[PATCH v3 08/24] gpio: sysfs: use gpio_device_find() to iterate over existing devices

Bartosz Golaszewski
2024-02-08T09:59:35Z

With the list of GPIO devices now protected with SRCU we can use
gpio_device_find() to traverse it from sysfs.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
drivers/gpio/gpiolib-sysfs.c | 46 ++++++++++++++++++------------------
drivers/gpio/gpiolib.c | 2 +-
drivers/gpio/gpiolib.h | 1 -
3 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6bf5332136e5..d6ff044ce887 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -790,11 +790,29 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
}
}

+/*
+ * We're not really looking for a device - we just want to iterate over the
+ * list and call this callback for each GPIO device. This is why this function
+ * always returns 0.
+ */
+static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
+{
+ struct gpio_device *gdev = gc->gpiodev;
+ int ret;
+
+ if (gdev->mockdev)
+ return 0;
+
+ ret = gpiochip_sysfs_register(gdev);
+ if (ret)
+ chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
+
+ return 0;
+}
+
static int __init gpiolib_sysfs_init(void)
{
- int status;
- unsigned long flags;
- struct gpio_device *gdev;
+ int status;

status = class_register(&gpio_class);
if (status < 0)
@@ -806,26 +824,8 @@ static int __init gpiolib_sysfs_init(void)
* We run before arch_initcall() so chip->dev nodes can have
* registered, and so arch_initcall() can always gpiod_export().
*/
- spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(gdev, &gpio_devices, list) {
- if (gdev->mockdev)
- continue;
+ (void)gpio_device_find(NULL, gpiofind_sysfs_register);

- /*
- * TODO we yield gpio_lock here because
- * gpiochip_sysfs_register() acquires a mutex. This is unsafe
- * and needs to be fixed.
- *
- * Also it would be nice to use gpio_device_find() here so we
- * can keep gpio_chips local to gpiolib.c, but the yield of
- * gpio_lock prevents us from doing this.
- */
- spin_unlock_irqrestore(&gpio_lock, flags);
- status = gpiochip_sysfs_register(gdev);
- spin_lock_irqsave(&gpio_lock, flags);
- }
- spin_unlock_irqrestore(&gpio_lock, flags);
-
- return status;
+ return 0;
}
postcore_initcall(gpiolib_sysfs_init);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a87ab8f013c4..68543ab34fb6 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -85,7 +85,7 @@ DEFINE_SPINLOCK(gpio_lock);
static DEFINE_MUTEX(gpio_lookup_lock);
static LIST_HEAD(gpio_lookup_list);

-LIST_HEAD(gpio_devices);
+static LIST_HEAD(gpio_devices);
/* Protects the GPIO device list against concurrent modifications. */
static DEFINE_MUTEX(gpio_devices_lock);
/* Ensures coherence during read-only accesses to the list of GPIO devices. */
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index d2e73eea9e92..2bf3f9e13ae4 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -136,7 +136,6 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);

extern spinlock_t gpio_lock;
-extern struct list_head gpio_devices;

void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);

--
2.40.1