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 regards Philipp
