Re: [PATCH RFC 0/2] pinctrl: Add support gpiod_to_irq

[Xianwei Zhao <xianwei.zhao@amlogic.com>]

Hi Linus,
    Understood. Thank you for your detailed explanation. I will drop 
this patch.

On 2026/6/15 20:59, Linus Walleij wrote:
>>> Hi Xianwei,
>>>
>>> thanks for your patches!
>>>
>>> On Thu, Jun 11, 2026 at 9:54 AM Xianwei Zhao via B4 Relay
>>> <devnull+xianwei.zhao.amlogic.com@kernel.org>   wrote:
>>>
>>>> Some users need to obtain an IRQ directly from a GPIO descriptor through gpiod_to_irq().
>>>> Add the required DT binding and implementation to support this use case.
>>>> Since this introduces a new DT property, the property is kept optional to
>>>> maintain compatibility with existing SoCs and DTS files.
>>> To me it looks like you have just re-implemented hierarchical
>>> irqs.
>>>
>>> Look into the section "Infrastructure helpers for GPIO irqchips"
>>> in Documentation/driver-api/gpio/driver.rst, especially towards
>>> the end.
>>>
>>> Solve this by using GPIOLIB_IRQCHIP and a custom
>>> child_to_parent_hwirq() callback to translate the GPIO into
>>> an IRQ.
>>>
>>> To just implement gpiod_to_irq() without any irqchip abstraction
>>> is also broken: you can't force all users to just use this way
>>> to get an IRQ it's excessively restricting.
>>>
>>> Add
>>>
>>>     interrupt-controller: true
>>>
>>>     "#interrupt-cells":
>>>       const: 2
>>>
>>> to the pinctrl node as well so that DT users can simply request
>>> the IRQ from the irqchip inside of the pin controller. It will
>>> be hierarchical and lightweight but an irqchip nevertheless.
>>>
>>> The GPIOLIB_IRQCHIP approach will help you to get this
>>> right.
>>>
>> I read the document (Documentation/driver-api/gpio/driver.rst) you
>> pointed me to and found that the corresponding implementation has
>> already been added in this file:
>>
>> https://github.com/torvalds/linux/blob/master/drivers/irqchip/irq-meson-gpio.c
> That is the parent interrupt controller to the pinctrl+gpio isn't it.
> 
> It will be even clearer once you use interrupts = <>; instead of
> the hwirq = <>; hack.
> 
>> However, it is implemented as a standalone irqchip and is not integrated
>> with the GPIO controller.
> Right, so it is the parent. Of course it it stand alone.
> 
>> In this patch, I implemented the GPIO-to-IRQ conversion through
>> gpiod_to_irq(). Users can still obtain the interrupt directly through
>> the interrupt property, for example:
>>
>> interrupts-extended = <&gpio_intc 16 1>;
>>
>> The purpose of this change is to make GPIO-to-IRQ conversion easier for
>> users who do not want to know the actual interrupt number. The interrupt
>> mapping is not fixed and varies between different SoCs, so users should
>> not need to handle the hardware interrupt allocation details.
> This is not why gpiod_to_irq() exists. It is not a convenience function
> that is voluntary to implement.
> 
> If you implement gpiod_to_irq() you implement an entire
> irqchip otherwise it is a bug.
> 
> If the pin control + GPIO driver should serve IRQ numbers in any
> shape or form, you need to go the whole way and provide a
> hierarchical irqchip.
> 
> It doesn't matter if you don't need to set a single bit in the
> pinctrl + GPIO hardware for these IRQs, the fact that they are
> routed internally on the SoC out through the pin control and
> GPIO block by definition makes it hierarchical.
> 
> Yours,
> Linus Walleij