| 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. | |
| This shows the status of xrun (= buffer overrun/xrun) debug of | |
| ALSA PCM middle layer, as an integer from 0 to 2. The value | |
| can be changed by writing to this file, such as | |
| # cat 2 > /proc/asound/card0/pcm0p/xrun_debug | |
| When this value is greater than 0, 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 this value is greater than 1, the driver will show the | |
| stack trace additionally. This may help the debugging. | |
| 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. | |
| 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/ |