1========================== 2Proc Files of ALSA Drivers 3========================== 4 5Takashi Iwai <tiwai@suse.de> 6 7General 8======= 9 10ALSA has its own proc tree, /proc/asound. Many useful information are 11found in this tree. When you encounter a problem and need debugging, 12check the files listed in the following sections. 13 14Each card has its subtree cardX, where X is from 0 to 7. The 15card-specific files are stored in the ``card*`` subdirectories. 16 17 18Global Information 19================== 20 21cards 22 Shows the list of currently configured ALSA drivers, 23 index, the id string, short and long descriptions. 24 25version 26 Shows the version string and compile date. 27 28modules 29 Lists the module of each card 30 31devices 32 Lists the ALSA native device mappings. 33 34meminfo 35 Shows the status of allocated pages via ALSA drivers. 36 Appears only when ``CONFIG_SND_DEBUG=y``. 37 38hwdep 39 Lists the currently available hwdep devices in format of 40 ``<card>-<device>: <name>`` 41 42pcm 43 Lists the currently available PCM devices in format of 44 ``<card>-<device>: <id>: <name> : <sub-streams>`` 45 46timer 47 Lists the currently available timer devices 48 49 50oss/devices 51 Lists the OSS device mappings. 52 53oss/sndstat 54 Provides the output compatible with /dev/sndstat. 55 You can symlink this to /dev/sndstat. 56 57 58Card Specific Files 59=================== 60 61The card-specific files are found in ``/proc/asound/card*`` directories. 62Some drivers (e.g. cmipci) have their own proc entries for the 63register dump, etc (e.g. ``/proc/asound/card*/cmipci`` shows the register 64dump). These files would be really helpful for debugging. 65 66When PCM devices are available on this card, you can see directories 67like pcm0p or pcm1c. They hold the PCM information for each PCM 68stream. The number after ``pcm`` is the PCM device number from 0, and 69the last ``p`` or ``c`` means playback or capture direction. The files in 70this subtree is described later. 71 72The status of MIDI I/O is found in ``midi*`` files. It shows the device 73name and the received/transmitted bytes through the MIDI device. 74 75When the card is equipped with AC97 codecs, there are ``codec97#*`` 76subdirectories (described later). 77 78When the OSS mixer emulation is enabled (and the module is loaded), 79oss_mixer file appears here, too. This shows the current mapping of 80OSS mixer elements to the ALSA control elements. You can change the 81mapping by writing to this device. Read OSS-Emulation.txt for 82details. 83 84 85PCM Proc Files 86============== 87 88``card*/pcm*/info`` 89 The general information of this PCM device: card #, device #, 90 substreams, etc. 91 92``card*/pcm*/xrun_debug`` 93 This file appears when ``CONFIG_SND_DEBUG=y`` and 94 ``CONFIG_PCM_XRUN_DEBUG=y``. 95 This shows the status of xrun (= buffer overrun/xrun) and 96 invalid PCM position debug/check of ALSA PCM middle layer. 97 It takes an integer value, can be changed by writing to this 98 file, such as:: 99 100 # echo 5 > /proc/asound/card0/pcm0p/xrun_debug 101 102 The value consists of the following bit flags: 103 104 * bit 0 = Enable XRUN/jiffies debug messages 105 * bit 1 = Show stack trace at XRUN / jiffies check 106 * bit 2 = Enable additional jiffies check 107 108 When the bit 0 is set, the driver will show the messages to 109 kernel log when an xrun is detected. The debug message is 110 shown also when the invalid H/W pointer is detected at the 111 update of periods (usually called from the interrupt 112 handler). 113 114 When the bit 1 is set, the driver will show the stack trace 115 additionally. This may help the debugging. 116 117 Since 2.6.30, this option can enable the hwptr check using 118 jiffies. This detects spontaneous invalid pointer callback 119 values, but can be lead to too much corrections for a (mostly 120 buggy) hardware that doesn't give smooth pointer updates. 121 This feature is enabled via the bit 2. 122 123``card*/pcm*/sub*/info`` 124 The general information of this PCM sub-stream. 125 126``card*/pcm*/sub*/status`` 127 The current status of this PCM sub-stream, elapsed time, 128 H/W position, etc. 129 130``card*/pcm*/sub*/hw_params`` 131 The hardware parameters set for this sub-stream. 132 133``card*/pcm*/sub*/sw_params`` 134 The soft parameters set for this sub-stream. 135 136``card*/pcm*/sub*/prealloc`` 137 The buffer pre-allocation information. 138 139``card*/pcm*/sub*/xrun_injection`` 140 Triggers an XRUN to the running stream when any value is 141 written to this proc file. Used for fault injection. 142 This entry is write-only. 143 144AC97 Codec Information 145====================== 146 147``card*/codec97#*/ac97#?-?`` 148 Shows the general information of this AC97 codec chip, such as 149 name, capabilities, set up. 150 151``card*/codec97#0/ac97#?-?+regs`` 152 Shows the AC97 register dump. Useful for debugging. 153 154 When CONFIG_SND_DEBUG is enabled, you can write to this file for 155 changing an AC97 register directly. Pass two hex numbers. 156 For example, 157 158:: 159 160 # echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs 161 162 163USB Audio Streams 164================= 165 166``card*/stream*`` 167 Shows the assignment and the current status of each audio stream 168 of the given card. This information is very useful for debugging. 169 170 171HD-Audio Codecs 172=============== 173 174``card*/codec#*`` 175 Shows the general codec information and the attribute of each 176 widget node. 177 178``card*/eld#*`` 179 Available for HDMI or DisplayPort interfaces. 180 Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink, 181 and describes its audio capabilities and configurations. 182 183 Some ELD fields may be modified by doing ``echo name hex_value > eld#*``. 184 Only do this if you are sure the HDMI sink provided value is wrong. 185 And if that makes your HDMI audio work, please report to us so that we 186 can fix it in future kernel releases. 187 188 189Sequencer Information 190===================== 191 192seq/drivers 193 Lists the currently available ALSA sequencer drivers. 194 195seq/clients 196 Shows the list of currently available sequencer clients and 197 ports. The connection status and the running status are shown 198 in this file, too. 199 200seq/queues 201 Lists the currently allocated/running sequencer queues. 202 203seq/timer 204 Lists the currently allocated/running sequencer timers. 205 206seq/oss 207 Lists the OSS-compatible sequencer stuffs. 208 209 210Help For Debugging? 211=================== 212 213When the problem is related with PCM, first try to turn on xrun_debug 214mode. This will give you the kernel messages when and where xrun 215happened. 216 217If it's really a bug, report it with the following information: 218 219- the name of the driver/card, show in ``/proc/asound/cards`` 220- the register dump, if available (e.g. ``card*/cmipci``) 221 222when it's a PCM problem, 223 224- set-up of PCM, shown in hw_parms, sw_params, and status in the PCM 225 sub-stream directory 226 227when it's a mixer problem, 228 229- AC97 proc files, ``codec97#*/*`` files 230 231for USB audio/midi, 232 233- output of ``lsusb -v`` 234- ``stream*`` files in card directory 235 236 237The ALSA bug-tracking system is found at: 238https://bugtrack.alsa-project.org/alsa-bug/ 239