Re: [PATCH v2 2/3] drm/edid: Add drm_edid_get_preferred_size()

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 31 Aug 2026, Thomas Zimmermann <tzimmermann@suse.de> wrote:
> Hi
>
> Am 31.08.26 um 15:13 schrieb Jani Nikula:
>> On Mon, 31 Aug 2026, Thomas Zimmermann <tzimmermann@suse.de> wrote:
>>> +
>>> +	/*
>>> +	 * Use display mode from the Preferred Timing Descriptor. For old
>>> +	 * and obscure displays, we might need better heuristics.
>>> +	 */
>>> +
>>> +	if (edid->revision < 4 && !(edid->features & DRM_EDID_FEATURE_PREFERRED_TIMING))
>> The preferred timing mode should always be there starting from EDID
>> 1.3. The bit doesn't indicate whether it's there or not. It should be
>> always set for EDID 1.3, and for EDID 1.4 it indicates whether the
>> preferred timing includes the native pixel format and the preferred
>> refresh rate.
>>
>> I think just if (edid->revision < 3) should be enough.
>
> Ok

I think I may have gotten this one wrong, and your original was correct.

I didn't double check what the EDID spec definition of pixel format is:
"Native Pixel Format is defined as the number of physical pixels along
the horizontal axis by the number of physical pixels along the vertical
axis of the display device."

i.e. exactly what you're looking for. Usually, I would not consider
"pixel format" to include resolution.

The preferred timing will still be there as I described, and I would
*guess* preferred most likely equals native, but your original is the
more cautious approach.

My bad, sorry for the noise.


BR,
Jani.


-- 
Jani Nikula, Intel