Re: [PATCH 5/5] drm/i915: Add support for DP Video pattern compliance tests

Ville Syrjälä
2016-11-23T13:42:55Z

On Wed, Nov 23, 2016 at 03:37:24PM +0200, Jani Nikula wrote:
> On Tue, 22 Nov 2016, Manasi Navare <manasi.d.navare@intel.com> wrote:
> > The intel_dp_autotest_video_pattern() function gets invoked through the
> > compliance test handler on a HPD short pulse if the test type is
> > set to DP_TEST_VIDEO_PATTERN. This performs the DPCD registers
> > reads to read the requested test pattern, video pattern resolution,
> > frame rate and bits per color value. The results of this analysis
> > are handed off to userspace so that the userspace app can set the
> > video pattern mode appropriately for the test result/response.
> >
> > The compliance_test_active flag is set at the end of the individual
> > test handling functions. This is so that the kernel-side operations
> > can be completed without the risk of interruption from the userspace
> > app that is polling on that flag.
>
> I've brought this up before, but I think for this stuff the way to go is
> to have the userspace read the DPCD directly. We have the dev node for
> it.
>
> With the approach in this patch, we'll just end up reading a bunch of
> stuff from DPCD in kernel, doing error handling for that, decoding and
> sanity checking the values, putting them in debugfs for the userspace to
> read, having userspace code read debugfs, doing error handling for that,
> decoding and sanity checking the data, finally doing something based on
> the data.
>
> You'll also get a *much* faster turnaround for getting your userspace
> code done than getting all of this in kernel first, then tweaking your
> userspace, having to update both of those in lockstep, etc. When this is
> based on reading DPCD directly, you can just add new stuff quickly in
> userspace, with no kernel dependency.
>
> The easiest way would be to have an indication in debugfs for userspace
> that there's something interesting in DPCD. Just a simple thing.

Or just have the kernel fire off an uevent...

--
Ville Syrjälä
Intel OTC