[PATCH v6 4/9] gpio: regmap: add the .fixed_direction_output configuration parameter

Ioana Ciornei
2025-10-14T15:54:31Z

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@nxp.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Michael Walle <mwalle@kernel.org>
---
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.
Changes in v4:
- Replace devres bitmap allocation with bitmap_alloc() and
bitmap_free().
Changes in v5:
- Rebased on top of latest linux-next, change the extra goto statement.
Changes in v6:
- none

drivers/gpio/gpio-regmap.c | 26 ++++++++++++++++++++++++--
include/linux/gpio/regmap.h | 5 +++++
2 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index ab9e4077fa60..f4267af00027 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;

#ifdef CONFIG_REGMAP_IRQ
int regmap_irq_line;
@@ -134,6 +135,13 @@ 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)
@@ -284,6 +292,17 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
goto err_free_gpio;
}

+ if (config->fixed_direction_output) {
+ gpio->fixed_direction_output = bitmap_alloc(chip->ngpio,
+ GFP_KERNEL);
+ if (!gpio->fixed_direction_output) {
+ ret = -ENOMEM;
+ goto err_free_gpio;
+ }
+ 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)
@@ -300,7 +319,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config

ret = gpiochip_add_data(chip, gpio);
if (ret < 0)
- goto err_free_gpio;
+ goto err_free_bitmap;

#ifdef CONFIG_REGMAP_IRQ
if (config->regmap_irq_chip) {
@@ -309,7 +328,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
config->regmap_irq_line, config->regmap_irq_flags,
0, config->regmap_irq_chip, &gpio->irq_chip_data);
if (ret)
- goto err_free_gpio;
+ goto err_free_bitmap;

irq_domain = regmap_irq_get_domain(gpio->irq_chip_data);
} else
@@ -326,6 +345,8 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config

err_remove_gpiochip:
gpiochip_remove(chip);
+err_free_bitmap:
+ bitmap_free(gpio->fixed_direction_output);
err_free_gpio:
kfree(gpio);
return ERR_PTR(ret);
@@ -344,6 +365,7 @@ void gpio_regmap_unregister(struct gpio_regmap *gpio)
#endif

gpiochip_remove(&gpio->gpio_chip);
+ bitmap_free(gpio->fixed_direction_output);
kfree(gpio);
}
EXPORT_SYMBOL_GPL(gpio_regmap_unregister);
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index 622a2939ebe0..87983a5f3681 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -38,6 +38,10 @@ 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).
@@ -85,6 +89,7 @@ struct gpio_regmap_config {
int reg_stride;
int ngpio_per_reg;
struct irq_domain *irq_domain;
+ unsigned long *fixed_direction_output;

#ifdef CONFIG_REGMAP_IRQ
struct regmap_irq_chip *regmap_irq_chip;
--
2.25.1