Specifying the order of sound devices

[Scott James Remnant]

On Mon, 2006-04-10 at 07:53 +0200, Martin Pitt wrote:

> Lee Revell [2006-04-07 14:58 -0400]:
> > It seems that udev should be able to handle this but I don't see any way
> > for humans to configure it ;-)  It's a real pain because every distro
> > does it differently and none of them seem to have an easy way.
> 
> There is no particular 'Ubuntu way' of forcing a sound card ordering,
> and udev currently does not support that, so you have to do manual
> modprobe hacking to achieve that effect. However, the real bug is apps
> relying on a particular sound card order in the first place.
> 
Just to clarify on this; udev will *never* support forcing ordering of
module loading.  It's usually requested for one of two reasons, here's
why they are both invalid:

 1) two drivers are loaded for one card, and the order matters (e.g.
    bttv, orinoco, etc.)  The order shouldn't matter, this is clearly a
    bug in the driver and we'd much rather just have that fixed.  This
    isn't a solution because you may have two pieces of hardware, one
    supported by each driver.  One of those pieces of hardware might be
    removable, how do you force the module loading order when the user
    doesn't plug in the second device until an hour after they booted
    (and the driver for the first device was loaded).

 2) forcing the order in which two different devices of the same class
    are enumerated (e.g. network cards, sound cards, etc.)  Software
    should instead be modified to address devices by something other
    than their kernel enumeration (e.g. MAC address, etc.) and present
    the user with a list of potential devices.

    The GNOME CD writing apps are "gold star" pupils in this regard;
    they don't bore you with /dev/sda1 type messages -- they just give
    you a list of your recorders product names, and you pick the right
    one.

    Again, the fundamental reason this cannot be fixed is removable
    devices.  How do you cope with the removable device being "zero" and
    the built-in device being "one"?  Would you prevent the internal
    sound card from working unless the removable USB device was present?

    It's better to not have any concept of a "primary" or "default"
    device and just let applications select their target audio device.

    I heard some whisperings that GNOME was considering per-app volume
    settings; wouldn't it be great it you could adjust the volume in
    Rhythmbox to be quieter than the system beeps.

    I think it'd also be great it you could select per-add audio
    devices, so you could tell Rhythmbox to send the audio to your USB
    headset for a while, etc.

Scott
-- 
Scott James Remnant
scott at ubuntu.com

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