Procfile.txt

 Proc Files of ALSA Drivers
 
 Takashi Iwai <tiwai@suse.de>
 
 General
 -------
 
 ALSA has its own proc tree, /proc/asound.  Many useful information are
 found in this tree.  When you encounter a problem and need debugging,
 check the files listed in the following sections.
 
 Each card has its subtree cardX, where X is from 0 to 7. The
 card-specific files are stored in the card* subdirectories.
 
 
 Global Information
 ------------------
 
 cards
 	Shows the list of currently configured ALSA drivers,
 	index, the id string, short and long descriptions.
 
 version
 	Shows the version string and compile date.
 
 modules
 	Lists the module of each card
 
 devices
 	Lists the ALSA native device mappings.
 
 meminfo
 	Shows the status of allocated pages via ALSA drivers.
 	Appears only when CONFIG_SND_DEBUG=y.
 
 hwdep
 	Lists the currently available hwdep devices in format of
 	<card>-<device>: <name>
 
 pcm
 	Lists the currently available PCM devices in format of
 	<card>-<device>: <id>: <name> : <sub-streams>
 
 timer
 	Lists the currently available timer devices
 
 
 oss/devices
 	Lists the OSS device mappings.
 
 oss/sndstat
 	Provides the output compatible with /dev/sndstat.
 	You can symlink this to /dev/sndstat.
 
 
 Card Specific Files
 -------------------
 
 The card-specific files are found in /proc/asound/card* directories.
 Some drivers (e.g. cmipci) have their own proc entries for the
 register dump, etc (e.g. /proc/asound/card*/cmipci shows the register
 dump).  These files would be really helpful for debugging.
 
 When PCM devices are available on this card, you can see directories
 like pcm0p or pcm1c.  They hold the PCM information for each PCM
 stream.  The number after 'pcm' is the PCM device number from 0, and
 the last 'p' or 'c' means playback or capture direction.  The files in
 this subtree is described later.
 
 The status of MIDI I/O is found in midi* files.  It shows the device
 name and the received/transmitted bytes through the MIDI device.
 
 When the card is equipped with AC97 codecs, there are codec97#*
 subdirectories (desribed later).
 
 When the OSS mixer emulation is enabled (and the module is loaded),
 oss_mixer file appears here, too.  This shows the current mapping of
 OSS mixer elements to the ALSA control elements.  You can change the
 mapping by writing to this device.  Read OSS-Emulation.txt for
 details.
 
 
 PCM Proc Files
 --------------
 
 card*/pcm*/info
 	The general information of this PCM device: card #, device #,
 	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
 
 		 # echo 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
 	handler).
 
 	When this value is greater than 1, the driver will show the
 	stack trace additionally.  This may help the debugging.
 
 card*/pcm*/sub*/info
 	The general information of this PCM sub-stream.
 
 card*/pcm*/sub*/status
 	The current status of this PCM sub-stream, elapsed time,
 	H/W position, etc.
 
 card*/pcm*/sub*/hw_params
 	The hardware parameters set for this sub-stream.
 
 card*/pcm*/sub*/sw_params
 	The soft parameters set for this sub-stream.
 
 card*/pcm*/sub*/prealloc
 	The buffer pre-allocation information.
 
 
 AC97 Codec Information
 ----------------------
 
 card*/codec97#*/ac97#?-?
 	Shows the general information of this AC97 codec chip, such as
 	name, capabilities, set up.
 
 card*/codec97#0/ac97#?-?+regs
 	Shows the AC97 register dump.  Useful for debugging.
 
 
 Sequencer Information
 ---------------------
 
 seq/drivers
 	Lists the currently available ALSA sequencer drivers.
 
 seq/clients
 	Shows the list of currently available sequencer clinets and
 	ports.  The connection status and the running status are shown
 	in this file, too.
 
 seq/queues
 	Lists the currently allocated/running sequener queues.
 
 seq/timer
 	Lists the currently allocated/running sequencer timers.
 
 seq/oss
 	Lists the OSS-compatible sequencer stuffs.
 
 
 Help For Debugging?
 -------------------
 
 When the problem is related with PCM, first try to turn on xrun_debug
 mode.  This will give you the kernel messages when and where xrun
 happened.
 
 If it's really a bug, report it with the following information
 
   - the name of the driver/card, show in /proc/asound/cards
   - the reigster dump, if available (e.g. card*/cmipci)
 
 when it's a PCM problem,
 
   - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
     sub-stream directory
 
 when it's a mixer problem,
 
   - AC97 proc files, codec97#*/* files
 
 for USB audio/midi,
 
   - output of lsusb -v
   - stream* files in card directory
 
 
 The ALSA bug-tracking system is found at:
 
     https://bugtrack.alsa-project.org/alsa-bug/