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. Man
11 found in this tree. When you encounter a prob
12 check the files listed in the following sectio
13
14 Each card has its subtree cardX, where X is fr
15 card-specific files are stored in the ``card*`
16
17
18 Global Information
19 ==================
20
21 cards
22 Shows the list of currently configured
23 index, the id string, short and long d
24
25 version
26 Shows the version string and compile d
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 vi
36 Appears only when ``CONFIG_SND_DEBUG=y
37
38 hwdep
39 Lists the currently available hwdep de
40 ``<card>-<device>: <name>``
41
42 pcm
43 Lists the currently available PCM devi
44 ``<card>-<device>: <id>: <name> : <sub
45
46 timer
47 Lists the currently available timer de
48
49
50 oss/devices
51 Lists the OSS device mappings.
52
53 oss/sndstat
54 Provides the output compatible with /d
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/a
62 Some drivers (e.g. cmipci) have their own proc
63 register dump, etc (e.g. ``/proc/asound/card*/
64 dump). These files would be really helpful fo
65
66 When PCM devices are available on this card, y
67 like pcm0p or pcm1c. They hold the PCM inform
68 stream. The number after ``pcm`` is the PCM d
69 the last ``p`` or ``c`` means playback or capt
70 this subtree is described later.
71
72 The status of MIDI I/O is found in ``midi*`` f
73 name and the received/transmitted bytes throug
74
75 When the card is equipped with AC97 codecs, th
76 subdirectories (described later).
77
78 When the OSS mixer emulation is enabled (and t
79 oss_mixer file appears here, too. This shows
80 OSS mixer elements to the ALSA control element
81 mapping by writing to this device. Read OSS-E
82 details.
83
84
85 PCM Proc Files
86 ==============
87
88 ``card*/pcm*/info``
89 The general information of this PCM de
90 substreams, etc.
91
92 ``card*/pcm*/xrun_debug``
93 This file appears when ``CONFIG_SND_DE
94 ``CONFIG_SND_PCM_XRUN_DEBUG=y``.
95 This shows the status of xrun (= buffe
96 invalid PCM position debug/check of AL
97 It takes an integer value, can be chan
98 file, such as::
99
100 # echo 5 > /proc/asound/card0
101
102 The value consists of the following bi
103
104 * bit 0 = Enable XRUN/jiffies debug me
105 * bit 1 = Show stack trace at XRUN / j
106 * bit 2 = Enable additional jiffies ch
107
108 When the bit 0 is set, the driver will
109 kernel log when an xrun is detected.
110 shown also when the invalid H/W pointe
111 update of periods (usually called from
112 handler).
113
114 When the bit 1 is set, the driver will
115 additionally. This may help the debug
116
117 Since 2.6.30, this option can enable t
118 jiffies. This detects spontaneous inv
119 values, but can be lead to too much co
120 buggy) hardware that doesn't give smoo
121 This feature is enabled via the bit 2.
122
123 ``card*/pcm*/sub*/info``
124 The general information of this PCM su
125
126 ``card*/pcm*/sub*/status``
127 The current status of this PCM sub-str
128 H/W position, etc.
129
130 ``card*/pcm*/sub*/hw_params``
131 The hardware parameters set for this s
132
133 ``card*/pcm*/sub*/sw_params``
134 The soft parameters set for this sub-s
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
141 written to this proc file. Used for f
142 This entry is write-only.
143
144 AC97 Codec Information
145 ======================
146
147 ``card*/codec97#*/ac97#?-?``
148 Shows the general information of this
149 name, capabilities, set up.
150
151 ``card*/codec97#0/ac97#?-?+regs``
152 Shows the AC97 register dump. Useful
153
154 When CONFIG_SND_DEBUG is enabled, you
155 changing an AC97 register directly. P
156 For example,
157
158 ::
159
160 # echo 02 9f1f > /proc/asound/card0/co
161
162
163 USB Audio Streams
164 =================
165
166 ``card*/stream*``
167 Shows the assignment and the current s
168 of the given card. This information i
169
170
171 HD-Audio Codecs
172 ===============
173
174 ``card*/codec#*``
175 Shows the general codec information an
176 widget node.
177
178 ``card*/eld#*``
179 Available for HDMI or DisplayPort inte
180 Shows ELD(EDID Like Data) info retriev
181 and describes its audio capabilities a
182
183 Some ELD fields may be modified by doi
184 Only do this if you are sure the HDMI
185 And if that makes your HDMI audio work
186 can fix it in future kernel releases.
187
188
189 Sequencer Information
190 =====================
191
192 seq/drivers
193 Lists the currently available ALSA seq
194
195 seq/clients
196 Shows the list of currently available
197 ports. The connection status and the
198 in this file, too.
199
200 seq/queues
201 Lists the currently allocated/running
202
203 seq/timer
204 Lists the currently allocated/running
205
206 seq/oss
207 Lists the OSS-compatible sequencer stu
208
209
210 Help For Debugging?
211 ===================
212
213 When the problem is related with PCM, first tr
214 mode. This will give you the kernel messages
215 happened.
216
217 If it's really a bug, report it with the follo
218
219 - the name of the driver/card, show in ``/proc
220 - the register dump, if available (e.g. ``card
221
222 when it's a PCM problem,
223
224 - set-up of PCM, shown in hw_parms, sw_params,
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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