1 Proc Files of ALSA Drivers
2 ==========================
3 Takashi Iwai <tiwai@suse.de>
8 ALSA has its own proc tree, /proc/asound. Many useful information are
9 found in this tree. When you encounter a problem and need debugging,
10 check the files listed in the following sections.
12 Each card has its subtree cardX, where X is from 0 to 7. The
13 card-specific files are stored in the card* subdirectories.
20 Shows the list of currently configured ALSA drivers,
21 index, the id string, short and long descriptions.
24 Shows the version string and compile date.
27 Lists the module of each card
30 Lists the ALSA native device mappings.
33 Shows the status of allocated pages via ALSA drivers.
34 Appears only when CONFIG_SND_DEBUG=y.
37 Lists the currently available hwdep devices in format of
38 <card>-<device>: <name>
41 Lists the currently available PCM devices in format of
42 <card>-<device>: <id>: <name> : <sub-streams>
45 Lists the currently available timer devices
49 Lists the OSS device mappings.
52 Provides the output compatible with /dev/sndstat.
53 You can symlink this to /dev/sndstat.
59 The card-specific files are found in /proc/asound/card* directories.
60 Some drivers (e.g. cmipci) have their own proc entries for the
61 register dump, etc (e.g. /proc/asound/card*/cmipci shows the register
62 dump). These files would be really helpful for debugging.
64 When PCM devices are available on this card, you can see directories
65 like pcm0p or pcm1c. They hold the PCM information for each PCM
66 stream. The number after 'pcm' is the PCM device number from 0, and
67 the last 'p' or 'c' means playback or capture direction. The files in
68 this subtree is described later.
70 The status of MIDI I/O is found in midi* files. It shows the device
71 name and the received/transmitted bytes through the MIDI device.
73 When the card is equipped with AC97 codecs, there are codec97#*
74 subdirectories (desribed later).
76 When the OSS mixer emulation is enabled (and the module is loaded),
77 oss_mixer file appears here, too. This shows the current mapping of
78 OSS mixer elements to the ALSA control elements. You can change the
79 mapping by writing to this device. Read OSS-Emulation.txt for
87 The general information of this PCM device: card #, device #,
91 This file appears when CONFIG_SND_DEBUG=y.
92 This shows the status of xrun (= buffer overrun/xrun) debug of
93 ALSA PCM middle layer, as an integer from 0 to 2. The value
94 can be changed by writing to this file, such as
96 # cat 2 > /proc/asound/card0/pcm0p/xrun_debug
98 When this value is greater than 0, the driver will show the
99 messages to kernel log when an xrun is detected. The debug
100 message is shown also when the invalid H/W pointer is detected
101 at the update of periods (usually called from the interrupt
104 When this value is greater than 1, the driver will show the
105 stack trace additionally. This may help the debugging.
108 The general information of this PCM sub-stream.
110 card*/pcm*/sub*/status
111 The current status of this PCM sub-stream, elapsed time,
114 card*/pcm*/sub*/hw_params
115 The hardware parameters set for this sub-stream.
117 card*/pcm*/sub*/sw_params
118 The soft parameters set for this sub-stream.
120 card*/pcm*/sub*/prealloc
121 The buffer pre-allocation information.
124 AC97 Codec Information
125 ----------------------
127 card*/codec97#*/ac97#?-?
128 Shows the general information of this AC97 codec chip, such as
129 name, capabilities, set up.
131 card*/codec97#0/ac97#?-?+regs
132 Shows the AC97 register dump. Useful for debugging.
135 Sequencer Information
136 ---------------------
139 Lists the currently available ALSA sequencer drivers.
142 Shows the list of currently available sequencer clinets and
143 ports. The connection status and the running status are shown
147 Lists the currently allocated/running sequener queues.
150 Lists the currently allocated/running sequencer timers.
153 Lists the OSS-compatible sequencer stuffs.
159 When the problem is related with PCM, first try to turn on xrun_debug
160 mode. This will give you the kernel messages when and where xrun
163 If it's really a bug, report it with the following information
165 - the name of the driver/card, show in /proc/asound/cards
166 - the reigster dump, if available (e.g. card*/cmipci)
168 when it's a PCM problem,
170 - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
173 when it's a mixer problem,
175 - AC97 proc files, codec97#*/* files
180 - stream* files in card directory
183 The ALSA bug-tracking system is found at:
185 https://bugtrack.alsa-project.org/alsa-bug/