Based on kernel version 2.6.33. Page generated on 2010-02-24 15:37 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 and 92 CONFIG_PCM_XRUN_DEBUG=y. 93 This shows the status of xrun (= buffer overrun/xrun) and 94 invalid PCM position debug/check of ALSA PCM middle layer. 95 It takes an integer value, can be changed by writing to this 96 file, such as 97 98 # echo 5 > /proc/asound/card0/pcm0p/xrun_debug 99 100 The value consists of the following bit flags: 101 bit 0 = Enable XRUN/jiffies debug messages 102 bit 1 = Show stack trace at XRUN / jiffies check 103 bit 2 = Enable additional jiffies check 104 bit 3 = Log hwptr update at each period interrupt 105 bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr() 106 107 When the bit 0 is set, the driver will show the messages to 108 kernel log when an xrun is detected. The debug message is 109 shown also when the invalid H/W pointer is detected at the 110 update of periods (usually called from the interrupt 111 handler). 112 113 When the bit 1 is set, the driver will show the stack trace 114 additionally. This may help the debugging. 115 116 Since 2.6.30, this option can enable the hwptr check using 117 jiffies. This detects spontaneous invalid pointer callback 118 values, but can be lead to too much corrections for a (mostly 119 buggy) hardware that doesn't give smooth pointer updates. 120 This feature is enabled via the bit 2. 121 122 Bits 3 and 4 are for logging the hwptr records. Note that 123 these will give flood of kernel messages. 124 125 card*/pcm*/sub*/info 126 The general information of this PCM sub-stream. 127 128 card*/pcm*/sub*/status 129 The current status of this PCM sub-stream, elapsed time, 130 H/W position, etc. 131 132 card*/pcm*/sub*/hw_params 133 The hardware parameters set for this sub-stream. 134 135 card*/pcm*/sub*/sw_params 136 The soft parameters set for this sub-stream. 137 138 card*/pcm*/sub*/prealloc 139 The buffer pre-allocation information. 140 141 142 AC97 Codec Information 143 ---------------------- 144 145 card*/codec97#*/ac97#?-? 146 Shows the general information of this AC97 codec chip, such as 147 name, capabilities, set up. 148 149 card*/codec97#0/ac97#?-?+regs 150 Shows the AC97 register dump. Useful for debugging. 151 152 When CONFIG_SND_DEBUG is enabled, you can write to this file for 153 changing an AC97 register directly. Pass two hex numbers. 154 For example, 155 156 # echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs 157 158 159 USB Audio Streams 160 ----------------- 161 162 card*/stream* 163 Shows the assignment and the current status of each audio stream 164 of the given card. This information is very useful for debugging. 165 166 167 HD-Audio Codecs 168 --------------- 169 170 card*/codec#* 171 Shows the general codec information and the attribute of each 172 widget node. 173 174 card*/eld#* 175 Available for HDMI or DisplayPort interfaces. 176 Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink, 177 and describes its audio capabilities and configurations. 178 179 Some ELD fields may be modified by doing `echo name hex_value > eld#*`. 180 Only do this if you are sure the HDMI sink provided value is wrong. 181 And if that makes your HDMI audio work, please report to us so that we 182 can fix it in future kernel releases. 183 184 185 Sequencer Information 186 --------------------- 187 188 seq/drivers 189 Lists the currently available ALSA sequencer drivers. 190 191 seq/clients 192 Shows the list of currently available sequencer clients and 193 ports. The connection status and the running status are shown 194 in this file, too. 195 196 seq/queues 197 Lists the currently allocated/running sequencer queues. 198 199 seq/timer 200 Lists the currently allocated/running sequencer timers. 201 202 seq/oss 203 Lists the OSS-compatible sequencer stuffs. 204 205 206 Help For Debugging? 207 ------------------- 208 209 When the problem is related with PCM, first try to turn on xrun_debug 210 mode. This will give you the kernel messages when and where xrun 211 happened. 212 213 If it's really a bug, report it with the following information: 214 215 - the name of the driver/card, show in /proc/asound/cards 216 - the register dump, if available (e.g. card*/cmipci) 217 218 when it's a PCM problem, 219 220 - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM 221 sub-stream directory 222 223 when it's a mixer problem, 224 225 - AC97 proc files, codec97#*/* files 226 227 for USB audio/midi, 228 229 - output of lsusb -v 230 - stream* files in card directory 231 232 233 The ALSA bug-tracking system is found at: 234 235 https://bugtrack.alsa-project.org/alsa-bug/