Re: [PATCH 1/4] dt-bindings: nvmem: new optional property write-protect-gpios

[Bartosz Golaszewski <bgolaszewski@baylibre.com>]

pt., 22 lis 2019 o 13:53 Linus Walleij <linus.walleij@linaro.org> napisał(a):
>
> On Fri, Nov 22, 2019 at 1:47 PM Bartosz Golaszewski
> <bgolaszewski@baylibre.com> wrote:
>
> > what about the existing bindings for at24 that don't mandate the
> > active-low flag? I'm afraid this would break the support for this
> > specific chip or lead to code duplication if we had this in both nvmem
> > and at24 with different logic.
>
> Hm yeah I realized this when I read patches 3 & 4.
>
> I would to like this:
>
> 1. Add a new generic property
>    writeprotect-gpios that mandates to use GPIO_ACTIVE_LOW
>    and use this in the new example
>
> 2. Deprecate wp-gpios in the binding, keep it around but deprecated.

This is a pretty standard property though - for instance it is
documented in the main mmc binding and doesn't mandate GPIO_ACTIVE_LOW
either. I think this is because nobody says that the write-protect
line must always be driver low to be asserted - this is highly
implementation-specific.

Bartosz

>
> 3. Add a quirk to gpiolib-of in the manner of the other quirks there
>    (like for SPI) so that if we are dealing with some EEPROM node
>    like at24 and the flag is zero, tag on GPIO_ACTIVE_LOW on
>    the descriptor.
>
> The driver will now handle the semantic of both cases
> with gpiolib-of providing a quirk for the old binding.
>
> This is how we solved this type of problem before.
>
> Yours,
> Linus Walleij