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

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Message-Id: <20250917090422.870033-6-ioana.ciornei@nxp.com>
Date: Wed, 17 Sep 2025 12:04:17 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: 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>,
	devicetree@...r.kernel.org,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Frank Li <Frank.Li@....com>
Subject: [PATCH v3 05/10] gpio: regmap: add the .fixed_direction_output configuration parameter

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);
+		if (!gpio->fixed_direction_output)
+			return ERR_PTR(-ENOMEM);
+		bitmap_copy(gpio->fixed_direction_output,
+			    config->fixed_direction_output, chip->ngpio);
+	}
+
 	/* if not set, assume there is only one register */
 	gpio->ngpio_per_reg = config->ngpio_per_reg;
 	if (!gpio->ngpio_per_reg)
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index c722c67668c6..8d3d595bfdd3 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -37,6 +37,10 @@ struct regmap;
  *			offset to a register/bitmask pair. If not
  *			given the default gpio_regmap_simple_xlate()
  *			is used.
+ * @fixed_direction_output:
+ *			(Optional) Bitmap representing the fixed direction of
+ *			the GPIO lines. Useful when there are GPIO lines with a
+ *			fixed direction mixed together in the same register.
  * @drvdata:		(Optional) Pointer to driver specific data which is
  *			not used by gpio-remap but is provided "as is" to the
  *			driver callback(s).
@@ -78,6 +82,8 @@ struct gpio_regmap_config {
 	int ngpio_per_reg;
 	struct irq_domain *irq_domain;
 
+	unsigned long *fixed_direction_output;
+
 	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
 			      unsigned int offset, unsigned int *reg,
 			      unsigned int *mask);
-- 
2.25.1