Re: [PATCH 1/4] gpiolib: add opt-out for existing drivers with static GPIO base

[Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>]

On 14.01.25 20:38, Andy Shevchenko wrote:
> On Tue, Jan 14, 2025 at 12:06 PM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote:
>> On 14.01.25 10:49, Andy Shevchenko wrote:
>>> On Tue, Jan 14, 2025 at 12:20 AM Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> wrote:
>>>>
>>>> Some drivers have had deterministic GPIO numbering for most of
>>>> their existence, e.g. the i.MX GPIO since commit 7e6086d9e54a
>>>> ("gpio/mxc: specify gpio base for device tree probe"), more than
>>>> 12 years ago.
>>>>
>>>> Reverting this to dynamically numbered will break existing setups in
>>>> the worst manner possible: The build will succeed, the kernel will not
>>>> print warnings, but users will find their devices essentially toggling
>>>> GPIOs at random with the potential of permanent damage.
>>>>
>>>> As these concerns won't go away until the sysfs interface is removed,
>>>> let's add a new struct gpio_chip::legacy_static_base member that can be
>>>> used by existing drivers that have been grandfathered in to suppress
>>>> the warning currently being printed:
>>>>
>>>>   gpio gpiochip0: Static allocation of GPIO base is deprecated,
>>>>   use dynamic allocation.
>>>
>>> Warning is harmless and still a good reminder for the stuff that needs
>>> more love.
>>> NAK.
>>
>> A warning is a call-to-action and it's counterproductive to keep tricking
>> people into removing the static base and breaking other users' scripts.
> 
> Are you prepared to say the same when the entire GPIO SYSFS will be
> removed? Because that's exactly what I referred to in the reply to the
> cover letter as an impediment to move forward.

No. But this gives me an idea: We could make the warning dependent
on CONFIG_GPIO_SYSFS and add a comment to the i.MX code suggesting
users do that instead. What do you think?

>> I don't understand what love you think this will spawn with regards
>> to the i.MX GPIO driver. Can you explain?
> 
> To fix the bugs you found. If it's not the GPIO driver a culprit, we
> need to find the real one and fix that.

Again: jumbling GPIOs with potential hardware harm as a result is not a fix.

Cheers,
Ahmad


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