On Wednesday 14 January 2009 17:44:38 Mike Isely wrote:
> On Wed, 14 Jan 2009, Mike Isely wrote:
> > On Wed, 14 Jan 2009, Mauro Carvalho Chehab wrote:
> >
> > [...]
> >
> > > I can see some troubles here:
> > >
> > > 1) The bus info helps to identify the place where you'll find the
> > > device info at sysfs;
> > >
> > > 2) This is a V4L2 API non-compliance. All drivers should be
> > > compliant with the API;
> > >
> > > 3) If we all agree that bus_info doesn't matter at all and decide
> > > to change V4L2 API, we'll still have a big trouble: most devices
> > > don't have a serial number.
> > >
> > > The other patches are ok.
> >
> > I was asked to make this change, because otherwise there's no means
> > via the V4L interface to uniquely REPEATABLY be able to identify
> > the same device each time it is plugged in. I have gotten
> > complaints about this. I actually pointed out that bus_info was
> > about the "where" not the "what" of the device, but I was convinced
> > to change this - after being surprised that the V4L spec allowed
> > for this. Look at the online v4l spec; the following description
> > exists about bus_info (as part of the VIDIOC_QUERYCAP description):
>
> [...]
>
> Mauro:
>
> If you still don't like this specific changeset, then OK, but I'd
> still appreciate it if you could pull the other changes (especially
> the v4l2_subdev fix).
Mauro,
I agree with Mike on this: please pull at least the v4l2_subdev fix
which must go asap to 2.6.29 as well. It's a very embarrassing bug that
I introduced and that Mike found (thanks Mike!).
Regards,
Hans
> And I'd appreciate some suggestions from anyone about a means via the
> V4L interface to make available a device-specific identifier, like a
> serial number. Yes I know such a thing is not always available with
> all devices, but it is available for Hauppauge devices in general and
> users want to have access to that information for purposes of mapping
> behavior in userspace.
>
> -Mike
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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