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

Roger Quadros
2014-05-23T08:17:17Z

Ezequiel & Javier,

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:
>>>>>
>>>>> For DT boot:
>>>>> - The GPMC controller node should have a chip select (CS) node for each used
>>>>> chip select. The CS node must have a child device node for each device
>>>>> attached to that chip select. Properties for that child are GPMC agnostic.
>>>>>
>>>>> i.e.
>>>>> gpmc {
>>>>> cs0 {
>>>>> nand0 {
>>>>> }
>>>>> };
>>>>>
>>>>> cs1 {
>>>>> nor0 {
>>>>> }
>>>>> }
>>>>> ...
>>>>> };
>>>>>
>>>>
>>>> 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.

cheers,
-roger

>
> On the other side, I guess you will also break bisectability while breaking
> backward compatibility. Doesn't sound very nice.
>