sound/designs/oss-emulation.rst

2 Notes on Kernel OSS-Emulation
11 ALSA provides a powerful OSS emulation on the kernel.
12 The OSS emulation for PCM, mixer and sequencer devices is implemented
13 as add-on kernel modules, snd-pcm-oss, snd-mixer-oss and snd-seq-oss.
14 When you need to access the OSS PCM, mixer or sequencer devices, the
22 Only necessary step for auto-loading of OSS modules is to define the
32 The currently available OSS configuration is shown in
33 /proc/asound/oss/sndstat.  This shows in the same syntax of
34 /dev/sndstat, which is available on the commercial OSS driver.
38 after the corresponding OSS-emulation module is loaded.  Don't worry
45 ALSA supports the following OSS device files:
66 /dev/midi1.  They are NOT for OSS but for tclmidi, which is
69 Unlike the real OSS, ALSA cannot use the device files more than the
79 snd-pcm-oss and snd-rawmidi.  In the case of PCM, the following
80 options are available for snd-pcm-oss:
93 	options snd-pcm-oss adsp_map=2
100 	options snd-pcm-oss adsp_map=0,2
122 As default, ALSA emulates the OSS PCM with so-called plugin layer,
130 stream, ``/proc/asound/cardX/pcmY[cp]/oss``, where X is the card number
133 exists only after snd-pcm-oss module is loaded.
171 	% echo "quake 0 0 direct" > /proc/asound/card0/pcm0p/oss
177 	% echo "quake 0 0 disable" > /proc/asound/card0/pcm0c/oss
186 As default, ALSA behaves as original OSS drivers, i.e. does not block
190 module option of snd-pcm-oss.  For using the blocking mode as default
191 for OSS devices, define like the following:
194 	options snd-pcm-oss nonblock_open=0
207 	% cat /proc/asound/card0/pcm0p/oss > /somewhere/oss-cfg
212 	% cat /somewhere/oss-cfg > /proc/asound/card0/pcm0p/oss
218 	% echo "erase" > /proc/asound/card0/pcm0p/oss
225 OSS mixer is relatively complicated.  ALSA builds up a mixer element
231 OSS is changed, all the volume and switch controls above are adjusted
234 As default, ALSA uses the following control for OSS volumes:
237 OSS volume		ALSA control		Index
281 where the first column is the OSS volume element, the second column
284 corresponding OSS control is not available.
311 capture, the OSS API provides no way to set the format, sample rate or
336 on OSS.