Naming two identical USB devices (need help)

Naming two identical USB devices (need help)

[Jean-Michel Pouré]

Hello,

My need is very basic.

I am using two Terratec Aureon USB MK2 devices.
But this could be any case where two devices are the same.

My question is:

Is there a way to make sure that each physical device always has the
same name: plughw:0,0 (first identical card) and plughw:1,0 (second
identical card). This would allow me to plug the cards and forget the
plugs. 

Presently, numbers change on every reboot or if I hotplug devices.

I read on the wiki that it was possible to load modules in a precise
order. But it seems to be working in case of several ***different***
devices, not several identical devices:
http://alsa.opensrc.org/MultipleCards

Any idea? Is there a way to use Udev?

If it is not possible in the current state of Alsa, I will send back one
device to the retailer, in which case I need your kind advice quickly.

Kind regards,
Jean-Michel Pouré


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Re: Naming two identical USB devices (need help)

[Lee Revell]

On 2/9/07, Jean-Michel Pouré <jmpoure@free.fr> wrote:
> Hello,
>
> My need is very basic.
>
> I am using two Terratec Aureon USB MK2 devices.
> But this could be any case where two devices are the same.
>
> My question is:
>
> Is there a way to make sure that each physical device always has the
> same name: plughw:0,0 (first identical card) and plughw:1,0 (second
> identical card). This would allow me to plug the cards and forget the
> plugs.
>

I don't think there's an easy way with any current Linux distro.

Don't USB devices have some kind of hardware serial number or GUID
that udev could be taught about?

Lee

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Re: Naming two identical USB devices (need help)

[Jean-Michel Pouré]

Le vendredi 09 février 2007 à 21:25 -0500, Lee Revell a écrit :
> I don't think there's an easy way with any current Linux distro.
> 
> Don't USB devices have some kind of hardware serial number or GUID
> that udev could be taught about?
> 
> Lee 

Dear Alsa developpers,

udevinfo can handle serial ID.
It is very versatile.

But then the question is, how do I use Udev to teach Alsa how to set up
plughw:x,y numbers. It should be possible to rename PCMs using Udev. But
how do I rename plughw:x,y.

I searched on Google and the wiki without answers.

I can hardly imagine that professionnal hardware with several identical
cards cannot distinguish audio devices once for all.

I am very happy with Alsa, and I can wait a couple of months before Alsa
handles Udev better. But please inform me so that I can ship my second
card back.

Kind regards,
Jean-Michel


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Re: Naming two identical USB devices (need help)

[Ingo Müller]

Hi!

I thought about your problem again and I think I made a small progress!
I was able to set the cards number to any number I want using a udev
rule, so I could use that card with plughw:n,0 where n was the number of
my choise. I didn't use a udev rule that makes a lot of sense, but I'm
sure that there is a possibility to create a rule that depends on the
usb port your usb sound card is plugged in. Here is what I did:

I looked at the devices that where created before I did anything:

ingo@ingo-desktop:~$ls -l /dev/snd/
insgesamt 0
crw-rw---- 1 root audio 116, 11 2007-02-10 18:26 controlC0
crw-rw---- 1 root audio 116,  3 2007-02-10 18:26 hwC0D0
crw-rw---- 1 root audio 116, 13 2007-02-10 18:26 hwC0D2
crw-rw---- 1 root audio 116,  4 2007-02-10 18:26 midiC0D0
crw-rw---- 1 root audio 116, 14 2007-02-10 18:26 midiC0D1
crw-rw---- 1 root audio 116, 15 2007-02-10 18:26 midiC0D2
crw-rw---- 1 root audio 116, 10 2007-02-10 18:26 pcmC0D0c
crw-rw---- 1 root audio 116,  9 2007-02-10 18:26 pcmC0D0p
crw-rw---- 1 root audio 116,  8 2007-02-10 18:26 pcmC0D1c
crw-rw---- 1 root audio 116,  7 2007-02-10 18:26 pcmC0D2c
crw-rw---- 1 root audio 116,  6 2007-02-10 18:26 pcmC0D2p
crw-rw---- 1 root audio 116,  5 2007-02-10 18:26 pcmC0D3p
crw-rw---- 1 root audio 116, 12 2007-02-10 18:26 seq
crw-rw---- 1 root audio 116,  2 2007-02-10 18:26 timer

The I looked at the udev rules, that created these devices (in
/etc/udev/rules.d/20-names.rules):

# Sound devices, group under /dev/snd
KERNEL=="controlC[0-9]*",		NAME="snd/%k"
KERNEL=="hwC[D0-9]*",			NAME="snd/%k"
KERNEL=="midiC[D0-9]*",			NAME="snd/%k"
KERNEL=="pcmC[D0-9cp]*",		NAME="snd/%k"
KERNEL=="seq",				NAME="snd/%k"
KERNEL=="timer",			NAME="snd/%k"

These rules only "move" the sound devices to the snd/ directory. In
order to change the name of the created devices, I created a rule for
every device that has been created before, using its name from the first
ls command, and changed the card number (still moving it to snd/), here
it is number 3.

KERNEL=="controlC0",		NAME="snd/controlC3"
KERNEL=="hwC0D0",		NAME="snd/hwC3D0"
KERNEL=="hwC0D2",		NAME="snd/hwC3D2"
KERNEL=="midiC0D0",		NAME="snd/midiC3D0"
KERNEL=="midiC0D1",		NAME="snd/midiC3D1"
KERNEL=="midiC0D2",		NAME="snd/midiC3D2"
KERNEL=="pcmC0D0c",		NAME="snd/pcmC3D0c"
KERNEL=="pcmC0D0p",		NAME="snd/pcmC3D0p"
KERNEL=="pcmC0D1c",		NAME="snd/pcmC3D1c"
KERNEL=="pcmC0D2c",		NAME="snd/pcmC3D2c"
KERNEL=="pcmC0D2p",		NAME="snd/pcmC3D2p"
KERNEL=="pcmC0D3p",		NAME="snd/pcmC3D3p"

The result: My card was not card 0 anymore ("Karte 0"), but card 3
("Karte 3") and I was able to use it with plughw:3,0.

ingo@ingo-desktop:~$aplay -l
**** Liste von PLAYBACK Geräten ****
Karte 3: Live [SBLive! Platinum [CT4760P]], Gerät 0: emu10k1 [ADC
Capture/Standard PCM Playback]
  Untergeordnete Geräte: 32/32
  Untergeordnetes Gerät '0: subdevice #0
  Untergeordnetes Gerät '1: subdevice #1
  Untergeordnetes Gerät '2: subdevice #2
  Untergeordnetes Gerät '3: subdevice #3
...

That means that there is a way to influence the number of the card with
udev! Now, everything you have to do is find a udev rule that matches a
certain usb port. As you can run external programs with udev, there must
be a way to do that.

I'm going to play with udev now, too, so if I find something, I'll tell
you. In return, it would be awesome if you could write down - even it is
only short - a howto about how to manage two identical devices, once we
got it working.

Regards, Ingo



Jean-Michel Pouré schrieb:
> Hello,
> 
> My need is very basic.
> 
> I am using two Terratec Aureon USB MK2 devices.
> But this could be any case where two devices are the same.
> 
> My question is:
> 
> Is there a way to make sure that each physical device always has the
> same name: plughw:0,0 (first identical card) and plughw:1,0 (second
> identical card). This would allow me to plug the cards and forget the
> plugs. 
> 
> Presently, numbers change on every reboot or if I hotplug devices.
> 
> I read on the wiki that it was possible to load modules in a precise
> order. But it seems to be working in case of several ***different***
> devices, not several identical devices:
> http://alsa.opensrc.org/MultipleCards
> 
> Any idea? Is there a way to use Udev?
> 
> If it is not possible in the current state of Alsa, I will send back one
> device to the retailer, in which case I need your kind advice quickly.
> 
> Kind regards,
> Jean-Michel Pouré


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Re: Naming two identical USB devices (need help)

[Ingo Müller]

Hi!

I found a command that may be very usefull to create a udev rule:

udevinfo -a -p $(udevinfo -q path -n <path-to-current-device-node>)

If I get it right, it displays everything you can use to create udev
rules (except external programs). I've run it for a non sound card usb
device and it lists the usb port! If youre lucky, there is even an
unique identifier - just compare the output of the two devices.

Regards, Ingo



Ingo Müller schrieb:
> I'm going to play with udev now, too, so if I find something, I'll tell
> you.

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Re: Naming two identical USB devices (need help)

[Jean-Michel Pouré]

Le samedi 10 février 2007 à 18:53 +0100, Ingo Müller a écrit :
> I'm going to play with udev now, too, so if I find something, I'll
> tell
> you. In return, it would be awesome if you could write down - even it
> is
> only short - a howto about how to manage two identical devices, once
> we
> got it working.
> 

Fantastic.

Thank you very much for your help.
I will add a page on the wiki about udev rules.

Kind regards,
Jean-Michel


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