| ========================== | |
| 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_SND_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/ |