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

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

On Thu, 11 Mar 2004, Andrew de Quincey wrote:
> On Thursday 11 March 2004 01:44, John Dalgliesh wrote:
> > On Thu, 11 Mar 2004, Andrew de Quincey wrote:
> > > On Thursday 11 March 2004 00:19, John Dalgliesh wrote:
> > > > 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?
> >
> > Yep, I reckon you should just remove that line (under 2.6) and see if it
> > works :)
>
> Yep, sounds good to me. And it did. I now have only one adapter :)

Cool.

> > Also I think you should use the 'probe' method to discard the interface
> > that you don't want. According to the ttusb_setup_interfaces method it
> > looks like it really wants to run as interface index #1. So if the
> > usb_interface passed into probe isn't this index then it's not the one you
> > want (and you don't need to call usb_set_interface either).
>
> You're right about checking the interface number (I think).. just in case I
> get passed interface #0 (but I doubt I will; I guess the kernel claims that
> one for device configuration). The speedtch USB ADSL modem driver does this
> check in 2.6.
>
> However, I think I do have to call usb_set_interface to choose the correct
> altsetting for interface 1. There seem to be loads of different possible
> altsettings for interface 1, so I'd better ensure the correct one is chosen.

Oh right, so that sets the 'alternate setting' thingy... ok yeah you need
that then :)

I thought it was some backwards-compatibility trick so you could address
a device as if it were an interface. But it has two '1' arguments there.
My mistake.


{P^/

btw It's incredibly timely (again!) that you went and fixed up this driver
right now... I started on the Mac driver for budget TT USB devices on the
weekend, but when I had a look to see what the linux driver was doing I
got really confused - I couldn't understand how changing the configuration
value like that was supposed to work. And that's because it didn't :)


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