Re: /sbin/hotplug invocation for USB devices in 2.5.40

[David Brownell <david-b@pacbell.net>]

>>  - Don't make hotplug calls for USB devices until we have something
>>    for them to do.  (Essentially these are a new class of event.)
> 
> 
> Why not?  That lets us load drivers based on vendor and product id.  The
> interface specific calls let us load protocol specific drivers, giving
> us a semblance of heirachy that a lot of people used to want a few years
> ago (and Johannes provided a patch for a long time ago.)

I didn't know we had any problems loading drivers based on vendor+product ...
sure seems like I've been doing it for a few years now!

Today's MODULE_DEVICE_TABLE, with flags, should be isomorphic to as much
of a hierachy as is really needed.  I seem to recall Johannes saying his
patch didn't do everything MSFT seemed to say needed doing, either.



>>    The example that comes to mind is policy agents using those
>>    events to choose a non-default device configuration.  But USB
>>    needs a bunch of work before such things become practical.
> 
> 
> The USB core needs it?  Or the hotplug scripts?
> 
> I'm curious about this, as I'm looking at a device that might need to
> have it's second configuration enabled if it's running on Linux, yet the
> default config is for when running on Windows.

The usbcore code is pretty confused about changing configurations.
As I recall, it doesn't even bother unbinding drivers from the
first configuration's interfaces when it sets a new config, so
it's just accidental if it works safely (no drivers bound yet,
no urbs in progresss, and so on).

- Dave




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