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Based on kernel version 4.0. Page generated on 2015-04-14 21:26 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/
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