gpiolib: provide gpiochip_dup_line_label()

gpiochip_is_requested() not only has a misleading name but it returns
a pointer to a string that is freed when the descriptor is released.

Provide a new helper meant to replace it, which returns a copy of the
label string instead.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 30 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 95d2a7b2ea3e..0147c900afea 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2387,6 +2387,35 @@ const char *gpiochip_is_requested(struct gpio_chip *gc, unsigned int offset)
 EXPORT_SYMBOL_GPL(gpiochip_is_requested);
 
 /**
+ * gpiochip_dup_line_label - Get a copy of the consumer label.
+ * @gc: GPIO chip controlling this line.
+ * @offset: Hardware offset of the line.
+ *
+ * Returns:
+ * Pointer to a copy of the consumer label if the line is requested or NULL
+ * if it's not. If a valid pointer was returned, it must be freed using
+ * kfree(). In case of a memory allocation error, the function returns %ENOMEM.
+ *
+ * Must not be called from atomic context.
+ */
+char *gpiochip_dup_line_label(struct gpio_chip *gc, unsigned int offset)
+{
+	const char *label;
+	char *copy;
+
+	label = gpiochip_is_requested(gc, offset);
+	if (!label)
+		return NULL;
+
+	copy = kstrdup(label, GFP_KERNEL);
+	if (!copy)
+		return ERR_PTR(-ENOMEM);
+
+	return copy;
+}
+EXPORT_SYMBOL_GPL(gpiochip_dup_line_label);
+
+/**
  * gpiochip_request_own_desc - Allow GPIO chip to request its own descriptor
  * @gc: GPIO chip
  * @hwnum: hardware number of the GPIO for which to request the descriptor
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 0aed62f0c633..5ac6dc30c547 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -532,6 +532,7 @@ struct gpio_chip {
 };
 
 const char *gpiochip_is_requested(struct gpio_chip *gc, unsigned int offset);
+char *gpiochip_dup_line_label(struct gpio_chip *gc, unsigned int offset);
 
 /**
  * for_each_requested_gpio_in_range - iterates over requested GPIOs in a given range