Re: [PATCH 0/2] gpio: 74x164: use a compatible fallback and don't extend the driver

[Krzysztof Kozlowski <krzk@kernel.org>]

On 10/01/2025 15:14, Bartosz Golaszewski wrote:
>> At24 EEPROMs differ from '595 shift registers in that they provide an
>> API with multiple commands, and some commands or parameter bits may
>> differ among different implementations (but usually these differences
>> are called quirks).
>>
>> All '595 (I'm deliberately writing it like that) shift registers
>> should be 100% compatible, modulo some electrical specifications
>> (voltage levels, maximum speed, power consumption, ...).
>>
>> Interestingly, the driver is called gpio-74x164.c, while no '164
>> compatible value is present. Most important difference is that the
>> '164 lacks the output latch, which is used as chip-select with SPI[1].
>>
>>>> I'm especially against introducing a new, vendor-specific (On Semi, in
>>>> this case) name; if we really want to introduce a new compatible, at
>>>> least make it as generic as possible, i.e. `generic,74x595`, or even
>>>> `generic,spi-shift-register-output`.
>>>
>>> If anything, that would have to be the fallback that the driver knows.
>>> The first string in the compatible property has to have an actual
>>> vendor (I think, I'll let DT maintainers correct me).
>>
>> For the inverse operation (parallel in, serial out), there's just
>> "pisosr-gpio".
>>
> 
> Ok, I admit I don't know the correct next step. I'll wait for
> Krzysztof, Rob or Conor to chime in (on the subject of representing
> reality - the actual manufacturer - in DTS) and then possibly just
> remove patches 1-2 from my tree.
> 

Well, folks, I don't know the exact device, so maybe there is no point
in a new compatible if there is a claim all devices have same interface
and documenting all of them would result in 1000 redundant
compatibles... but OTOH, that's what we still do with jedec,spi and
at24, so if we can add specific compatibles for these, we can do same
also here.

Best regards,
Krzysztof