[PATCH RFC/RFT 12/15] gpio: sysfs: don't look up exported lines as class devices

[Bartosz Golaszewski <brgl@bgdev.pl>]

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

In preparation for adding a parallel, per-chip attribute group for
exported GPIO lines, stop using class device APIs to refer to it in the
code. When unregistering the chip, don't call class_find_device() but
instead store exported lines in a linked list inside the GPIO chip data
object and look it up there.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib-sysfs.c | 60 ++++++++++++++++++++++++++++++++------------
 1 file changed, 44 insertions(+), 16 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 398cefb4be9e389a820dd53f79c82fa70783b5e0..aa998d9e96cce5d64784645eea73f987471c7285 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -43,6 +43,7 @@ enum {
 
 struct gpiod_data {
 	struct gpio_desc *desc;
+	struct device *dev;
 
 	struct mutex mutex;
 	struct kernfs_node *value_class_node;
@@ -58,12 +59,15 @@ struct gpiod_data {
 	struct attribute *attrs[GPIO_SYSFS_LINE_ATTR_SIZE];
 	struct attribute_group attr_group;
 	const struct attribute_group *attr_groups[2];
+
+	struct list_head list;
 };
 
 struct gpiodev_data {
 	struct gpio_device *gdev;
 	struct device *cdev_base; /* Class device by GPIO base */
 	struct device *cdev_id; /* Class device by GPIO device ID */
+	struct list_head exported_lines;
 };
 
 /*
@@ -686,10 +690,10 @@ static void gpiod_attr_init(struct device_attribute *dev_attr, const char *name,
  */
 int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 {
+	struct gpiodev_data *gdev_data;
 	struct gpiod_data *desc_data;
 	struct gpio_device *gdev;
 	struct attribute **attrs;
-	struct device *dev;
 	int status;
 
 	/* can't export until sysfs is available ... */
@@ -751,25 +755,40 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 	desc_data->attr_group.attrs = desc_data->attrs;
 	desc_data->attr_groups[0] = &desc_data->attr_group;
 
-	dev = device_create_with_groups(&gpio_class, &gdev->dev,
-					MKDEV(0, 0), desc_data,
-					desc_data->attr_groups,
-					"gpio%u", desc_to_gpio(desc));
-	if (IS_ERR(dev)) {
-		status = PTR_ERR(dev);
+	/*
+	 * Note: we need to continue passing desc_data here as there's still
+	 * at least one known user of gpiod_export_link() in the tree. This
+	 * function still uses class_find_device() internally.
+	 */
+	desc_data->dev = device_create_with_groups(&gpio_class, &gdev->dev,
+						   MKDEV(0, 0), desc_data,
+						   desc_data->attr_groups,
+						   "gpio%u",
+						   desc_to_gpio(desc));
+	if (IS_ERR(desc_data->dev)) {
+		status = PTR_ERR(desc_data->dev);
 		goto err_free_data;
 	}
 
-	desc_data->value_class_node = sysfs_get_dirent(dev->kobj.sd, "value");
+	desc_data->value_class_node = sysfs_get_dirent(desc_data->dev->kobj.sd,
+						       "value");
 	if (!desc_data->value_class_node) {
 		status = -ENODEV;
 		goto err_unregister_device;
 	}
 
+	gdev_data = gdev_get_data(gdev);
+	if (!gdev_data) {
+		status = -ENODEV;
+		goto err_unregister_device;
+	}
+
+	list_add(&desc_data->list, &gdev_data->exported_lines);
+
 	return 0;
 
 err_unregister_device:
-	device_unregister(dev);
+	device_unregister(desc_data->dev);
 err_free_data:
 	kfree(desc_data);
 err_clear_bit:
@@ -828,8 +847,9 @@ EXPORT_SYMBOL_GPL(gpiod_export_link);
  */
 void gpiod_unexport(struct gpio_desc *desc)
 {
-	struct gpiod_data *desc_data;
-	struct device *dev;
+	struct gpiod_data *desc_data = NULL;
+	struct gpiodev_data *gdev_data;
+	struct gpio_device *gdev;
 
 	if (!desc) {
 		pr_warn("%s: invalid GPIO\n", __func__);
@@ -840,14 +860,22 @@ void gpiod_unexport(struct gpio_desc *desc)
 		if (!test_bit(FLAG_EXPORT, &desc->flags))
 			return;
 
-		dev = class_find_device(&gpio_class, NULL, desc, match_export);
-		if (!dev)
+		gdev = gpiod_to_gpio_device(desc);
+		gdev_data = gdev_get_data(gdev);
+		if (!gdev_data)
 			return;
 
-		desc_data = dev_get_drvdata(dev);
+		list_for_each_entry(desc_data, &gdev_data->exported_lines, list)
+			if (desc == desc_data->desc)
+				break;
+
+		if (!desc_data)
+			return;
+
+		list_del(&desc_data->list);
 		clear_bit(FLAG_EXPORT, &desc->flags);
 		sysfs_put(desc_data->value_class_node);
-		device_unregister(dev);
+		device_unregister(desc_data->dev);
 
 		/*
 		 * Release irq after deregistration to prevent race with
@@ -857,7 +885,6 @@ void gpiod_unexport(struct gpio_desc *desc)
 			gpio_sysfs_free_irq(desc_data);
 	}
 
-	put_device(dev);
 	mutex_destroy(&desc_data->mutex);
 	kfree(desc_data);
 }
@@ -898,6 +925,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 		return -ENOMEM;
 
 	data->gdev = gdev;
+	INIT_LIST_HEAD(&data->exported_lines);
 
 	guard(mutex)(&sysfs_lock);
 

-- 
2.48.1