e8ee.tar.xz
ALSA: firewire: process packets in 'struct snd_pcm_ops.ack' callback
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>
Diffstat (limited to 'sound/firewire/amdtp-stream.h')
-rw-r--r--sound/firewire/amdtp-stream.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/sound/firewire/amdtp-stream.h b/sound/firewire/amdtp-stream.h
index 7e8831722821..6d613f2eb612 100644
--- a/sound/firewire/amdtp-stream.h
+++ b/sound/firewire/amdtp-stream.h
@@ -168,6 +168,7 @@ int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s,
void amdtp_stream_pcm_prepare(struct amdtp_stream *s);
unsigned long amdtp_stream_pcm_pointer(struct amdtp_stream *s);
+int amdtp_stream_pcm_ack(struct amdtp_stream *s);
void amdtp_stream_pcm_abort(struct amdtp_stream *s);
extern const unsigned int amdtp_syt_intervals[CIP_SFC_COUNT];