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ALSA: pcm - Update document about xrun_debug proc file 

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2009-06-11 16:14:11 +02:00
parent c00701101b
commit 4f64e15019
1 changed files with 20 additions and 12 deletions
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32
Documentation/sound/alsa/Procfile.txt
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@ -88,26 +88,34 @@ card*/pcm*/info
substreams, etc. substreams, etc.
card*/pcm*/xrun_debug card*/pcm*/xrun_debug
This file appears when CONFIG_SND_DEBUG=y. This file appears when CONFIG_SND_DEBUG=y and
This shows the status of xrun (= buffer overrun/xrun) debug of CONFIG_PCM_XRUN_DEBUG=y.
ALSA PCM middle layer, as an integer from 0 to 2. The value This shows the status of xrun (= buffer overrun/xrun) and
can be changed by writing to this file, such as invalid PCM position debug/check of ALSA PCM middle layer.
It takes an integer value, can be changed by writing to this
file, such as
# cat 2 > /proc/asound/card0/pcm0p/xrun_debug # cat 5 > /proc/asound/card0/pcm0p/xrun_debug
When this value is greater than 0, the driver will show the The value consists of the following bit flags:
messages to kernel log when an xrun is detected. The debug bit 0 = Enable XRUN/jiffies debug messages
message is shown also when the invalid H/W pointer is detected bit 1 = Show stack trace at XRUN / jiffies check
at the update of periods (usually called from the interrupt bit 2 = Enable additional jiffies check
When the bit 0 is set, the driver will show the messages to
kernel log when an xrun is detected. The debug message is
shown also when the invalid H/W pointer is detected at the
update of periods (usually called from the interrupt
handler). handler).
When this value is greater than 1, the driver will show the When the bit 1 is set, the driver will show the stack trace
stack trace additionally. This may help the debugging. additionally. This may help the debugging.
Since 2.6.30, this option also enables the hwptr check using Since 2.6.30, this option can enable the hwptr check using
jiffies. This detects spontaneous invalid pointer callback jiffies. This detects spontaneous invalid pointer callback
values, but can be lead to too much corrections for a (mostly values, but can be lead to too much corrections for a (mostly
buggy) hardware that doesn't give smooth pointer updates. buggy) hardware that doesn't give smooth pointer updates.
This feature is enabled via the bit 2.
card*/pcm*/sub*/info card*/pcm*/sub*/info
The general information of this PCM sub-stream. The general information of this PCM sub-stream.