Re: [PATCH 2/2] gpio: realtek-otto: decide bank_read/write by device endianness

[Bartosz Golaszewski]

On Wed, 15 Jul 2026 21:00:45 +0200, Rustam Adilov <adilov@xxxxxxxxxxx> said:
> Hello,
> On 2026-07-15 09:39, Bartosz Golaszewski wrote:
>> On Fri, 10 Jul 2026 20:34:39 +0200, Rustam Adilov <adilov@xxxxxxxxxxx> said:
>>> In order to have a working gpio controller with SWAP_IO_SPACE,
>>> the way bank_read and bank_write are defined must be changed and
>>> separated from GPIO_PORTS_REVERSED flag. That also includes the
>>> flags parameter used by gpio_generic_chip_config.
>>>
>>> To achieve it, use the device_is_big_endian() to decide the
>>> bank_read/write parameter and the flag.
>>>
>>> Signed-off-by: Rustam Adilov <adilov@xxxxxxxxxxx>
>>> ---
>>>  drivers/gpio/gpio-realtek-otto.c | 15 +++++++++------
>>>  1 file changed, 9 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpio/gpio-realtek-otto.c b/drivers/gpio/gpio-realtek-otto.c
>>> index 491fde846d46..f96072fbce92 100644
>>> --- a/drivers/gpio/gpio-realtek-otto.c
>>> +++ b/drivers/gpio/gpio-realtek-otto.c
>>> @@ -393,16 +393,19 @@ static int realtek_gpio_probe(struct platform_device *pdev)
>>>
>>>  	raw_spin_lock_init(&ctrl->lock);
>>>
>>> -	if (dev_flags & GPIO_PORTS_REVERSED) {
>>> -		gen_gc_flags = 0;
>>> -		ctrl->bank_read = realtek_gpio_bank_read;
>>> -		ctrl->bank_write = realtek_gpio_bank_write;
>>> +	if (dev_flags & GPIO_PORTS_REVERSED)
>>>  		ctrl->line_imr_pos = realtek_gpio_line_imr_pos;
>>> -	} else {
>>> +	else
>>> +		ctrl->line_imr_pos = realtek_gpio_line_imr_pos_swapped;
>>> +
>>> +	if (device_is_big_endian(dev)) {
>>>  		gen_gc_flags = GPIO_GENERIC_BIG_ENDIAN_BYTE_ORDER;
>>>  		ctrl->bank_read = realtek_gpio_bank_read_swapped;
>>>  		ctrl->bank_write = realtek_gpio_bank_write_swapped;
>>> -		ctrl->line_imr_pos = realtek_gpio_line_imr_pos_swapped;
>>> +	} else {
>>> +		gen_gc_flags = 0;
>>> +		ctrl->bank_read = realtek_gpio_bank_read;
>>> +		ctrl->bank_write = realtek_gpio_bank_write;
>>>  	}
>>>
>>>  	config = (struct gpio_generic_chip_config) {
>>> --
>>> 2.55.0
>>>
>>>
>>
>> Can you look at the sashiko report? I think it's right about this change
>> possibly breaking existing devicetrees. Can we keep big-endian as the
>> default?
>>
>> Bart
>
> Oh i didn't know sashiko was looking after this subsystem too.
> But yes, it does require the rtl8380-gpio, rtl8390-gpio, rtl9310-gpio
> to append big-endian or native-endian (as they are all big endian chips).
>
> I was thinking earlier whatever it is appropriate to make changes to
> the arch/mips/boot/dts/realtek in this commit because it is different
> subsystem entirely but i guess this (previous sentence) answers the
> question, doesn't it.
>

That's irrelevant as there may be devicetrees out in the wild and we can't
just break them.

> Also, what exactly do you mean by "Can we keep big-endian as the
> default?" ? My only reading off is to change the if statement
> so that the big endian flag and the _swapped functions to be
> under the else part, is it correct?
>

Yes, just retain the original default behavior.

Bart