1 ========================== 2 Proc Files of ALSA Drivers 3 ========================== 4 5 Takashi Iwai <tiwai@suse.de> 6 7 General 8 ======= 9 10 ALSA has its own proc tree, /proc/asound. Many useful information are 11 found in this tree. When you encounter a problem and need debugging, 12 check the files listed in the following sections. 13 14 Each card has its subtree cardX, where X is from 0 to 7. The 15 card-specific files are stored in the ``card*`` subdirectories. 16 17 18 Global Information 19 ================== 20 21 cards 22 Shows the list of currently configured ALSA drivers, 23 index, the id string, short and long descriptions. 24 25 version 26 Shows the version string and compile date. 27 28 modules 29 Lists the module of each card 30 31 devices 32 Lists the ALSA native device mappings. 33 34 meminfo 35 Shows the status of allocated pages via ALSA drivers. 36 Appears only when ``CONFIG_SND_DEBUG=y``. 37 38 hwdep 39 Lists the currently available hwdep devices in format of 40 ``<card>-<device>: <name>`` 41 42 pcm 43 Lists the currently available PCM devices in format of 44 ``<card>-<device>: <id>: <name> : <sub-streams>`` 45 46 timer 47 Lists the currently available timer devices 48 49 50 oss/devices 51 Lists the OSS device mappings. 52 53 oss/sndstat 54 Provides the output compatible with /dev/sndstat. 55 You can symlink this to /dev/sndstat. 56 57 58 Card Specific Files 59 =================== 60 61 The card-specific files are found in ``/proc/asound/card*`` directories. 62 Some drivers (e.g. cmipci) have their own proc entries for the 63 register dump, etc (e.g. ``/proc/asound/card*/cmipci`` shows the register 64 dump). These files would be really helpful for debugging. 65 66 When PCM devices are available on this card, you can see directories 67 like pcm0p or pcm1c. They hold the PCM information for each PCM 68 stream. The number after ``pcm`` is the PCM device number from 0, and 69 the last ``p`` or ``c`` means playback or capture direction. The files in 70 this subtree is described later. 71 72 The status of MIDI I/O is found in ``midi*`` files. It shows the device 73 name and the received/transmitted bytes through the MIDI device. 74 75 When the card is equipped with AC97 codecs, there are ``codec97#*`` 76 subdirectories (described later). 77 78 When the OSS mixer emulation is enabled (and the module is loaded), 79 oss_mixer file appears here, too. This shows the current mapping of 80 OSS mixer elements to the ALSA control elements. You can change the 81 mapping by writing to this device. Read OSS-Emulation.txt for 82 details. 83 84 85 PCM 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_SND_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. 143 144 AC97 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 161 162 163 USB 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. 169 170 171 HD-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. 187 188 189 Sequencer Information 190 ===================== 191 192 seq/drivers 193 Lists the currently available ALSA sequencer drivers. 194 195 seq/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. 199 200 seq/queues 201 Lists the currently allocated/running sequencer queues. 202 203 seq/timer 204 Lists the currently allocated/running sequencer timers. 205 206 seq/oss 207 Lists the OSS-compatible sequencer stuffs. 208 209 210 Help For Debugging? 211 =================== 212 213 When the problem is related with PCM, first try to turn on xrun_debug 214 mode. This will give you the kernel messages when and where xrun 215 happened. 216 217 If 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``) 221 222 when 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 226 227 when it's a mixer problem, 228 229 - AC97 proc files, ``codec97#*/*`` files 230 231 for USB audio/midi, 232 233 - output of ``lsusb -v`` 234 - ``stream*`` files in card directory 235 236 237 The ALSA bug-tracking system is found at: 238 https://bugtrack.alsa-project.org/alsa-bug/
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