[PATCH 12/18] drm/sysfb: ofdrm: Add EDID support

[Thomas Zimmermann]

Hi

Am 31.03.25 um 11:26 schrieb Maxime Ripard:
> On Thu, Mar 20, 2025 at 02:08:56PM +0100, Thomas Zimmermann wrote:
>>> Despite the nitpicks, overall LGTM.
>> Thanks for reviewing.
>>
>> Since I have your attention and you're knowledgeable wrt EDID: byte 20 of
>> the EDID header indicates the type of output (analog, HDMI, DP, etc). I
>> intent to use this for setting the connector type to something better then
>> UNKNOWN. Does that make sense?
> I don't think it would work:
>
>    - EDID doesn't indicate the kind of KMS output (ie, source) but the
>      type of sink. Ie, what the monitor is capable of dealing with, not
>      what the connector can emit. If we have (passive or active) bridges
>      in between, it does mean that we can have an analog sink connected
>      to a digital connector.
>
>    - Since it depends on the sink, it can change over time, ie you plug
>      an analog monitor, remove it, and plug a digital one. That would
>      mean changing the connector type (and thus name exposed to
>      userspace) at runtime, for the same driver.
>
>    - Since it depends on the sink, it assumes the sink vendor didn't
>      botch the EDID. This one is a pretty big if :)

I see. I'd really just want this for these sysfb outputs that come from 
the firmware. They should not change much at runtime.  Right now, the 
connector is always UNKNOWN and giving some type would indicate to the 
user which display is in use. But it's not really so important.

Best regards
Thomas

>
> Maxime

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
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