On Wed, 14 Jan 2009 10:44:38 -0600 (CST) Mike Isely <isely@xxxxxxxxx> wrote: > 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). While discussing the serial number patch, I've picked the other ones. > 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): > > Interesting... Yet, IMO, we should be more strict about bus_info. This can be used as a way to associate a /dev/<device> with their sysfs entry. > 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. Sorry, but I didn't understand the need. What do you want to map in userspace? Except for debugging purposes, or when the user has more than one device connected, I can't see any other usage for such identifier. For debug, you can just print the serial number. For device unique identification, there are the sysfs stuff, used by udev. Am I missing something? Cheers, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
