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

[Rustam Adilov <adilov@disroot.org>]

Hello,
On 2026-07-15 09:39, Bartosz Golaszewski wrote:
> On Fri, 10 Jul 2026 20:34:39 +0200, Rustam Adilov <adilov@disroot.org> 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@disroot.org>
>> ---
>>  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.

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?

Best,
Rustam