[PATCH libdrm] xf86drm: Make drmNodeIsDRM() public.

[Christopher James Halse Rogers]

On 18 December 2018 5:03:22 am AEDT, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>Hi Christopher,
>
>On Tue, 20 Nov 2018 at 04:30, Christopher James Halse Rogers
><christopher.halse.rogers at canonical.com> wrote:
>>
>> I have wanted this code in Mir, so it's plausibly useful elsewhere,
>> particularly if the DRM device major number is going to become
>> dynamic.
>>
>Can you elaborate/link to the code that uses the major/minor?
>Fiddling with those manually is rather error prone most often than not.

We have an internal API that mirrors that of logind - taking a (major,minor) pair and returning a usable fd. For input devices, that just means opened O_NONBLOCK; for DRM devices it means calling SetMaster.

Here's the relevant (non-logind) implementation: https://github.com/MirServer/mir/blob/master/src/server/console/linux_virtual_terminal.cpp#L634

Since we by necessity end up pulling out the devnode I guess we could match on a /dev/dri prefix instead. I just noticed this function while doing the drmIsMaster patch and thought it would be convenient for us!