[Intel-gfx] [PATCH 1/2] drm: Introduce per-device driver_features

[Michel Dänzer]

On 2018-09-13 4:29 p.m., Ville Syrjälä wrote:
> On Thu, Sep 13, 2018 at 03:50:01PM +0200, Daniel Vetter wrote:
>> On Thu, Sep 13, 2018 at 04:16:21PM +0300, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>>
>>> We wish to control certain driver_features flags on a per-device basis
>>> while still sharing a single drm_driver instance across all the
>>> devices. To that end introduce device.driver_features. By default
>>> it will be set to ~0 to not impose any limits beyond
>>> driver.driver_features. Drivers can then clear specific flags
>>> in the per-device bitmask to limit the capabilities of the device.
>>>
>>> An alternative approach would be to copy the driver_features from
>>> the driver into the device in drm_dev_init(), however that would
>>> require verifying that no driver is currently changing
>>> driver.driver_features after drm_dev_init(). Hence the ~0 apporach
>>> was easier.
>>>
>>> Ideally we'd also make drm_driver const but there is plenty of code
>>> left that wants to mutate it (eg. various vfunc assignments). We'll
>>> need to fix all that up before we can make it const.
>>>
>>> And while at it fix up the type of the feature flag passed to
>>> drm_core_check_feature().
>>>
>>> v2: Streamline the && vs. & (Chris)
>>>     s/int/u32/ in drm_core_check_feature() args
>>>
>>> Cc: Chris Wilson <chris at chris-wilson.co.uk>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>
>> git grep DRIVER_ATOMIC -- drivers/gpu/drm/nouveau has a 2nd supporting
>> case for this. Exactly same problem as we have here. Would be good to also
>> convert that one, for a bit of OCD.
> 
> Thanks for pointing it out. I'll cook it up and send separately after
> this lands.

I don't suppose you'd like to do amdgpu as well, while you're at it? :)

Either way, this is awesome stuff! This patch is

Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>


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