Re: snd-usb-audio in ALSA 0.9.0rc5

[Pedro Lopez-Cabanillas <plcl@telefonica.net>]

On Wednesday 13 November 2002 09:50, Clemens Ladisch wrote:
> Pedro Lopez-Cabanillas wrote:
> > IMHO, mapping the card MIDI ports to subdevices may be OK, but only for
> > ALSA native rawmidi. After all, you can access some MIDI port with
> > "hw:x,y,z" instead of "hw:x,y", but for OSS emulation a better approach
> > is needed. For major 14, why not to bind minors sequentially for each
> > MIDI port on the system? I mean: first port minor=2, second port
> > minor=18, ... thru -and up- minor=242 (/dev/midi15) if needed, regardless
> > of ALSA card numbers?
>
> This would break if cards are loaded dynamically, i.e. the port number
> would depend on the order the drivers are loaded.

Yes, but not only the driver's loading order matters. With USB devices, the 
hub's port number and the plug-in order may cause troubles, too. With my UM-2 
and Midisport2x2, both using snd-usb-audio driver, i was used to cat 
/proc/asound/seq/clients from time to time, to know which client number had 
each device, until i've found a solution that is the same as for driver 
loading order. This is a snippet from my modules.conf file:

alias char-major-14 soundcore
alias char-major-116 snd
alias snd-card-0 snd-ens1371
alias snd-card-1 snd-usb-audio
alias snd-card-2 snd-usb-audio
options snd cards_limit=3
options snd-ens1371 index=0
options snd-usb-audio index=1,2 vid=0x0763,0x0582 pid=0x1110,0x0005

Since i've found this trick, i don't need to wonder about client numbers as 
they always are the same. It doesn' matter which device i plug-in first, 
neither which USB hub port it uses. 72 is always Midisport and 80 is UM-2.

I don't know if there is a better way, and i'm not sure if it shall work  for 
OSS rawmidi also. 

> Well, for obvous reasons (i.e. laziness), the current answer for this is
> "don't use OSS".  ;-)

You're kidding :-) You made a great, tireless work with ALSA usb driver, and 
ALSA as a whole is going to be beautiful too... but there are a lot of worthy   
OSS legacy apps (i.e. PD), and many cheap and ubiquitous USB MIDI multiport 
devices now. IMHO, ALSA should be able to give support to both worlds.

Of course, this issue must be addressed very carefully, having some previous 
discussions with final consensus.

About device minor numbers, i've heard that Linux 2.6 shall break actual  
limitations, with a 32 bits kdev_t, divided up to 12 bits for major and 20 
bits for minor. Anybody can confirm this?

Regards,
Pedro

-- 
ALSA Library Bindings for Pascal
http://alsapas.alturl.com



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