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-rw-r--r--Documentation/sound/alsa/Procfile.txt36
1 files changed, 22 insertions, 14 deletions
diff --git a/Documentation/sound/alsa/Procfile.txt b/Documentation/sound/alsa/Procfile.txt
index cfac20cf9e3..381908d8ca4 100644
--- a/Documentation/sound/alsa/Procfile.txt
+++ b/Documentation/sound/alsa/Procfile.txt
@@ -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
-
- # cat 2 > /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
+ 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 5 > /proc/asound/card0/pcm0p/xrun_debug
+
+ 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.