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authorTakashi Iwai <tiwai@suse.de>2009-09-04 06:19:36 -0400
committerTakashi Iwai <tiwai@suse.de>2009-09-07 03:01:10 -0400
commita68c4d11336610dc348620766119db09675707c2 (patch)
tree5d12014b8547f6dd13281cd1b6be2bd3d38adfa9 /Documentation
parentb5d10781731ece07bb2049e7743907194a5cc3f1 (diff)
ALSA: dummy - Fake buffer allocations
Instead of allocating the real buffers, use a fake buffer and ignore read/write in the dummy driver so that we can save the resources. For mmap, a single page (unique to the direction, though) is reused to all buffers. When the app requires to read/write the real buffers, pass fake_buffer=0 module option at loading time. This will get back to the old behavior. Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/sound/alsa/ALSA-Configuration.txt7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt
index bb488b575def..ea16e7d184a4 100644
--- a/Documentation/sound/alsa/ALSA-Configuration.txt
+++ b/Documentation/sound/alsa/ALSA-Configuration.txt
@@ -518,6 +518,7 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
518 pcm_substreams - Number of PCM substreams assigned to each PCM 518 pcm_substreams - Number of PCM substreams assigned to each PCM
519 (default = 8, up to 16) 519 (default = 8, up to 16)
520 hrtimer - Use hrtimer (=1, default) or system timer (=0) 520 hrtimer - Use hrtimer (=1, default) or system timer (=0)
521 fake_buffer - Fake buffer allocations (default = 1)
521 522
522 When multiple PCM devices are created, snd-dummy gives different 523 When multiple PCM devices are created, snd-dummy gives different
523 behavior to each PCM device: 524 behavior to each PCM device:
@@ -526,6 +527,12 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
526 2 = interleaved without mmap 527 2 = interleaved without mmap
527 3 = non-interleaved without mmap 528 3 = non-interleaved without mmap
528 529
530 As default, snd-dummy drivers doesn't allocate the real buffers
531 but either ignores read/write or mmap a single dummy page to all
532 buffer pages, in order to save the resouces. If your apps need
533 the read/ written buffer data to be consistent, pass fake_buffer=0
534 option.
535
529 The power-management is supported. 536 The power-management is supported.
530 537
531 Module snd-echo3g 538 Module snd-echo3g