[RFC] drm/bridge: megachips-stdpxxxx-ge-b850v3-fw: switch to drm_do_get_edid()

[Peter Senna Tschudin]

Good morning Jani,

It has been a long time since I wrote the driver, and many many years
since I sent my last kernel patch, so my memory does not serve me very
well, but I will try to shed some light.

On Fri, Sep 1, 2023 at 12:24 PM Jani Nikula <jani.nikula at intel.com> wrote:
>
> The driver was originally added in commit fcfa0ddc18ed ("drm/bridge:
> Drivers for megachips-stdpxxxx-ge-b850v3-fw (LVDS-DP++)"). I tried to
> look up the discussion, but didn't find anyone questioning the EDID
> reading part.
>
> Why does it not use drm_get_edid() or drm_do_get_edid()?
>
> I don't know where client->addr comes from, so I guess it could be
> different from DDC_ADDR, rendering drm_get_edid() unusable.
>
> There's also the comment:
>
>         /* Yes, read the entire buffer, and do not skip the first
>          * EDID_LENGTH bytes.
>          */
>
> But again, there's not a word on *why*.

The video pipeline has two hardware bridges between the LVDS from the
SoC and DP+ output. For reasons, we would get hot plug events from one
of these bridges, and EDID from the other. If I am not mistaken, I
documented this strangeness in the DTS readme file.

Did this shed any light on the *why* or did I tell you something you
already knew?