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238 lines
6.6 KiB
238 lines
6.6 KiB
========================== |
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Proc Files of ALSA Drivers |
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========================== |
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Takashi Iwai <[email protected]> |
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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`` and |
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``CONFIG_SND_PCM_XRUN_DEBUG=y``. |
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This shows the status of xrun (= buffer overrun/xrun) and |
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invalid PCM position debug/check of ALSA PCM middle layer. |
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It takes an integer value, can be changed by writing to this |
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file, such as:: |
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# echo 5 > /proc/asound/card0/pcm0p/xrun_debug |
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The value consists of the following bit flags: |
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* bit 0 = Enable XRUN/jiffies debug messages |
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* bit 1 = Show stack trace at XRUN / jiffies check |
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* bit 2 = Enable additional jiffies check |
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When the bit 0 is set, the driver will show the messages to |
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kernel log when an xrun is detected. The debug message is |
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shown also when the invalid H/W pointer is detected at the |
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update of periods (usually called from the interrupt |
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handler). |
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When the bit 1 is set, the driver will show the stack trace |
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additionally. This may help the debugging. |
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Since 2.6.30, this option can enable the hwptr check using |
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jiffies. This detects spontaneous invalid pointer callback |
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values, but can be lead to too much corrections for a (mostly |
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buggy) hardware that doesn't give smooth pointer updates. |
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This feature is enabled via the bit 2. |
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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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``card*/pcm*/sub*/xrun_injection`` |
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Triggers an XRUN to the running stream when any value is |
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written to this proc file. Used for fault injection. |
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This entry is write-only. |
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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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:: |
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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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