Re: [PATCH 01/24] Documentation: DT: document compatible string existence requirement

Rob Herring
2015-01-29T18:16:14Z

On Thu, Jan 29, 2015 at 10:43 AM, Javier Martinez Canillas
<javier.martinez@collabora.co.uk> wrote:
> Hello Paul,
>
> On 01/29/2015 12:49 AM, Paul Walmsley wrote:
>>
>> DT maintainers require all compatible strings used in chip or board
>> DTS file to be previously documented somewhere in
>> Documentation/devicetree/bindings, per:
>>
>> http://marc.info/?l=linux-tegra&m=142201349727836&w=2
>>
>
> I would had preferred if checkpatch.pl didn't warn about the most specific
> variants of the IP blocks tbh.

Patches welcome.

It would be hard because in cases where there are generic strings, we
always need to have a specific one.

> Since afaiu those were only added to the compatible string as a way to make
> it future proof in case there is going to be needed later. So in that sense
> I thought they were not part of the DT ABI.
>
> Now, dumping the unused specific strings in binding docs only to make
> checkpatch happy, will have the effect of making those unused strings become
> part of the DT ABI. Which mean that couldn't be dropped later if those are
> found to not be needed since there won't be a way to know if an OS following
> the DT binding will be matching those or not.

If they are in the DTS, then they are effectively already part of the ABI.

You have some wiggle room if they are known not to be used whether
they are documented or not. You can never prove they are not needed in
the future to be able to drop them.

Rob