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

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Message-ID: <CACRpkdaW82pgQivc0VVgqqVv4fgXxMyGD3Lo8YHcMK7aGPDKaw@mail.gmail.com>
Date:   Fri, 22 Nov 2019 13:53:07 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Khouloud Touil <ktouil@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        baylibre-upstreaming@...ups.io,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, linux-i2c <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH 1/4] dt-bindings: nvmem: new optional property write-protect-gpios

On Fri, Nov 22, 2019 at 1:47 PM Bartosz Golaszewski
<bgolaszewski@...libre.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.

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