On Wed, Nov 23, 2016 at 03:17:53PM +0100, Daniel Vetter wrote: > On Wed, Nov 23, 2016 at 03:58:34PM +0200, Jani Nikula wrote: > > On Wed, 23 Nov 2016, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > > On Wed, Nov 23, 2016 at 03:37:24PM +0200, Jani Nikula wrote: > > >> On Tue, 22 Nov 2016, Manasi Navare <manasi.d.navare@xxxxxxxxx> 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... > > > > I know, I know, I had that written in my mail already, but swallowed it > > not to add another dependency on another new UABI... we can do that > > later. > > In principle I'd agree, but the trouble with dp compliance is that the CTS > expects us to do stupid shit sometimes, like that test pattern forced as > 6bpc. So if we decode&handle everything in userspace then the question is > how to feed all those special cases back into the kernel, which means more > debugfs interfaces. Just going in the other direction. > > Given that it's a bit a toss-up unfortunately, and the current approach > seems reasonable. The kernel could of course parse whatever is needed from the test request as well, but leave it up to userspace to initiate the actual test and ack/nack the test request. So I don't see a real need for a debugfs interface in either direction. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
