Re: oss raw midi emulation

[Takashi Iwai <tiwai@suse.de>]

At Sun, 28 Nov 2004 12:14:24 -0300,
Carlos Pita wrote:
> 
> Hi!
> 
> What should be /dev/midi??   ?
> Symlimks to /dev/snd/midiC?D?  ?

No, it's an ALSA rawmidi device.  It accepts totally different ioctls,
etc although read/write controls are almost identical.

> Or devices with the correct major/minor numbers specified by the oss manual ?

Yes.  It should be cdev with major 14 & minor (2 + n * 16) 

> I'm asking because I need to use snd-virmidi in order to connect pd (which has no support
> for alsa midi yet) with muse or vkeybd. So I'm doing:
> 
> > modprobe snd-virmidi
> > cat /proc/asound/devices
>   [...]
>   43: [1- 3]: raw midi
>   42: [1- 2]: raw midi
>   41: [1- 1]: raw midi
>   40: [1- 0]: raw midi
> > ln -s /dev/snd/midiC1D0 /dev/midi10
> > pd -midiindev 11
> (with -midiindev N,  pd will open /dev/midiM with M=N-1, just a quirk)
> Then I aconnect muse or vkeybd to alsa client VirMIDI 1-0.
> 
> It works fine, but is this the right way to do it? For me it was
> a matter of trial and error.
> 
> Also, debian sarge predefines the following four devices:
> 
> crw-rw----  1 root audio 14,  2 2004-10-26 21:40 /dev/midi00
> crw-rw----  1 root audio 14, 18 2004-10-26 21:40 /dev/midi01
> crw-rw----  1 root audio 14, 34 2004-10-26 21:40 /dev/midi02
> crw-rw----  1 root audio 14, 50 2004-10-26 21:40 /dev/midi03
> 
> which suggests that /dev/midi?? shouldn't be symlinked as I'm
> doing with /dev/midi10.

No, definitely not.

The device assignment is different between ALSA and OSS.
ALSA assigns multiple devices per card, but OSS has basically no
concept of cards, so the currently OSS emulation assigns up to two
device per card for /dev/midi0? and /dev/amidi0?.

Instead of symlinks, the applications should be able to point
different paths for devices...


Takashi


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