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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.
card*/pcm*/xrun_debug
This file appears when CONFIG_SND_DEBUG=y.
This shows the status of xrun (= buffer overrun/xrun) debug of
ALSA PCM middle layer, as an integer from 0 to 2. The value
can be changed by writing to this file, such as
This file appears when CONFIG_SND_DEBUG=y and
CONFIG_PCM_XRUN_DEBUG=y.
This shows the status of xrun (= buffer overrun/xrun) and
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
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
The value consists of the following bit flags:
bit 0 = Enable XRUN/jiffies debug messages
bit 1 = Show stack trace at XRUN / jiffies check
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).
When this value is greater than 1, the driver will show the
stack trace additionally. This may help the debugging.
When the bit 1 is set, the driver will show the stack trace
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
values, but can be lead to too much corrections for a (mostly
buggy) hardware that doesn't give smooth pointer updates.
This feature is enabled via the bit 2.
card*/pcm*/sub*/info
The general information of this PCM sub-stream.