Based on kernel version 4.9. Page generated on 2016-12-21 14:37 EST.
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 (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 104 105 When the bit 0 is set, the driver will show the messages to 106 kernel log when an xrun is detected. The debug message is 107 shown also when the invalid H/W pointer is detected at the 108 update of periods (usually called from the interrupt 109 handler). 110 111 When the bit 1 is set, the driver will show the stack trace 112 additionally. This may help the debugging. 113 114 Since 2.6.30, this option can enable the hwptr check using 115 jiffies. This detects spontaneous invalid pointer callback 116 values, but can be lead to too much corrections for a (mostly 117 buggy) hardware that doesn't give smooth pointer updates. 118 This feature is enabled via the bit 2. 119 120 card*/pcm*/sub*/info 121 The general information of this PCM sub-stream. 122 123 card*/pcm*/sub*/status 124 The current status of this PCM sub-stream, elapsed time, 125 H/W position, etc. 126 127 card*/pcm*/sub*/hw_params 128 The hardware parameters set for this sub-stream. 129 130 card*/pcm*/sub*/sw_params 131 The soft parameters set for this sub-stream. 132 133 card*/pcm*/sub*/prealloc 134 The buffer pre-allocation information. 135 136 card*/pcm*/sub*/xrun_injection 137 Triggers an XRUN to the running stream when any value is 138 written to this proc file. Used for fault injection. 139 This entry is write-only. 140 141 AC97 Codec Information 142 ---------------------- 143 144 card*/codec97#*/ac97#?-? 145 Shows the general information of this AC97 codec chip, such as 146 name, capabilities, set up. 147 148 card*/codec97#0/ac97#?-?+regs 149 Shows the AC97 register dump. Useful for debugging. 150 151 When CONFIG_SND_DEBUG is enabled, you can write to this file for 152 changing an AC97 register directly. Pass two hex numbers. 153 For example, 154 155 # echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs 156 157 158 USB Audio Streams 159 ----------------- 160 161 card*/stream* 162 Shows the assignment and the current status of each audio stream 163 of the given card. This information is very useful for debugging. 164 165 166 HD-Audio Codecs 167 --------------- 168 169 card*/codec#* 170 Shows the general codec information and the attribute of each 171 widget node. 172 173 card*/eld#* 174 Available for HDMI or DisplayPort interfaces. 175 Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink, 176 and describes its audio capabilities and configurations. 177 178 Some ELD fields may be modified by doing `echo name hex_value > eld#*`. 179 Only do this if you are sure the HDMI sink provided value is wrong. 180 And if that makes your HDMI audio work, please report to us so that we 181 can fix it in future kernel releases. 182 183 184 Sequencer Information 185 --------------------- 186 187 seq/drivers 188 Lists the currently available ALSA sequencer drivers. 189 190 seq/clients 191 Shows the list of currently available sequencer clients and 192 ports. The connection status and the running status are shown 193 in this file, too. 194 195 seq/queues 196 Lists the currently allocated/running sequencer queues. 197 198 seq/timer 199 Lists the currently allocated/running sequencer timers. 200 201 seq/oss 202 Lists the OSS-compatible sequencer stuffs. 203 204 205 Help For Debugging? 206 ------------------- 207 208 When the problem is related with PCM, first try to turn on xrun_debug 209 mode. This will give you the kernel messages when and where xrun 210 happened. 211 212 If it's really a bug, report it with the following information: 213 214 - the name of the driver/card, show in /proc/asound/cards 215 - the register dump, if available (e.g. card*/cmipci) 216 217 when it's a PCM problem, 218 219 - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM 220 sub-stream directory 221 222 when it's a mixer problem, 223 224 - AC97 proc files, codec97#*/* files 225 226 for USB audio/midi, 227 228 - output of lsusb -v 229 - stream* files in card directory 230 231 232 The ALSA bug-tracking system is found at: 233 234 https://bugtrack.alsa-project.org/alsa-bug/