[PATCH v2 0/2] gpiolib: gpio_device label improvements

[PATCH v2 0/2] gpiolib: gpio_device label improvements

[Bartosz Golaszewski]

Avoid unnecessary memory allocations with kstrdup_const().

v1 -> v2:
- use a ternary operator instead of an if/else in patch 2/2

Bartosz Golaszewski (2):
  gpiolib: constify label in gpio_device
  gpiolib: use kstrdup_const() for gpio_device label

 drivers/gpio/gpiolib.c | 9 +++------
 drivers/gpio/gpiolib.h | 2 +-
 2 files changed, 4 insertions(+), 7 deletions(-)

-- 
2.15.1

[PATCH v2 1/2] gpiolib: constify label in gpio_device

[Bartosz Golaszewski]

This string is never modified. Make it const.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
---
 drivers/gpio/gpiolib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 5e1f7cc6eeb6..6e9228b94437 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -58,7 +58,7 @@ struct gpio_device {
 	struct gpio_desc	*descs;
 	int			base;
 	u16			ngpio;
-	char			*label;
+	const char		*label;
 	void			*data;
 	struct list_head        list;
 
-- 
2.15.1

[PATCH v2 2/2] gpiolib: use kstrdup_const() for gpio_device label

[Bartosz Golaszewski]

Users often pass a pointer to a static string to gpiochip_add_data()
family of functions. Avoid unnecessary memory allocations with the
provided helper routine.

While at it: use a ternary operator instead of an if else for brevity.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
---
 drivers/gpio/gpiolib.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 56eec094184c..e9ec44ffaaaf 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1062,7 +1062,7 @@ static void gpiodevice_release(struct device *dev)
 
 	list_del(&gdev->list);
 	ida_simple_remove(&gpio_ida, gdev->id);
-	kfree(gdev->label);
+	kfree_const(gdev->label);
 	kfree(gdev->descs);
 	kfree(gdev);
 }
@@ -1170,10 +1170,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 		goto err_free_descs;
 	}
 
-	if (chip->label)
-		gdev->label = kstrdup(chip->label, GFP_KERNEL);
-	else
-		gdev->label = kstrdup("unknown", GFP_KERNEL);
+	gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
 	if (!gdev->label) {
 		status = -ENOMEM;
 		goto err_free_descs;
@@ -1294,7 +1291,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
 	list_del(&gdev->list);
 	spin_unlock_irqrestore(&gpio_lock, flags);
 err_free_label:
-	kfree(gdev->label);
+	kfree_const(gdev->label);
 err_free_descs:
 	kfree(gdev->descs);
 err_free_gdev:
-- 
2.15.1

Re: [PATCH v2 2/2] gpiolib: use kstrdup_const() for gpio_device label

[Linus Walleij]

On Thu, Dec 14, 2017 at 3:29 PM, Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> Users often pass a pointer to a static string to gpiochip_add_data()
> family of functions. Avoid unnecessary memory allocations with the
> provided helper routine.
>
> While at it: use a ternary operator instead of an if else for brevity.
>
> Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Patch applied. (Patch 1/2 was already applied from an earlier
version).

Yours,
Linus Walleij