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Based on kernel version 3.16. Page generated on 2014-08-06 21:41 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		  bit 3 = Log hwptr update at each period interrupt
105		  bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr()
106		  bit 5 = Show last 10 positions on error
107		  bit 6 = Do above only once
108	
109		When the bit 0 is set, the driver will show the messages to
110		kernel log when an xrun is detected.  The debug message is
111		shown also when the invalid H/W pointer is detected at the
112		update of periods (usually called from the interrupt
113		handler).
114	
115		When the bit 1 is set, the driver will show the stack trace
116		additionally.  This may help the debugging.
117	
118		Since 2.6.30, this option can enable the hwptr check using
119		jiffies.  This detects spontaneous invalid pointer callback
120		values, but can be lead to too much corrections for a (mostly
121		buggy) hardware that doesn't give smooth pointer updates.
122		This feature is enabled via the bit 2.
123	
124		Bits 3 and 4 are for logging the hwptr records.  Note that
125		these will give flood of kernel messages.
126	
127		When bit 5 is set, the driver logs the last 10 xrun errors and
128		the proc file shows each jiffies, position, period_size,
129		buffer_size, old_hw_ptr, and hw_ptr_base values.
130	
131		When bit 6 is set, the full xrun log is shown only once.
132	
133	card*/pcm*/sub*/info
134		The general information of this PCM sub-stream.
135	
136	card*/pcm*/sub*/status
137		The current status of this PCM sub-stream, elapsed time,
138		H/W position, etc.
139	
140	card*/pcm*/sub*/hw_params
141		The hardware parameters set for this sub-stream.
142	
143	card*/pcm*/sub*/sw_params
144		The soft parameters set for this sub-stream.
145	
146	card*/pcm*/sub*/prealloc
147		The buffer pre-allocation information.
148	
149	
150	AC97 Codec Information
151	----------------------
152	
153	card*/codec97#*/ac97#?-?
154		Shows the general information of this AC97 codec chip, such as
155		name, capabilities, set up.
156	
157	card*/codec97#0/ac97#?-?+regs
158		Shows the AC97 register dump.  Useful for debugging.
159	
160		When CONFIG_SND_DEBUG is enabled, you can write to this file for
161		changing an AC97 register directly.  Pass two hex numbers.
162		For example,
163	
164		# echo 02 9f1f > /proc/asound/card0/codec97#0/ac97#0-0+regs
165	
166	
167	USB Audio Streams
168	-----------------
169	
170	card*/stream*
171		Shows the assignment and the current status of each audio stream
172		of the given card.  This information is very useful for debugging.
173	
174	
175	HD-Audio Codecs
176	---------------
177	
178	card*/codec#*
179		Shows the general codec information and the attribute of each
180		widget node.
181	
182	card*/eld#*
183		Available for HDMI or DisplayPort interfaces.
184		Shows ELD(EDID Like Data) info retrieved from the attached HDMI sink,
185		and describes its audio capabilities and configurations.
186	
187		Some ELD fields may be modified by doing `echo name hex_value > eld#*`.
188		Only do this if you are sure the HDMI sink provided value is wrong.
189		And if that makes your HDMI audio work, please report to us so that we
190		can fix it in future kernel releases.
191	
192	
193	Sequencer Information
194	---------------------
195	
196	seq/drivers
197		Lists the currently available ALSA sequencer drivers.
198	
199	seq/clients
200		Shows the list of currently available sequencer clients and
201		ports.  The connection status and the running status are shown
202		in this file, too.
203	
204	seq/queues
205		Lists the currently allocated/running sequencer queues.
206	
207	seq/timer
208		Lists the currently allocated/running sequencer timers.
209	
210	seq/oss
211		Lists the OSS-compatible sequencer stuffs.
212	
213	
214	Help For Debugging?
215	-------------------
216	
217	When the problem is related with PCM, first try to turn on xrun_debug
218	mode.  This will give you the kernel messages when and where xrun
219	happened.
220	
221	If it's really a bug, report it with the following information:
222	
223	  - the name of the driver/card, show in /proc/asound/cards
224	  - the register dump, if available (e.g. card*/cmipci)
225	
226	when it's a PCM problem,
227	
228	  - set-up of PCM, shown in hw_parms, sw_params, and status in the PCM
229	    sub-stream directory
230	
231	when it's a mixer problem,
232	
233	  - AC97 proc files, codec97#*/* files
234	
235	for USB audio/midi,
236	
237	  - output of lsusb -v
238	  - stream* files in card directory
239	
240	
241	The ALSA bug-tracking system is found at:
242	
243	    https://bugtrack.alsa-project.org/alsa-bug/
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