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