Re: [PATCH v2 1/2] gpio: regmap: Support sparsed fixed direction
From: Alex Elder
Date: Sun May 10 2026 - 09:31:44 EST
On 5/8/26 8:03 AM, Alex Elder wrote:
On 5/8/26 7:51 AM, Linus Walleij wrote:
On some regmapped GPIOs apparently only a sparser selection
of the lines (not all) are actually fixed direction.
Support this situation by adding an optional bitmap indicating
which GPIOs are actually fixed direction and which are not.
Cc: Alex Elder <elder@xxxxxxxxxxxx>
Link: https://lore.kernel.org/linux-gpio/20260501155421.3329862-10- elder@xxxxxxxxxxxx/
Tested-by: Alex Elder <elder@xxxxxxxxxxxx>
Signed-off-by: Linus Walleij <linusw@xxxxxxxxxx>
In addition, it would be fine with me if you merged this together
iwth your new patch:
https://lore.kernel.org/lkml/20260508-regmap-gpio-sparse-fixed-dir-v2-2- deee84df3027@xxxxxxxxxx/
It makes sense and it is logically part of the same change.
I even tested with that change applied, even though I know
just by inspection it will do what's desired.
Anyway, for both (or a combined single patch), these apply:
Tested-by: Alex Elder <elder@xxxxxxxxxxxx>
Reviewed-by: Alex Elder <elder@xxxxxxxxxxxx>
-Alex
I had another look at this and I had two more comments. I
don't care whether you address them or not, but I thought
I'd mention them.
The first is, in gpio_regmap_set_direction(), if a request to
set the direction to something that isn't supported (e.g. set
the direction to input on an output-only GPIO), shouldn't it
return an error to indicate nothing happened? (-EINVAL or
-ENOTSUP maybe?)
Doing that might not be as simple as it seems, and maybe you
just opted to keep it simple. gpio_regmap_direction_output()
calls gpio_regmap_set() before setting the direction, so
checking whether it's valid happens later than desired.
The second is a missing blank line that I didn't expect,
in gpio_regmap_get_direction(). I mention it in context
below.
-Alex
---
drivers/gpio/gpio-regmap.c | 37 +++++++++++++++++++++++++++++++++----
include/linux/gpio/regmap.h | 7 +++++++
2 files changed, 40 insertions(+), 4 deletions(-)
diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 9ae4a41a2427..f45a432e8ebe 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_sparse;
unsigned long *fixed_direction_output;
#ifdef CONFIG_REGMAP_IRQ
@@ -138,6 +139,20 @@ static int gpio_regmap_set_with_clear(struct gpio_chip *chip,
return regmap_write(gpio->regmap, reg, mask);
}
+static bool gpio_regmap_fixed_direction(struct gpio_regmap *gpio,
+ unsigned int offset)
+{
+ if (!gpio->fixed_direction_output)
+ return false;
+
+ /* In this case only some GPIOs are fixed as input/output */
+ if (gpio->fixed_direction_sparse &&
+ !test_bit(offset, gpio->fixed_direction_sparse))
+ return false;
+
+ return true;
+}
+
static int gpio_regmap_get_direction(struct gpio_chip *chip,
unsigned int offset)
{
@@ -145,7 +160,7 @@ static int gpio_regmap_get_direction(struct gpio_chip *chip,
unsigned int base, val, reg, mask;
int invert, ret;
This isn't new, but why is there no blank line here?
- if (gpio->fixed_direction_output) {
+ if (gpio_regmap_fixed_direction(gpio, offset)) {
if (test_bit(offset, gpio->fixed_direction_output))
return GPIO_LINE_DIRECTION_OUT;
else
@@ -302,12 +317,23 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
goto err_free_gpio;
}
+ if (config->fixed_direction_sparse) {
+ gpio->fixed_direction_sparse = bitmap_alloc(chip->ngpio,
+ GFP_KERNEL);
+ if (!gpio->fixed_direction_sparse) {
+ ret = -ENOMEM;
+ goto err_free_gpio;
+ }
+ bitmap_copy(gpio->fixed_direction_sparse,
+ config->fixed_direction_sparse, chip->ngpio);
+ }
+
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;
+ goto err_free_bitmap_sparse;
}
bitmap_copy(gpio->fixed_direction_output,
config->fixed_direction_output, chip->ngpio);
@@ -329,7 +355,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
ret = gpiochip_add_data(chip, gpio);
if (ret < 0)
- goto err_free_bitmap;
+ goto err_free_bitmap_output;
#ifdef CONFIG_REGMAP_IRQ
if (config->regmap_irq_chip) {
@@ -355,8 +381,10 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
err_remove_gpiochip:
gpiochip_remove(chip);
-err_free_bitmap:
+err_free_bitmap_output:
bitmap_free(gpio->fixed_direction_output);
+err_free_bitmap_sparse:
+ bitmap_free(gpio->fixed_direction_sparse);
err_free_gpio:
kfree(gpio);
return ERR_PTR(ret);
@@ -376,6 +404,7 @@ void gpio_regmap_unregister(struct gpio_regmap *gpio)
gpiochip_remove(&gpio->gpio_chip);
bitmap_free(gpio->fixed_direction_output);
+ bitmap_free(gpio->fixed_direction_sparse);
kfree(gpio);
}
EXPORT_SYMBOL_GPL(gpio_regmap_unregister);
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index 12d154732ca9..ff00b4aeaf1c 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -38,6 +38,12 @@ struct regmap;
* offset to a register/bitmask pair. If not
* given the default gpio_regmap_simple_xlate()
* is used.
+ * @fixed_direction_sparse:
+ * (Optional) Bitmap representing the GPIO lines that
+ * make use of the @fixed_direction_output list to
+ * enforce direction of the GPIO. If this is NULL
+ * and @fixed_direction_output is defined, ALL GPIOs
+ * are assumed to be fixed direction (out or in).
* @fixed_direction_output:
* (Optional) Bitmap representing the fixed direction of
* the GPIO lines. Useful when there are GPIO lines with a
@@ -89,6 +95,7 @@ struct gpio_regmap_config {
int reg_stride;
int ngpio_per_reg;
struct irq_domain *irq_domain;
+ unsigned long *fixed_direction_sparse;
unsigned long *fixed_direction_output;
#ifdef CONFIG_REGMAP_IRQ