Documentation/sound/designs/procfile.rst

Source file repositories/reference/linux-study-clean/Documentation/sound/designs/procfile.rst

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Documentation/sound/designs/procfile.rst
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Support Tooling And Documentation: documentation
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==========================
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.

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