linux-kernel - Re: [PATCH RFT 2/6] gpio: mmio: get chip label and GPIO base from device properties

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Message-ID: <b9c6f5bf-ac43-497a-9354-6448cfb2839c@kernel.org>
Date: Wed, 25 Jun 2025 12:26:21 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
 Linus Walleij <linus.walleij@...aro.org>, Lee Jones <lee@...nel.org>,
 Liviu Dudau <liviu.dudau@....com>, Sudeep Holla <sudeep.holla@....com>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Aaro Koskinen <aaro.koskinen@....fi>,
 Janusz Krzysztofik <jmkrzyszt@...il.com>, Tony Lindgren <tony@...mide.com>,
 Russell King <linux@...linux.org.uk>, Alim Akhtar <alim.akhtar@...sung.com>,
 linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
 patches@...nsource.cirrus.com, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH RFT 2/6] gpio: mmio: get chip label and GPIO base from
 device properties

On 25/06/2025 12:23, Bartosz Golaszewski wrote:
> On Wed, Jun 25, 2025 at 10:54 AM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>>
>> On 25/06/2025 09:35, Bartosz Golaszewski wrote:
>>> On Tue, 24 Jun 2025 at 21:44, Linus Walleij <linus.walleij@...aro.org> wrote:
>>>>
>>>> On Tue, Jun 24, 2025 at 3:19 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>>>>
>>>>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>>>
>>>>> Ahead of removing struct bgpio_pdata support from the gpio-mmio generic
>>>>> module, let's add support for getting the relevant values from generic
>>>>> device properties. "label" is a semi-standardized property in some GPIO
>>>>> drivers so let's go with it. There's no standard "base" property, so
>>>>> let's use the name "gpio-mmio,base" to tie it to this driver
>>>>> specifically. The number of GPIOs will be retrieved using
>>>>> gpiochip_get_ngpios() so there's no need to look it up in the software
>>>>> node.
>>>>>
>>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>>
>>>> This works for me.
>>>> I wouldn't be stoked to see device trees abusing the "gpio-mmio,base"
>>>> property all of a sudden just because it now exists as a device
>>>> property though... I kind of wish we had a way to opt out of exposing
>>>> this to all the sub-property paths. But it seems tiresome, so:
>>>>
>>>> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
>>>>
>>>> Yours,
>>>> Linus Walleij
>>>
>>> That's not a problem - this property is not in any DT bindings and as
>>> such is not an allowed property in DT sources. For out-of-tree DTs? We
>>> don't care about those.
>> That's not true, we do care about implied ABI. Try changing/breaking
>> this later, when users complain their out of tree DTS is affected, and
>> explaining this all to Greg.
>>
> 
> Wait, seriously? I thought that the upstream bindings are the source
> of truth for device-tree sources...


They are, until they are not... ok, we don't really care that much about
out of tree DTS, but in-tree DTS still could use these and don't care
about bindings check, right?

Best regards,
Krzysztof