On Fri, Jan 20, 2017 at 06:28:39PM +0000, Emil Velikov wrote: > On 20 January 2017 at 16:17, Thierry Reding <treding@xxxxxxxxxx> wrote: > > On Fri, Jan 20, 2017 at 02:13:00PM +0000, Emil Velikov wrote: > >> On 19 January 2017 at 09:19, Thierry Reding <treding@xxxxxxxxxx> wrote: > >> > On Wed, Jan 18, 2017 at 02:59:21PM +0100, Neil Armstrong wrote: > >> >> Add support for Amlogic Meson DRM driver merged for Linux 4.10. > >> >> > >> >> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx> > >> >> --- > >> >> tests/util/kms.c | 1 + > >> >> 1 file changed, 1 insertion(+) > >> > > >> > Applied, thanks. > >> > > >> Was going to say "NACK use Thierry's helpers" but you've beat me to it. > >> As a Tl;DR: we _really_ want to stop using drmOpen* for anything that's KMS. > > > > I think it's still useful to have this helper to iterate over all > > supported driver because it enables easy testing with just a simple > > modetest. > > > > That said, for (almost) as long as I remember I've been using the -M > > option to prevent modetest from iterating over the list, which can take > > fairly long if you've got DRM_DEBUG messages enabled. > > > > I'm not sure I understand exactly what you're suggesting by "use > > Thierry's helpers". modetest and other tests use util_open() internally > > now. That in turn uses drmOpen(), though we're of course open to change > > that. Are you suggesting we somehow use drmDevice to locate existing > > devices? > > > Yes using drmDevice is what I had in mind. The only thing that was > stopping me from doing that is the lack of platform devices support. > With that in we can start purging _everything_ that uses drmOpen*. > > > We could implement some heuristic that finds the first device with a > > primary node, but what if we want to support the -M option? There is > > currently no way of getting the driver from drmDevice. Maybe that's > > something we should add anyway. > > > The -M (kernel module name as given by drmGetVersion) is another > interesting topic. Feel free to skip to the Tl;Dr below. > > If doing the ioctl implicitly via drmOpen or drmDevice wakes up the > device, keeping in mind that: > - it can take some time, and > - you don't always need the info > > A couple of elaborate workarounds include: > - use only on demand - add DRM_DEVICE_GET_MODULE_NAME or alike to the > drmDevice2 API > Needs a big "this can be VERY slow" warning in the documentation/man > pages... first we need actual man pages for libdrm ;-) > - deprecate the whole thing and use the compat strings - how do we > handle the PCI devices ? > - use the kernel module name (foo.ko) - kind of making it an ABI, but > iirc we've already have users which depend on it > Neither PCI devices nor platform ones are consistent in their naming - > foo.ko vs the value returned by the IOCTL. > > We might be able to combine the latter two ... need to double-check. > > Tl;Dr: For the moment I'd leave it to the user to call drmGetVersion. Okay, sounds like a plan. The good thing is we can keep adding new module names to the util_open() helper irrespective of when we change the implementation to use drmDevice instead of drmOpen() since it is conveniently encapsulated in a single function across libdrm. Thierry
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