| ========================== |
| 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 (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 |
| |
| 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. |
| |
| ``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. |
| |
| ``card*/pcm*/sub*/xrun_injection`` |
| Triggers an XRUN to the running stream when any value is |
| written to this proc file. Used for fault injection. |
| This entry is write-only. |
| |
| 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/ |
