Documentation / sound / alsa / Procfile.txt

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Based on kernel version 2.6.33. Page generated on 2010-02-24 15:37 EST.

			Proc Files of ALSA Drivers
			==========================
			Takashi Iwai <tiwai[AT]suse[DOT]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 (described 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 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
	
			 # echo 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
		  bit 3 = Log hwptr update at each period interrupt
		  bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr()
	
		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 the bit 1 is set, the driver will show the stack trace
		additionally.  This may help the debugging.
	
		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.
	
		Bits 3 and 4 are for logging the hwptr records.  Note that
		these will give flood of kernel messages.
	
	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+regs
	
	
	USB Audio Streams
	-----------------
	
	card*/stream*
		Shows the assignment and the current status of each audio stream
		of the given card.  This information is very useful for debugging.
	
	
	HD-Audio Codecs
	---------------
	
	card*/codec#*
		Shows the general codec information and the attribute of each
		widget node.
	
	card*/eld#*
		Available for HDMI or DisplayPort interfaces.
		Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink,
		and describes its audio capabilities and configurations.
	
		Some ELD fields may be modified by doing `echo name hex_value > eld#*`.
		Only do this if you are sure the HDMI sink provided value is wrong.
		And if that makes your HDMI audio work, please report to us so that we
		can fix it in future kernel releases.
	
	
	Sequencer Information
	---------------------
	
	seq/drivers
		Lists the currently available ALSA sequencer drivers.
	
	seq/clients
		Shows the list of currently available sequencer clients and
		ports.  The connection status and the running status are shown
		in this file, too.
	
	seq/queues
		Lists the currently allocated/running sequencer 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 register 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/

• [ alsa ]
• ALSA-Configuration.txt
• Audigy-mixer.txt
• Audiophile-Usb.txt
• Bt87x.txt
• CMIPCI.txt
• ControlNames.txt
• emu10k1-jack.txt
• HD-Audio-Models.txt
• HD-Audio.txt
• hda_codec.txt
• hdspm.txt
• Joystick.txt
• MIXART.txt
• OSS-Emulation.txt
• powersave.txt
• Procfile.txt
• README.maya44
• SB-Live-mixer.txt
• seq_oss.html
• serial-u16550.txt
• [ soc ]
• VIA82xx-mixer.txt
•