[PATCH v3 3/6] gpiolib: add a per-gpio_device line state notification workqueue

Bartosz Golaszewski
2024-10-15T10:56:36Z

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

In order to prepare the line state notification mechanism for working in
atomic context as well, add a dedicated, high-priority, ordered
workqueue to GPIO device which will be used to queue the events fron any
context for them to be emitted always in process context.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
drivers/gpio/gpiolib-cdev.c | 6 ++++++
drivers/gpio/gpiolib.h | 4 ++++
2 files changed, 10 insertions(+)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index b28751242835..5b28a558c9d0 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -2868,6 +2868,11 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
gdev->chrdev.owner = THIS_MODULE;
gdev->dev.devt = MKDEV(MAJOR(devt), gdev->id);

+ gdev->line_state_wq = alloc_ordered_workqueue(dev_name(&gdev->dev),
+ WQ_HIGHPRI);
+ if (!gdev->line_state_wq)
+ return -ENOMEM;
+
ret = cdev_device_add(&gdev->chrdev, &gdev->dev);
if (ret)
return ret;
@@ -2884,6 +2889,7 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)

void gpiolib_cdev_unregister(struct gpio_device *gdev)
{
+ destroy_workqueue(gdev->line_state_wq);
cdev_device_del(&gdev->chrdev, &gdev->dev);
blocking_notifier_call_chain(&gdev->device_notifier, 0, NULL);
}
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 067197d61d57..d24cd9e8b17c 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -17,6 +17,7 @@
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/srcu.h>
+#include <linux/workqueue.h>

#define GPIOCHIP_NAME "gpiochip"

@@ -44,6 +45,8 @@
* @list: links gpio_device:s together for traversal
* @line_state_notifier: used to notify subscribers about lines being
* requested, released or reconfigured
+ * @line_state_wq: used to emit line state events from a separate thread in
+ * process context
* @device_notifier: used to notify character device wait queues about the GPIO
* device being unregistered
* @srcu: protects the pointer to the underlying GPIO chip
@@ -70,6 +73,7 @@ struct gpio_device {
void *data;
struct list_head list;
struct blocking_notifier_head line_state_notifier;
+ struct workqueue_struct *line_state_wq;
struct blocking_notifier_head device_notifier;
struct srcu_struct srcu;

--
2.43.0