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Linus Torvalds1da177e2005-04-16 15:20:36 -07001 Proc Files of ALSA Drivers
2 ==========================
3 Takashi Iwai <tiwai@suse.de>
4
5General
6-------
7
8ALSA has its own proc tree, /proc/asound. Many useful information are
9found in this tree. When you encounter a problem and need debugging,
10check the files listed in the following sections.
11
12Each card has its subtree cardX, where X is from 0 to 7. The
13card-specific files are stored in the card* subdirectories.
14
15
16Global Information
17------------------
18
19cards
20 Shows the list of currently configured ALSA drivers,
21 index, the id string, short and long descriptions.
22
23version
24 Shows the version string and compile date.
25
26modules
27 Lists the module of each card
28
29devices
30 Lists the ALSA native device mappings.
31
32meminfo
33 Shows the status of allocated pages via ALSA drivers.
34 Appears only when CONFIG_SND_DEBUG=y.
35
36hwdep
37 Lists the currently available hwdep devices in format of
38 <card>-<device>: <name>
39
40pcm
41 Lists the currently available PCM devices in format of
42 <card>-<device>: <id>: <name> : <sub-streams>
43
44timer
45 Lists the currently available timer devices
46
47
48oss/devices
49 Lists the OSS device mappings.
50
51oss/sndstat
52 Provides the output compatible with /dev/sndstat.
53 You can symlink this to /dev/sndstat.
54
55
56Card Specific Files
57-------------------
58
59The card-specific files are found in /proc/asound/card* directories.
60Some drivers (e.g. cmipci) have their own proc entries for the
61register dump, etc (e.g. /proc/asound/card*/cmipci shows the register
62dump). These files would be really helpful for debugging.
63
64When PCM devices are available on this card, you can see directories
65like pcm0p or pcm1c. They hold the PCM information for each PCM
66stream. The number after 'pcm' is the PCM device number from 0, and
67the last 'p' or 'c' means playback or capture direction. The files in
68this subtree is described later.
69
70The status of MIDI I/O is found in midi* files. It shows the device
71name and the received/transmitted bytes through the MIDI device.
72
73When the card is equipped with AC97 codecs, there are codec97#*
Matt LaPlantefff92892006-10-03 22:47:42 +020074subdirectories (described later).
Linus Torvalds1da177e2005-04-16 15:20:36 -070075
76When the OSS mixer emulation is enabled (and the module is loaded),
77oss_mixer file appears here, too. This shows the current mapping of
78OSS mixer elements to the ALSA control elements. You can change the
79mapping by writing to this device. Read OSS-Emulation.txt for
80details.
81
82
83PCM Proc Files
84--------------
85
86card*/pcm*/info
87 The general information of this PCM device: card #, device #,
88 substreams, etc.
89
90card*/pcm*/xrun_debug
Takashi Iwai4f64e152009-06-11 16:14:11 +020091 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070097
Takashi Iwai4f64e152009-06-11 16:14:11 +020098 # cat 5 > /proc/asound/card0/pcm0p/xrun_debug
Linus Torvalds1da177e2005-04-16 15:20:36 -070099
Takashi Iwai4f64e152009-06-11 16:14:11 +0200100 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
Takashi Iwaicedb8112009-07-23 11:04:13 +0200104 bit 3 = Log hwptr update at each period interrupt
105 bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr()
Takashi Iwai4f64e152009-06-11 16:14:11 +0200106
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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 handler).
112
Takashi Iwai4f64e152009-06-11 16:14:11 +0200113 When the bit 1 is set, the driver will show the stack trace
114 additionally. This may help the debugging.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115
Takashi Iwai4f64e152009-06-11 16:14:11 +0200116 Since 2.6.30, this option can enable the hwptr check using
Takashi Iwaic87d9732009-05-27 10:53:33 +0200117 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.
Takashi Iwai4f64e152009-06-11 16:14:11 +0200120 This feature is enabled via the bit 2.
Takashi Iwaic87d9732009-05-27 10:53:33 +0200121
Takashi Iwaicedb8112009-07-23 11:04:13 +0200122 Bits 3 and 4 are for logging the hwptr records. Note that
123 these will give flood of kernel messages.
124
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125card*/pcm*/sub*/info
126 The general information of this PCM sub-stream.
127
128card*/pcm*/sub*/status
129 The current status of this PCM sub-stream, elapsed time,
130 H/W position, etc.
131
132card*/pcm*/sub*/hw_params
133 The hardware parameters set for this sub-stream.
134
135card*/pcm*/sub*/sw_params
136 The soft parameters set for this sub-stream.
137
138card*/pcm*/sub*/prealloc
139 The buffer pre-allocation information.
140
141
142AC97 Codec Information
143----------------------
144
145card*/codec97#*/ac97#?-?
146 Shows the general information of this AC97 codec chip, such as
147 name, capabilities, set up.
148
149card*/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
Takashi Iwai59de6412005-11-17 11:05:34 +0100159USB Audio Streams
160-----------------
161
162card*/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
167HD-Audio Codecs
168---------------
169
170card*/codec#*
171 Shows the general codec information and the attribute of each
172 widget node.
173
Wu Fengguanga5fcf892008-11-22 09:40:55 +0800174card*/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
Takashi Iwai59de6412005-11-17 11:05:34 +0100184
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185Sequencer Information
186---------------------
187
188seq/drivers
189 Lists the currently available ALSA sequencer drivers.
190
191seq/clients
Matt LaPlante53cb4722006-10-03 22:55:17 +0200192 Shows the list of currently available sequencer clients and
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 ports. The connection status and the running status are shown
194 in this file, too.
195
196seq/queues
Matt LaPlante53cb4722006-10-03 22:55:17 +0200197 Lists the currently allocated/running sequencer queues.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
199seq/timer
200 Lists the currently allocated/running sequencer timers.
201
202seq/oss
203 Lists the OSS-compatible sequencer stuffs.
204
205
206Help For Debugging?
207-------------------
208
209When the problem is related with PCM, first try to turn on xrun_debug
210mode. This will give you the kernel messages when and where xrun
211happened.
212
Matt LaPlanted6bc8ac2006-10-03 22:54:15 +0200213If it's really a bug, report it with the following information:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
215 - the name of the driver/card, show in /proc/asound/cards
Matt LaPlanted6bc8ac2006-10-03 22:54:15 +0200216 - the register dump, if available (e.g. card*/cmipci)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217
218when 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
223when it's a mixer problem,
224
225 - AC97 proc files, codec97#*/* files
226
227for USB audio/midi,
228
229 - output of lsusb -v
230 - stream* files in card directory
231
232
233The ALSA bug-tracking system is found at:
234
235 https://bugtrack.alsa-project.org/alsa-bug/