[Intel-gfx] [PATCH v2 1/3] drm: Add the optional .fb_modifier() hook

Michel Dänzer michel at daenzer.net
Tue Mar 13 15:35:02 UTC 2018

On 2018-03-13 04:20 PM, Daniel Vetter wrote:
> On Tue, Mar 13, 2018 at 03:38:38PM +0100, Michel Dänzer wrote:
>> On 2018-03-13 03:28 PM, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>> To make it possible for the core to check the fb pixel format and
>>> modifier, we need to first ask the driver to deduce the modifier
>>> when the request does not explicitly specify one.
>>> Add a new .fb_modifier() hook for that purpose and convert i915
>>> and vc4 to make use if it. All other drivers seem to currently
>>> assume linear when the request does not specify anything else,
>>> [...]
>> That's not true at least for the amdgpu and radeon drivers. The tiling
>> mode is communicated via BO metadata.
> But atm amdgpu and radeon also don't support explicit modifiers in the
> kernel driver, so it again all checks out. Or should at least.

Sounds like I misunderstood that this is trying to guess modifiers for
all drivers. So far, so good if so.

> Once you add modifier support, you need to wire up all the bits and the
> rigth default selection, and it should again pan out.

Well, this change allows a driver not to wire up the fb_modifier hook,
and just assumes linear in that case. Seems like an accident waiting to
happen, but I'll leave it to you guys.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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