linux-kernel - Re: [PATCH 4/9] gpio: regmap: add the .get

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Message-ID: <0d0e9cee-2aaa-402d-a811-8c4704aadd74@lunn.ch>
Date: Wed, 9 Jul 2025 17:09:17 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Ioana Ciornei <ioana.ciornei@....com>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Shawn Guo <shawnguo@...nel.org>, Michael Walle <mwalle@...nel.org>,
	Lee Jones <lee@...nel.org>, Frank Li <Frank.Li@....com>
Subject: Re: [PATCH 4/9] gpio: regmap: add the .get_direction() callback

On Wed, Jul 09, 2025 at 02:26:53PM +0300, Ioana Ciornei wrote:
> There are GPIO controllers such as the one present in the LX2160ARDB
> QIXIS CPLD which are single register fixed-direction. This cannot be
> modeled using the gpio-regmap as-is since there is no way to
> present the true direction of a GPIO line.
> 
> In order to make this use case possible, add a new callback to the
> gpio_config structure - .get_direction() - which can be used by user
> drivers to provide the fixed direction per GPIO line.
> 
> Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
> ---
>  drivers/gpio/gpio-regmap.c  | 17 ++++++++++++++++-
>  include/linux/gpio/regmap.h |  3 +++
>  2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> index 87c4225784cf..dac2acb26655 100644
> --- a/drivers/gpio/gpio-regmap.c
> +++ b/drivers/gpio/gpio-regmap.c
> @@ -32,6 +32,8 @@ struct gpio_regmap {
>  	unsigned int reg_dir_in_base;
>  	unsigned int reg_dir_out_base;
>  
> +	int (*get_direction)(struct gpio_regmap *gpio, unsigned int offset);
> +

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. Is it the current direction, or the supported
directions? Maybe it should be called get_fixed_direction()?

I then wounder how it will be implemented. Since it is fixed, it is
probably just a constant bitmap, and you look at the offset bit in
this batmap? At minimum a ready made helper could be provided, or
rather than have this op, just provide the bitmap, and gpio-regmap.c
can look at the bit in the bitmap?

	Andrew