Proc Files of ALSA Drivers		==========================		Takashi Iwai <tiwai@suse.de>General-------ALSA has its own proc tree, /proc/asound.  Many useful information arefound 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. Thecard-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 carddevices	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 devicesoss/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 theregister dump, etc (e.g. /proc/asound/card*/cmipci shows the registerdump).  These files would be really helpful for debugging.When PCM devices are available on this card, you can see directorieslike pcm0p or pcm1c.  They hold the PCM information for each PCMstream.  The number after 'pcm' is the PCM device number from 0, andthe last 'p' or 'c' means playback or capture direction.  The files inthis subtree is described later.The status of MIDI I/O is found in midi* files.  It shows the devicename 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 ofOSS mixer elements to the ALSA control elements.  You can change themapping by writing to this device.  Read OSS-Emulation.txt fordetails.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		 # 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	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.	When CONFIG_SND_DEBUG is enabled, you can write to this file for	changing an AC97 register directly.  Pass two hex numbers.	For example,	# echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regsSequencer 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_debugmode.  This will give you the kernel messages when and where xrunhappened.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 directorywhen it's a mixer problem,  - AC97 proc files, codec97#*/* filesfor USB audio/midi,  - output of lsusb -v  - stream* files in card directoryThe ALSA bug-tracking system is found at:    https://bugtrack.alsa-project.org/alsa-bug/