Based on kernel version 2.6.26. Page generated on 2008-07-16 21:13 EST.
1 Proc Files of ALSA Drivers 2 ========================== 3 Takashi Iwai <tiwai[AT]suse[DOT]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 (described 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 USB Audio Streams 142 ----------------- 143 144 card*/stream* 145 Shows the assignment and the current status of each audio stream 146 of the given card. This information is very useful for debugging. 147 148 149 HD-Audio Codecs 150 --------------- 151 152 card*/codec#* 153 Shows the general codec information and the attribute of each 154 widget node. 155 156 157 Sequencer Information 158 --------------------- 159 160 seq/drivers 161 Lists the currently available ALSA sequencer drivers. 162 163 seq/clients 164 Shows the list of currently available sequencer clients and 165 ports. The connection status and the running status are shown 166 in this file, too. 167 168 seq/queues 169 Lists the currently allocated/running sequencer queues. 170 171 seq/timer 172 Lists the currently allocated/running sequencer timers. 173 174 seq/oss 175 Lists the OSS-compatible sequencer stuffs. 176 177 178 Help For Debugging? 179 ------------------- 180 181 When the problem is related with PCM, first try to turn on xrun_debug 182 mode. This will give you the kernel messages when and where xrun 183 happened. 184 185 If it's really a bug, report it with the following information: 186 187 - the name of the driver/card, show in /proc/asound/cards 188 - the register dump, if available (e.g. card*/cmipci) 189 190 when it's a PCM problem, 191 192 - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM 193 sub-stream directory 194 195 when it's a mixer problem, 196 197 - AC97 proc files, codec97#*/* files 198 199 for USB audio/midi, 200 201 - output of lsusb -v 202 - stream* files in card directory 203 204 205 The ALSA bug-tracking system is found at: 206 207 https://bugtrack.alsa-project.org/alsa-bug/