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Describe what ELD proc interface provides and how to fix incorrect values. Signed-off-by: Wu Fengguang <wfg@linux.intel.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
218 lines
5.8 KiB
Plaintext
218 lines
5.8 KiB
Plaintext
Proc Files of ALSA Drivers
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==========================
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Takashi Iwai <tiwai@suse.de>
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General
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-------
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ALSA has its own proc tree, /proc/asound. Many useful information are
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found in this tree. When you encounter a problem and need debugging,
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check the files listed in the following sections.
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Each card has its subtree cardX, where X is from 0 to 7. The
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card-specific files are stored in the card* subdirectories.
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Global Information
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------------------
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cards
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Shows the list of currently configured ALSA drivers,
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index, the id string, short and long descriptions.
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version
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Shows the version string and compile date.
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modules
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Lists the module of each card
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devices
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Lists the ALSA native device mappings.
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meminfo
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Shows the status of allocated pages via ALSA drivers.
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Appears only when CONFIG_SND_DEBUG=y.
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hwdep
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Lists the currently available hwdep devices in format of
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<card>-<device>: <name>
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pcm
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Lists the currently available PCM devices in format of
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<card>-<device>: <id>: <name> : <sub-streams>
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timer
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Lists the currently available timer devices
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oss/devices
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Lists the OSS device mappings.
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oss/sndstat
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Provides the output compatible with /dev/sndstat.
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You can symlink this to /dev/sndstat.
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Card Specific Files
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-------------------
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The card-specific files are found in /proc/asound/card* directories.
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Some drivers (e.g. cmipci) have their own proc entries for the
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register dump, etc (e.g. /proc/asound/card*/cmipci shows the register
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dump). These files would be really helpful for debugging.
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When PCM devices are available on this card, you can see directories
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like pcm0p or pcm1c. They hold the PCM information for each PCM
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stream. The number after 'pcm' is the PCM device number from 0, and
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the last 'p' or 'c' means playback or capture direction. The files in
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this subtree is described later.
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The status of MIDI I/O is found in midi* files. It shows the device
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name and the received/transmitted bytes through the MIDI device.
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When the card is equipped with AC97 codecs, there are codec97#*
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subdirectories (described later).
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When the OSS mixer emulation is enabled (and the module is loaded),
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oss_mixer file appears here, too. This shows the current mapping of
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OSS mixer elements to the ALSA control elements. You can change the
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mapping by writing to this device. Read OSS-Emulation.txt for
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details.
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PCM Proc Files
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--------------
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card*/pcm*/info
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The general information of this PCM device: card #, device #,
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substreams, etc.
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card*/pcm*/xrun_debug
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This file appears when CONFIG_SND_DEBUG=y.
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This shows the status of xrun (= buffer overrun/xrun) debug of
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ALSA PCM middle layer, as an integer from 0 to 2. The value
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can be changed by writing to this file, such as
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# cat 2 > /proc/asound/card0/pcm0p/xrun_debug
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When this value is greater than 0, the driver will show the
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messages to kernel log when an xrun is detected. The debug
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message is shown also when the invalid H/W pointer is detected
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at the update of periods (usually called from the interrupt
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handler).
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When this value is greater than 1, the driver will show the
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stack trace additionally. This may help the debugging.
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card*/pcm*/sub*/info
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The general information of this PCM sub-stream.
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card*/pcm*/sub*/status
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The current status of this PCM sub-stream, elapsed time,
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H/W position, etc.
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card*/pcm*/sub*/hw_params
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The hardware parameters set for this sub-stream.
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card*/pcm*/sub*/sw_params
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The soft parameters set for this sub-stream.
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card*/pcm*/sub*/prealloc
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The buffer pre-allocation information.
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AC97 Codec Information
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----------------------
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card*/codec97#*/ac97#?-?
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Shows the general information of this AC97 codec chip, such as
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name, capabilities, set up.
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card*/codec97#0/ac97#?-?+regs
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Shows the AC97 register dump. Useful for debugging.
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When CONFIG_SND_DEBUG is enabled, you can write to this file for
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changing an AC97 register directly. Pass two hex numbers.
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For example,
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# echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs
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USB Audio Streams
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-----------------
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card*/stream*
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Shows the assignment and the current status of each audio stream
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of the given card. This information is very useful for debugging.
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HD-Audio Codecs
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---------------
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card*/codec#*
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Shows the general codec information and the attribute of each
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widget node.
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card*/eld#*
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Available for HDMI or DisplayPort interfaces.
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Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink,
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and describes its audio capabilities and configurations.
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Some ELD fields may be modified by doing `echo name hex_value > eld#*`.
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Only do this if you are sure the HDMI sink provided value is wrong.
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And if that makes your HDMI audio work, please report to us so that we
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can fix it in future kernel releases.
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Sequencer Information
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---------------------
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seq/drivers
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Lists the currently available ALSA sequencer drivers.
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seq/clients
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Shows the list of currently available sequencer clients and
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ports. The connection status and the running status are shown
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in this file, too.
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seq/queues
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Lists the currently allocated/running sequencer queues.
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seq/timer
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Lists the currently allocated/running sequencer timers.
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seq/oss
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Lists the OSS-compatible sequencer stuffs.
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Help For Debugging?
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-------------------
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When the problem is related with PCM, first try to turn on xrun_debug
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mode. This will give you the kernel messages when and where xrun
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happened.
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If it's really a bug, report it with the following information:
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- the name of the driver/card, show in /proc/asound/cards
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- the register dump, if available (e.g. card*/cmipci)
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when it's a PCM problem,
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- set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
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sub-stream directory
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when it's a mixer problem,
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- AC97 proc files, codec97#*/* files
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for USB audio/midi,
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- output of lsusb -v
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- stream* files in card directory
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The ALSA bug-tracking system is found at:
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https://bugtrack.alsa-project.org/alsa-bug/
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