On 9/12/19 4:57 PM, Philipp Zabel wrote: > On Thu, 2019-09-12 at 16:49 +0200, Hans Verkuil wrote: >> On 9/12/19 4:21 PM, Mauro Carvalho Chehab wrote: >>> Em Thu, 12 Sep 2019 14:16:11 +0100 >>> Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx> escreveu: >>> >>>> Hi Hans, >>>> >>>> On 12/09/2019 08:48, Hans Verkuil wrote: >>>>> Hi all, >>>>> >>>>> I am increasingly unhappy about the choice of /dev/videoX for metadata devices. >>>>> >>>>> It is confusing for end-users (especially w.r.t. the common uvc driver) and >>>>> if we want to change this, then we need to do it soon. >>> >>> Kernel has (about) nothing to do with how the userspace devnodes are >>> named, as the actual name is given by udev. >> >> To my knowledge the standard udev rules do not rename anything for media >> devices, so in reality it IS the kernel that decides this. >> >> But this is why I suggested to put it under a kernel config option. >> >>> >>> Anyway, from Kernel standpoint, it sounds too late to change the name >>> of the devices from "videoX" to something else, as a change like that >>> may break existing apps. >>> >>> It could make sense to have something like that at udev rules. >> >> But wouldn't that break existing apps as well? >> >> A bigger problem is that it isn't easy to detect the difference between >> a regular video device and a metadata device: you'd have to call QUERYCAP >> to determine that. > > v4l_id does call VIDIOC_QUERYCAP [1] to fill the ID_V4L_CAPABILITIES > colon separated list. > > [1] https://github.com/systemd/systemd/blob/master/src/udev/v4l_id/v4l_id.c#L66 Interesting. It's very outdated, though. Regards, Hans > > regards > Philipp >
