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authorTakashi Iwai <tiwai@suse.de>2009-06-11 10:14:11 -0400
committerTakashi Iwai <tiwai@suse.de>2009-06-11 10:14:11 -0400
commit4f64e150191bfddc7f5c0768f325f747dbca1913 (patch)
tree02a13cf25d495c12a66cf18d346c8ccdd608a162 /Documentation/sound
parentc00701101b82f2bc61dfc259748ec6e5288af6a9 (diff)
ALSA: pcm - Update document about xrun_debug proc file
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/sound')
-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 cfac20cf9e33..381908d8ca42 100644
--- a/Documentation/sound/alsa/Procfile.txt
+++ b/Documentation/sound/alsa/Procfile.txt
@@ -88,26 +88,34 @@ card*/pcm*/info
88 substreams, etc. 88 substreams, etc.
89 89
90card*/pcm*/xrun_debug 90card*/pcm*/xrun_debug
91 This file appears when CONFIG_SND_DEBUG=y. 91 This file appears when CONFIG_SND_DEBUG=y and
92 This shows the status of xrun (= buffer overrun/xrun) debug of 92 CONFIG_PCM_XRUN_DEBUG=y.
93 ALSA PCM middle layer, as an integer from 0 to 2. The value 93 This shows the status of xrun (= buffer overrun/xrun) and
94 can be changed by writing to this file, such as 94 invalid PCM position debug/check of ALSA PCM middle layer.
95 95 It takes an integer value, can be changed by writing to this
96 # cat 2 > /proc/asound/card0/pcm0p/xrun_debug 96 file, such as
97 97
98 When this value is greater than 0, the driver will show the 98 # cat 5 > /proc/asound/card0/pcm0p/xrun_debug
99 messages to kernel log when an xrun is detected. The debug 99
100 message is shown also when the invalid H/W pointer is detected 100 The value consists of the following bit flags:
101 at the update of periods (usually called from the interrupt 101 bit 0 = Enable XRUN/jiffies debug messages
102 bit 1 = Show stack trace at XRUN / jiffies check
103 bit 2 = Enable additional jiffies check
104
105 When the bit 0 is set, the driver will show the messages to
106 kernel log when an xrun is detected. The debug message is
107 shown also when the invalid H/W pointer is detected at the
108 update of periods (usually called from the interrupt
102 handler). 109 handler).
103 110
104 When this value is greater than 1, the driver will show the 111 When the bit 1 is set, the driver will show the stack trace
105 stack trace additionally. This may help the debugging. 112 additionally. This may help the debugging.
106 113
107 Since 2.6.30, this option also enables the hwptr check using 114 Since 2.6.30, this option can enable the hwptr check using
108 jiffies. This detects spontaneous invalid pointer callback 115 jiffies. This detects spontaneous invalid pointer callback
109 values, but can be lead to too much corrections for a (mostly 116 values, but can be lead to too much corrections for a (mostly
110 buggy) hardware that doesn't give smooth pointer updates. 117 buggy) hardware that doesn't give smooth pointer updates.
118 This feature is enabled via the bit 2.
111 119
112card*/pcm*/sub*/info 120card*/pcm*/sub*/info
113 The general information of this PCM sub-stream. 121 The general information of this PCM sub-stream.