Documentation/sound/alsa/Procfile.txt

   1                 Proc Files of ALSA Drivers
   2                 ==========================
   3                 Takashi Iwai <tiwai@suse.de>
   4
   5 General
   6 -------
   7
   8 ALSA has its own proc tree, /proc/asound.  Many useful information are
   9 found in this tree.  When you encounter a problem and need debugging,
  10 check the files listed in the following sections.
  11
  12 Each card has its subtree cardX, where X is from 0 to 7. The
  13 card-specific files are stored in the card* subdirectories.
  14
  15
  16 Global Information
  17 ------------------
  18
  19 cards
  20         Shows the list of currently configured ALSA drivers,
  21         index, the id string, short and long descriptions.
  22
  23 version
  24         Shows the version string and compile date.
  25
  26 modules
  27         Lists the module of each card
  28
  29 devices
  30         Lists the ALSA native device mappings.
  31
  32 meminfo
  33         Shows the status of allocated pages via ALSA drivers.
  34         Appears only when CONFIG_SND_DEBUG=y.
  35
  36 hwdep
  37         Lists the currently available hwdep devices in format of
  38         <card>-<device>: <name>
  39
  40 pcm
  41         Lists the currently available PCM devices in format of
  42         <card>-<device>: <id>: <name> : <sub-streams>
  43
  44 timer
  45         Lists the currently available timer devices
  46
  47
  48 oss/devices
  49         Lists the OSS device mappings.
  50
  51 oss/sndstat
  52         Provides the output compatible with /dev/sndstat.
  53         You can symlink this to /dev/sndstat.
  54
  55
  56 Card Specific Files
  57 -------------------
  58
  59 The card-specific files are found in /proc/asound/card* directories.
  60 Some drivers (e.g. cmipci) have their own proc entries for the
  61 register dump, etc (e.g. /proc/asound/card*/cmipci shows the register
  62 dump).  These files would be really helpful for debugging.
  63
  64 When PCM devices are available on this card, you can see directories
  65 like pcm0p or pcm1c.  They hold the PCM information for each PCM
  66 stream.  The number after 'pcm' is the PCM device number from 0, and
  67 the last 'p' or 'c' means playback or capture direction.  The files in
  68 this subtree is described later.
  69
  70 The status of MIDI I/O is found in midi* files.  It shows the device
  71 name and the received/transmitted bytes through the MIDI device.
  72
  73 When the card is equipped with AC97 codecs, there are codec97#*
  74 subdirectories (desribed later).
  75
  76 When the OSS mixer emulation is enabled (and the module is loaded),
  77 oss_mixer file appears here, too.  This shows the current mapping of
  78 OSS mixer elements to the ALSA control elements.  You can change the
  79 mapping by writing to this device.  Read OSS-Emulation.txt for
  80 details.
  81
  82
  83 PCM Proc Files
  84 --------------
  85
  86 card*/pcm*/info
  87         The general information of this PCM device: card #, device #,
  88         substreams, etc.
  89
  90 card*/pcm*/xrun_debug
  91         This file appears when CONFIG_SND_DEBUG=y.
  92         This shows the status of xrun (= buffer overrun/xrun) debug of
  93         ALSA PCM middle layer, as an integer from 0 to 2.  The value
  94         can be changed by writing to this file, such as
  95
  96                  # cat 2 > /proc/asound/card0/pcm0p/xrun_debug
  97
  98         When this value is greater than 0, the driver will show the
  99         messages to kernel log when an xrun is detected.  The debug
 100         message is shown also when the invalid H/W pointer is detected
 101         at the update of periods (usually called from the interrupt
 102         handler).
 103
 104         When this value is greater than 1, the driver will show the
 105         stack trace additionally.  This may help the debugging.
 106
 107 card*/pcm*/sub*/info
 108         The general information of this PCM sub-stream.
 109
 110 card*/pcm*/sub*/status
 111         The current status of this PCM sub-stream, elapsed time,
 112         H/W position, etc.
 113
 114 card*/pcm*/sub*/hw_params
 115         The hardware parameters set for this sub-stream.
 116
 117 card*/pcm*/sub*/sw_params
 118         The soft parameters set for this sub-stream.
 119
 120 card*/pcm*/sub*/prealloc
 121         The buffer pre-allocation information.
 122
 123
 124 AC97 Codec Information
 125 ----------------------
 126
 127 card*/codec97#*/ac97#?-?
 128         Shows the general information of this AC97 codec chip, such as
 129         name, capabilities, set up.
 130
 131 card*/codec97#0/ac97#?-?+regs
 132         Shows the AC97 register dump.  Useful for debugging.
 133
 134         When CONFIG_SND_DEBUG is enabled, you can write to this file for
 135         changing an AC97 register directly.  Pass two hex numbers.
 136         For example,
 137
 138         # echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs
 139
 140
 141 Sequencer Information
 142 ---------------------
 143
 144 seq/drivers
 145         Lists the currently available ALSA sequencer drivers.
 146
 147 seq/clients
 148         Shows the list of currently available sequencer clinets and
 149         ports.  The connection status and the running status are shown
 150         in this file, too.
 151
 152 seq/queues
 153         Lists the currently allocated/running sequener queues.
 154
 155 seq/timer
 156         Lists the currently allocated/running sequencer timers.
 157
 158 seq/oss
 159         Lists the OSS-compatible sequencer stuffs.
 160
 161
 162 Help For Debugging?
 163 -------------------
 164
 165 When the problem is related with PCM, first try to turn on xrun_debug
 166 mode.  This will give you the kernel messages when and where xrun
 167 happened.
 168
 169 If it's really a bug, report it with the following information
 170
 171   - the name of the driver/card, show in /proc/asound/cards
 172   - the reigster dump, if available (e.g. card*/cmipci)
 173
 174 when it's a PCM problem,
 175
 176   - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
 177     sub-stream directory
 178
 179 when it's a mixer problem,
 180
 181   - AC97 proc files, codec97#*/* files
 182
 183 for USB audio/midi,
 184
 185   - output of lsusb -v
 186   - stream* files in card directory
 187
 188
 189 The ALSA bug-tracking system is found at:
 190
 191     https://bugtrack.alsa-project.org/alsa-bug/