[PATCH v2] gpio: sim: access sysfs attributes as const

[Bartosz Golaszewski]

Use the const variant of constainer_of() to access struct
gpio_sim_attribute which wraps the dynamically allocated sysfs
attributes for value and pull of simulated GPIO lines in line with the
currently preferred approach.

Co-developed-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@xxxxxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
---
Thomas: thanks for the hints! The code you posted compiled fine so I
included it in v2 and gave you credit in the footer.
---
Changes in v2:
- Complete the conversion to const sysfs attributes as suggested by
  Thomas
- Link to v1: https://patch.msgid.link/20261016-gpio-sim-const-sysfs-attr-v1-1-5d2f832890d6@xxxxxxxxxxxxxxxx
---
 drivers/gpio/gpio-sim.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
index 0c73bec042670fc5706b4a93700e652cbaf3605e..34b45d0d357505d7d7ef248560112d3106c50000 100644
--- a/drivers/gpio/gpio-sim.c
+++ b/drivers/gpio/gpio-sim.c
@@ -59,10 +59,10 @@ struct gpio_sim_attribute {
 	unsigned int offset;
 };
 
-static struct gpio_sim_attribute *
-to_gpio_sim_attr(struct device_attribute *dev_attr)
+static const struct gpio_sim_attribute *
+to_gpio_sim_attr(const struct device_attribute *dev_attr)
 {
-	return container_of(dev_attr, struct gpio_sim_attribute, dev_attr);
+	return container_of_const(dev_attr, struct gpio_sim_attribute, dev_attr);
 }
 
 static int gpio_sim_apply_pull(struct gpio_sim_chip *chip,
@@ -270,9 +270,9 @@ static void gpio_sim_dbg_show(struct seq_file *seq, struct gpio_chip *gc)
 }
 
 static ssize_t gpio_sim_sysfs_val_show(struct device *dev,
-				       struct device_attribute *attr, char *buf)
+				       const struct device_attribute *attr, char *buf)
 {
-	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
+	const struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
 	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
 	int val;
 
@@ -283,7 +283,7 @@ static ssize_t gpio_sim_sysfs_val_show(struct device *dev,
 }
 
 static ssize_t gpio_sim_sysfs_val_store(struct device *dev,
-					struct device_attribute *attr,
+					const struct device_attribute *attr,
 					const char *buf, size_t count)
 {
 	/*
@@ -299,10 +299,10 @@ static const char *const gpio_sim_sysfs_pull_strings[] = {
 };
 
 static ssize_t gpio_sim_sysfs_pull_show(struct device *dev,
-					struct device_attribute *attr,
+					const struct device_attribute *attr,
 					char *buf)
 {
-	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
+	const struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
 	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
 	int pull;
 
@@ -313,10 +313,10 @@ static ssize_t gpio_sim_sysfs_pull_show(struct device *dev,
 }
 
 static ssize_t gpio_sim_sysfs_pull_store(struct device *dev,
-					 struct device_attribute *attr,
+					 const struct device_attribute *attr,
 					 const char *buf, size_t len)
 {
-	struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
+	const struct gpio_sim_attribute *line_attr = to_gpio_sim_attr(attr);
 	struct gpio_sim_chip *chip = dev_get_drvdata(dev);
 	int ret, pull;
 
@@ -361,7 +361,7 @@ static int gpio_sim_setup_sysfs(struct gpio_sim_chip *chip)
 	unsigned int num_lines = chip->gc.ngpio;
 	struct device *dev = chip->gc.parent;
 	struct attribute_group *attr_group;
-	struct attribute **attrs;
+	const struct attribute **attrs;
 	int i, ret;
 
 	chip->attr_groups = devm_kcalloc(dev, sizeof(*chip->attr_groups),
@@ -396,15 +396,15 @@ static int gpio_sim_setup_sysfs(struct gpio_sim_chip *chip)
 
 		val_dev_attr->attr.mode = pull_dev_attr->attr.mode = 0644;
 
-		val_dev_attr->show = gpio_sim_sysfs_val_show;
-		val_dev_attr->store = gpio_sim_sysfs_val_store;
-		pull_dev_attr->show = gpio_sim_sysfs_pull_show;
-		pull_dev_attr->store = gpio_sim_sysfs_pull_store;
+		val_dev_attr->show_const = gpio_sim_sysfs_val_show;
+		val_dev_attr->store_const = gpio_sim_sysfs_val_store;
+		pull_dev_attr->show_const = gpio_sim_sysfs_pull_show;
+		pull_dev_attr->store_const = gpio_sim_sysfs_pull_store;
 
 		attrs[0] = &val_dev_attr->attr;
 		attrs[1] = &pull_dev_attr->attr;
 
-		attr_group->attrs = attrs;
+		attr_group->attrs_const = attrs;
 		chip->attr_groups[i] = attr_group;
 	}
 

---
base-commit: 2efb7a11f1aa4d2dc285fe2680cca22cb9f72f64
change-id: 20261016-gpio-sim-const-sysfs-attr-350706cc7500

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>