linux-kernel - Re: [PATCH v3 05/10] gpio: regmap: add the .fixed_direction

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Message-ID: <7xzabghtgro7wv4mbx7zywm5tnquttthdzrc2duiwvejm4knn7@b4fp7u6jmaia>
Date: Thu, 18 Sep 2025 18:45:24 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Frank Li <Frank.Li@....com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Linus Walleij <linus.walleij@...aro.org>, Shawn Guo <shawnguo@...nel.org>, 
	Michael Walle <mwalle@...nel.org>, Lee Jones <lee@...nel.org>, devicetree@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/10] gpio: regmap: add the .fixed_direction_output
 configuration parameter

On Thu, Sep 18, 2025 at 03:55:16AM -0700, Bartosz Golaszewski wrote:
> On Wed, 17 Sep 2025 11:04:17 +0200, Ioana Ciornei <ioana.ciornei@....com> said:
> > There are GPIO controllers such as the one present in the LX2160ARDB
> > QIXIS FPGA which have fixed-direction input and output GPIO lines mixed
> > together in a single register. 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 configuration
> > parameter - fixed_direction_output - into the gpio_regmap_config
> > structure. This will enable user drivers to provide a bitmap that
> > represents the fixed direction of the GPIO lines.
> >
> > Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
> > ---
> > Changes in v2:
> > - Add the fixed_direction_output bitmap to the gpio_regmap_config
> > Changes in v3:
> > - Make a deep copy of the new bitmap.
> > - Remove the offset check against the ngpio.
> > - Added documentation for the new config field.
> >
> >  drivers/gpio/gpio-regmap.c  | 18 ++++++++++++++++++
> >  include/linux/gpio/regmap.h |  6 ++++++
> >  2 files changed, 24 insertions(+)
> >
> > diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> > index e8a32dfebdcb..9edd79b5c10e 100644
> > --- a/drivers/gpio/gpio-regmap.c
> > +++ b/drivers/gpio/gpio-regmap.c
> > @@ -31,6 +31,7 @@ struct gpio_regmap {
> >  	unsigned int reg_clr_base;
> >  	unsigned int reg_dir_in_base;
> >  	unsigned int reg_dir_out_base;
> > +	unsigned long *fixed_direction_output;
> >
> >  	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
> >  			      unsigned int offset, unsigned int *reg,
> > @@ -129,6 +130,13 @@ static int gpio_regmap_get_direction(struct gpio_chip *chip,
> >  	unsigned int base, val, reg, mask;
> >  	int invert, ret;
> >
> > +	if (gpio->fixed_direction_output) {
> > +		if (test_bit(offset, gpio->fixed_direction_output))
> > +			return GPIO_LINE_DIRECTION_OUT;
> > +		else
> > +			return GPIO_LINE_DIRECTION_IN;
> > +	}
> > +
> >  	if (gpio->reg_dat_base && !gpio->reg_set_base)
> >  		return GPIO_LINE_DIRECTION_IN;
> >  	if (gpio->reg_set_base && !gpio->reg_dat_base)
> > @@ -277,6 +285,16 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
> >  			return ERR_PTR(ret);
> >  	}
> >
> > +	if (config->fixed_direction_output) {
> > +		gpio->fixed_direction_output = devm_bitmap_alloc(config->parent,
> > +								 chip->ngpio,
> > +								 GFP_KERNEL);
> 
> Please don't use devres hidden in what is effectively a library function for
> drivers. You have no guarantee this will always be used in probe or that the
> life-time of this will end with the associated device's detach. Just use
> a regular bitmap_alloc().

Ok, sure. I will switch to bitmap_alloc() and bitmap_free().

Ioana