[PATCH] drm/amdgpu/dc: Pixel encoding DRM property and module parameter

[Harry Wentland]

On 2020-09-25 5:18 p.m., Alex Deucher wrote:
> On Tue, Sep 22, 2020 at 4:51 PM James Ettle <james at ettle.org.uk> wrote:
>>
>> On 22/09/2020 21:33, Alex Deucher wrote:
>>>> +/**
>>>> + * DOC: pixel_encoding (string)
>>>> + * Specify the initial pixel encoding used by a connector.
>>>> + */
>>>> +static char amdgpu_pixel_encoding[MAX_INPUT];
>>>> +MODULE_PARM_DESC(pixel_encoding, "Override pixel encoding");
>>>> +module_param_string(pixel_encoding, amdgpu_pixel_encoding, sizeof(amdgpu_pixel_encoding), 0444);
>>>
>>> You can drop this part.  We don't need a module parameter if we have a
>>> kms property.
>>>
>>> Alex
>>
>> OK, but is there then an alternative means of setting the pixel encoding to be used immediately on boot or when amdgpu loads? Also are there user tools other than xrandr to change a KMS property, for Wayland and console users?
> 
> You can force some things on the kernel command line, but I don't
> recall whether that includes kms properties or not.  As for ways to
> change properties, the KMS API provides a way.  those are exposed via
> randr when using X.  When using wayland compositors, it depends on the
> compositor.
> 

I'm not aware of a way to specify KMS properties through the kernel
command line. I don't think it's possible.

For atomic userspace the userspace wants to be the authority on the KMS
config. I'm not sure there's a way to set these properties with Wayland
unless a Wayland compositor plumbs them through.

Can you summarize on a higher level what problem you're trying to solve?
I wonder if it'd be better solved with properties on a DRM level that
all drivers can follow if desired.

Harry

> Alex
>