[PATCH libdrm] tests: fix MAKE_RGBA macro for 10bpp modes

[Ilia Mirkin]

On Thu, Nov 23, 2017 at 2:09 PM, Ville Syrjälä
<ville.syrjala at linux.intel.com> wrote:
> On Thu, Nov 23, 2017 at 01:59:28PM -0500, Ilia Mirkin wrote:
>> We need to shift the values up, otherwise we'd end up with a negative
>> shift. This works for up-to 16-bit components, which is fine for now.
>
> Shouldn't we actually replicate the high bits in the low bits?

Not entirely sure what you're proposing...

Ideally we wouldn't be lazy and pass e.g. 16-bit values to MAKE_RGBA
which would then shift down as necessary (and even there, you could
end up with off-by-1's maybe?). For e.g. 0xff, that should become
0x3ff but with my code will become 0x3fc. But for other values, it's
less clear what to do with the low bits. I figured it didn't really
matter.

Do you have a concrete proposal?

  -ilia