[PATCH v3 08/10] gpio: aggregator: handle runtime registration of gpio_desc in gpiochip_fwd

Thomas Richard
2025-04-16T14:08:22Z

Add request() callback to check if the GPIO descriptor was well registered
in the gpiochip_fwd before to use it. This is done to handle the case
where GPIO descriptor is added at runtime in the forwarder.

If at least one GPIO descriptor was not added before the forwarder
registration, we assume the forwarder can sleep as if a GPIO is added at
runtime it may sleep.

Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
---
drivers/gpio/gpio-aggregator.c | 27 +++++++++++++++++++++------
include/linux/gpio/forwarder.h | 2 ++
2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
index 5743f84e1310..0fb890f0793d 100644
--- a/drivers/gpio/gpio-aggregator.c
+++ b/drivers/gpio/gpio-aggregator.c
@@ -260,6 +260,14 @@ static void __exit gpio_aggregator_remove_all(void)

#define fwd_tmp_size(ngpios) (BITS_TO_LONGS((ngpios)) + (ngpios))

+int gpio_fwd_request(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
+
+ return fwd->descs[offset] ? 0 : -ENODEV;
+}
+EXPORT_SYMBOL_NS_GPL(gpio_fwd_request, "GPIO_FORWARDER");
+
int gpio_fwd_get_direction(struct gpio_chip *chip, unsigned int offset)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
@@ -513,6 +521,7 @@ devm_gpio_fwd_alloc(struct device *dev, unsigned int ngpios)
chip->label = label;
chip->parent = dev;
chip->owner = THIS_MODULE;
+ chip->request = gpio_fwd_request;
chip->get_direction = gpio_fwd_get_direction;
chip->direction_input = gpio_fwd_direction_input;
chip->direction_output = gpio_fwd_direction_output;
@@ -531,7 +540,6 @@ EXPORT_SYMBOL_NS_GPL(devm_gpio_fwd_alloc, "GPIO_FORWARDER");
int gpio_fwd_add_gpio_desc(struct gpiochip_fwd *fwd, struct gpio_desc *desc,
unsigned int offset)
{
- struct gpio_chip *parent = gpiod_to_chip(desc);
struct gpio_chip *chip = &fwd->chip;

if (offset > chip->ngpio)
@@ -543,15 +551,10 @@ int gpio_fwd_add_gpio_desc(struct gpiochip_fwd *fwd, struct gpio_desc *desc,
/*
* If any of the GPIO lines are sleeping, then the entire forwarder
* will be sleeping.
- * If any of the chips support .set_config(), then the forwarder will
- * support setting configs.
*/
if (gpiod_cansleep(desc))
chip->can_sleep = true;

- if (parent && parent->set_config)
- chip->set_config = gpio_fwd_set_config;
-
fwd->descs[offset] = desc;

dev_dbg(chip->parent, "%u => gpio %d irq %d\n", offset,
@@ -564,8 +567,20 @@ EXPORT_SYMBOL_NS_GPL(gpio_fwd_add_gpio_desc, "GPIO_FORWARDER");
int gpio_fwd_register(struct gpiochip_fwd *fwd)
{
struct gpio_chip *chip = &fwd->chip;
+ unsigned int ndescs = 0, i;
int error;

+ for (i = 0; i < chip->ngpio; i++)
+ if (fwd->descs[i])
+ ndescs++;
+
+ /*
+ * Some gpio_desc were not registers. They will be registered at runtime
+ * but we have to suppose they can sleep.
+ */
+ if (ndescs != chip->ngpio)
+ chip->can_sleep = true;
+
if (chip->can_sleep)
mutex_init(&fwd->mlock);
else
diff --git a/include/linux/gpio/forwarder.h b/include/linux/gpio/forwarder.h
index 78adfe6f162f..f3fba3c39bda 100644
--- a/include/linux/gpio/forwarder.h
+++ b/include/linux/gpio/forwarder.h
@@ -27,6 +27,8 @@ struct gpiochip_fwd {
unsigned long tmp[]; /* values and descs for multiple ops */
};

+int gpio_fwd_request(struct gpio_chip *chip, unsigned int offset);
+
int gpio_fwd_get_direction(struct gpio_chip *chip, unsigned int offset);

int gpio_fwd_direction_input(struct gpio_chip *chip, unsigned int offset);

--
2.39.5