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

[John Dalgliesh <johnd@syd.microforte.com.au>]

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 :)

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{P^/

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


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