[PATCH 2/6] drm: Refactor setplane to allow internal use (v3)

Daniel Vetter daniel at ffwll.ch
Thu May 22 15:37:52 PDT 2014

On Thu, May 22, 2014 at 6:33 PM, Matt Roper <matthew.d.roper at intel.com> wrote:
> v3:
>  - Move integer overflow checking from setplane_internal to setplane
>    ioctl.  The upcoming legacy cursor support via universal planes needs
>    to maintain current cursor ioctl semantics and not return error for
>    these extreme values (found via intel-gpu-tools kms_cursor_crc test).

Imo that's just the test being silly. I think it's valid to reject
such nonsense with -EINVAL and limit the random-walk range of our
testcase a bit. The igt testcases are just guidelines for what our ABI
is, but not the hard rules. And clarifying the ABI in such cases is
imo the right approach.

That random-walk testcase just was meant to test correctly clamping.
E.g. on hardware with just 12bit for the cursor placement we'd wrap
around and show a cursor again that should be off. So as long as you
still test that you can restrict the range of the test a bit.
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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