On Fri Jul 11, 2025 at 8:06 PM CEST, Linus Walleij wrote:

On Fri, Jul 11, 2025 at 7:45 PM Andrew Lunn [off-list ref] wrote:

quoted

On Fri, Jul 11, 2025 at 07:43:13PM +0200, Linus Walleij wrote:

quoted

On Wed, Jul 9, 2025 at 5:09 PM Andrew Lunn [off-list ref] wrote:

quoted

This is not my area, so i will deffer to the GPIO
Maintainers. However, it is not clear to me what get_direction()
should return.

This callback should return the current direction as set up
in the hardware.

A major usecase is that this is called when the gpiochip is
registered to read out all the current directions of the GPIO
lines, so the kernel has a clear idea of the state of the
hardware.

Calling this should ideally result in a read of the status from
a hardware register.

O.K, so completely different to what is proposed in this patch.

Maybe you can suggest a better name.

If the hardware only supports one direction, then .get_direction()
should return that direction.

What the patch does is to
read the direction from the hardware and use that in the
set_direction() callback, as if all regmapped hardware in the
world had fixed direction, that's wrong.

I'd just add something custom in gpio-regmap if this is
something reoccuring in regmapped GPIO drivers.

bool is_fixed_direction(struct gpio_regmap *gpio, unsigned int offset)

or so?

Then the core can use is_fixed_direction() together
with gpio_get_direction() to check if it can do
a certain set_direction().

Pseudocode:

mydir = get_direction(line)
if (is_fixed_direction(line) && (mydir != requested_dir)
  return -ERROR;

You don't need a .is_fixed_direction(). You can deduce that if only
.get_direction() is set in the gpio-regmap config.

mydir = get_direction(line)
if (!config->set_direction && mydir != requested_dir)
  return -ERROR;

That or either Andrew's idea of setting a bitmap within the
gpio-regmap config which already tells the gpio-regmap core and then
amend gpio_regmap_get_direction() to return that fixed direction if
that bitmap is not NULL.

I'm fine with both.

-michael