On Tue, 2 Dec 2025 13:51:59 +0200
Tomi Valkeinen [off-list ref] wrote:

Hi Kory,

On 02/12/2025 13:18, Kory Maincent wrote:

quoted

On Tue, 2 Dec 2025 11:47:40 +0100
Krzysztof Kozlowski [off-list ref] wrote:

I will not NAK, removing bindings and breaking users is under some
conditions acceptable. You just need to come with the reasons and impact.

Reason "is ugly" is usually not good enough. Especially if things were
working.

Thanks for you reply.

quoted

quoted

DTS cannot go to drm, which means you either need to separate the change
and make entire work bisectable and backwards compatible for some time
OR at least document clearly the impact as we always ask.  

The thing is, if I split it, it has to be in 3. One for the of DRM bus flags
support, a second for the the devicetree and binding change and a third for
the whole tilcdc and tda998x cleaning stuff. I think I will go for one
series, with better documentation.

Now, what is your point of view on my question. Will you nak any binding
removal even if the binding is ugly and legacy and imply maintaining an
non-standard tilcdc panel driver? I know it breaks DTB compatibility but
there is several argument to not keep it. See patch 6.  

The binding being ugly and having to maintain non-standard tilcdc panel
driver may be nice things for us, the users don't care. The users care
if their board no longer works.

Yes I understand but then I have another question. At what cost should we
continue to support legacy binding?

Just figured out this case already happened, ti,tilcdc,slave binding was
removed from the tilcdc driver:
739acd85ffdb7 ("drm/tilcdc: Remove obsolete "ti,tilcdc,slave" dts binding
support")

Even if there is still one mainline device tree that uses it:
am335x-base0033.dts. :/

And how does this sync with u-boot? It also has code for at least for a
few of these boards.

U-boot has indeed a driver for the ti,tilcdc,panel binding.
Changing this devicetree would beak display for these board in U-boot as it
currently does not support the "panel-dpi" binding.

Are there even users for these boards? If not, maybe they can be just
removed? I'm personally not familiar with these boards, so I have no
idea of their age or distribution.

These boards are quite old (>10 years) but I don't know if they are still used
by people. After a quick look they seem not available on the market.

One trick that can be done is to modify the loaded DTB at boot time,
detecting the old format, converting it to the new one, so that when the
drivers are probed they only see the new DTB.

Yes, indeed that could do the trick. The things is, I don't have one of
theses board to test it. I will try to look for an other way to test it.

Regards,
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com