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>
---
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);
--
2.25.1On Wed, 17 Sep 2025 11:04:17 +0200, Ioana Ciornei <ioana.ciornei@nxp.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@nxp.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().
Bart
> + 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
>
>
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@nxp.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@nxp.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
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