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Documentation / sound / alsa / Procfile.txt

Based on kernel version 2.6.26. Page generated on 2008-07-16 21:13 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.
92		This shows the status of xrun (= buffer overrun/xrun) debug of
93		ALSA PCM middle layer, as an integer from 0 to 2.  The value
94		can be changed by writing to this file, such as
95	
96			 # cat 2 > /proc/asound/card0/pcm0p/xrun_debug
97	
98		When this value is greater than 0, the driver will show the
99		messages to kernel log when an xrun is detected.  The debug
100		message is shown also when the invalid H/W pointer is detected
101		at the update of periods (usually called from the interrupt
102		handler).
103	
104		When this value is greater than 1, the driver will show the
105		stack trace additionally.  This may help the debugging.
106	
107	card*/pcm*/sub*/info
108		The general information of this PCM sub-stream.
109	
110	card*/pcm*/sub*/status
111		The current status of this PCM sub-stream, elapsed time,
112		H/W position, etc.
113	
114	card*/pcm*/sub*/hw_params
115		The hardware parameters set for this sub-stream.
116	
117	card*/pcm*/sub*/sw_params
118		The soft parameters set for this sub-stream.
119	
120	card*/pcm*/sub*/prealloc
121		The buffer pre-allocation information.
122	
123	
124	AC97 Codec Information
125	----------------------
126	
127	card*/codec97#*/ac97#?-?
128		Shows the general information of this AC97 codec chip, such as
129		name, capabilities, set up.
130	
131	card*/codec97#0/ac97#?-?+regs
132		Shows the AC97 register dump.  Useful for debugging.
133	
134		When CONFIG_SND_DEBUG is enabled, you can write to this file for
135		changing an AC97 register directly.  Pass two hex numbers.
136		For example,
137	
138		# echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs
139	
140	
141	USB Audio Streams
142	-----------------
143	
144	card*/stream*
145		Shows the assignment and the current status of each audio stream
146		of the given card.  This information is very useful for debugging.
147	
148	
149	HD-Audio Codecs
150	---------------
151	
152	card*/codec#*
153		Shows the general codec information and the attribute of each
154		widget node.
155	
156	
157	Sequencer Information
158	---------------------
159	
160	seq/drivers
161		Lists the currently available ALSA sequencer drivers.
162	
163	seq/clients
164		Shows the list of currently available sequencer clients and
165		ports.  The connection status and the running status are shown
166		in this file, too.
167	
168	seq/queues
169		Lists the currently allocated/running sequencer queues.
170	
171	seq/timer
172		Lists the currently allocated/running sequencer timers.
173	
174	seq/oss
175		Lists the OSS-compatible sequencer stuffs.
176	
177	
178	Help For Debugging?
179	-------------------
180	
181	When the problem is related with PCM, first try to turn on xrun_debug
182	mode.  This will give you the kernel messages when and where xrun
183	happened.
184	
185	If it's really a bug, report it with the following information:
186	
187	  - the name of the driver/card, show in /proc/asound/cards
188	  - the register dump, if available (e.g. card*/cmipci)
189	
190	when it's a PCM problem,
191	
192	  - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
193	    sub-stream directory
194	
195	when it's a mixer problem,
196	
197	  - AC97 proc files, codec97#*/* files
198	
199	for USB audio/midi,
200	
201	  - output of lsusb -v
202	  - stream* files in card directory
203	
204	
205	The ALSA bug-tracking system is found at:
206	
207	    https://bugtrack.alsa-project.org/alsa-bug/
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