[linux-dvb] Re: DVB-USB-T and 2.6

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Thursday 11 March 2004 00:19, John Dalgliesh wrote:
> On Wed, 10 Mar 2004, Andrew de Quincey wrote:
> > On Wednesday 10 March 2004 12:07, Andrew de Quincey wrote:
> > > Hi, I've just tried my USB DVB-T device under kernel 2.6.. no go; it
> > > just seems to hang when I insert the dvb-ttusb-budget module.
> > >
> > > I've tried 2.6.0 -> 2.6.3. Oh, and this is with the latest dvb-kernel
> > > from CVS (making sure DVB is NOT enabled in the kernel itself).
> > >
> > > I see there are some 2.6 fixes in there, so I assume those were for a
> > > -pre version of 2.6... does anyone know which?
> >
> > Ah, I think I've found it.... ttusb_probe() calls
> > usb_set_configuration().
> >
> > In the source for usb_set_configuration(), it says specifically:
> > " * This call is synchronous. The calling context must be able to sleep,
> >  * and must not hold the driver model lock for USB; usb device driver
> >  * probe() methods may not use this routine."
> >
> > Sounds like the device init needs rearranged... maybe move the actual
> > device initialisation to the first stc_open() call. Can anyone with more
> > USB experience confirm this?
>
> OK I don't have much USB experience, but I know that on Darwin at least,
> setting the configuration demolishes all the existing USBInterfaces (on
> the USBDevice), and then creates new ones corresponding to the new
> configuration.
>
> So setting a configuration like that probably isn't what you want to do
> once you've matched to an interface - which the kernel 2.6 code looks like
> it does - although I guess it doesn't hurt if you only have one
> configuration anyway.
>
> As far as I can tell, the (conceptual) hierarchy of things USB goes:
> [USBDevice] x [configuration value] x [USBInterface] x [alternate setting]
> x [USBPipe]
>
> where the choice on a previous stage affects the options on the next ...
> but I'm a little hazy on the last couple of stages :)

Actually, that would explain another weird phenomenon I was seeing; two USB-Ts 
are showing up under 2.6, when I've only plugged one in. The first works, the 
second doesn't. Maybe I should remove the set/reset_configuration() call 
entirely?

> btw the TT USB devices do seem to have two USBInterfaces however...

Yep.. I assume one default interface, and one for when its up and running.


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