Exposing GPU information for userspace processes

[Daniel Vetter]

On Wed, Jul 10, 2013 at 04:01:49PM +1000, Dave Airlie wrote:
> On Wed, Jul 10, 2013 at 7:45 AM, Rhyland Klein <rklein at nvidia.com> wrote:
> > We are currently looking into exporting some information from the linux
> > kernel to userspace about the GPU. This information is specific per
> > board as the data can vary depending on the fuses burnt on the board.
> >
> > Right now we are leaning towards adding sysfs properties to our existing
> > nodes to share this information.
> >
> > Before we write up the patches and update our userspace apps to check
> > the new locations, we wanted to make sure there wasn't a more
> > accepted/proper way to export information already.
> >
> > Right now for instance we want to export a property to say how many
> > pixel pipes there are. This could then be exported in something like:
> >
> > /sys/bus/platform/drivers/gr3d/54180000.gr3d/num_pixel_pipes
> >
> > Is this the best approach to take right now or is there another way we
> > should export this and similar HW specific information?
> 
> All the x86 GPU drivers use gpu specific get param ioctls for this so far.
> 
> e.g. drivers/gpu/drm/radeon/radeon_kms.c:radeon_info_ioctl

In drm/i915 we also expose a bunch of thing to sysfs, but everything that
the userspace drivers need for operation is exposed through the getparam
ioctl. We add sysfs interfaces on top if there's a legit reason for the
user to script changes (e.g. gpu error state collection or tuning the
frequency scaling and related read-only statistics).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch