Re: [RFC PATCH 00/16] OMAP: GPMC: Restructure OMAP GPMC driver (NAND) : DT binding change proposal

Roger Quadros
2014-05-26T07:34:52Z

On 05/23/2014 05:53 PM, Tony Lindgren wrote:
> * Roger Quadros <rogerq@ti.com> [140523 01:17]:
>> On 05/22/2014 05:46 PM, Ezequiel Garcia wrote:
>>> On 22 May 01:51 PM, Javier Martinez Canillas wrote:
>>>> On Thu, May 22, 2014 at 10:12 AM, Roger Quadros <rogerq@ti.com> wrote:
>>>>>> On 21 May 02:20 PM, Roger Quadros wrote:
>>>>>> While I agree that the GPMC driver is a bit messy, I'm not sure it's possible
>>>>>> to go through such a complete devicetree binding re-design (breaking backwards
>>>>>> compatibility) now that the binding is already in production.
>>>>>
>>>>> Why not? especially if the existing bindings are poorly dones. Is anyone using these
>>>>> bindings burning the DT into ROM and can't change it when they update the kernel?
>>>>>
>>>>
>>>> While I do agree that your DT bindings are much better than the
>>>> current ones, there is a policy that DT bindings are an external API
>>>> and once are released with a kernel are set in stone and can't be
>>>> changed.
>>>>
>>>
>>> Exactly. The DT binding is considered an ABI. Thus, invariant across kernel
>>> versions. Users can't be coherced into a DTB update after a kernel update.
>>>
>>> That said, I don't really care if you break compatilibity in this case.
>>> Rather, I'm suggesting that you make sure this change is going to be accepted
>>> upstream, before doing any more work. The DT maintainers are reluctant to do
>>> so.
>>
>> Appreciate your concern.
>>
>> Would be really nice if you can review patches 1-12. They have nothing to do with DT changes.
>> Thanks.
>
> I'm mostly concerned about keeping things working. I think the
> only way we can keep things working is to keep support for
> the old binding around in addition to the new one. That way
> we can update devices one at a time.

Good to hear that you are not keen on keeping the old bindings forever. I understand
that we need to keep things working during the transition. I'll think of something to
maintain backward compatibility while supporting the new binding.

cheers,
-roger