linux-kernel - [PATCH] gpiolib: Document that GPIO line names are not globally unique

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Date:   Mon, 11 May 2020 12:18:28 +0200
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH] gpiolib: Document that GPIO line names are not globally unique

gpiochip_set_desc_names() no longer rejects GPIO line name collisions.
Hence GPIO line names are not guaranteed to be globally unique.
In case of multiple GPIO lines with the same name, gpio_name_to_desc()
will return the first match found.

Update the comments for gpio_name_to_desc() and
gpiochip_set_desc_names() to match reality.

Fixes: f881bab038c9667d ("gpio: keep the GPIO line names internal")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
 drivers/gpio/gpiolib.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 99533f4cb5d332a9..98822412f565073a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -296,6 +296,9 @@ static int gpiodev_add_to_list(struct gpio_device *gdev)
 
 /*
  * Convert a GPIO name to its descriptor
+ * Note that there is no guarantee that GPIO names are globally unique!
+ * Hence this function will return, if it exists, a reference to the first GPIO
+ * line found that matches the given name.
  */
 static struct gpio_desc *gpio_name_to_desc(const char * const name)
 {
@@ -329,10 +332,12 @@ static struct gpio_desc *gpio_name_to_desc(const char * const name)
 }
 
 /*
- * Takes the names from gc->names and checks if they are all unique. If they
- * are, they are assigned to their gpio descriptors.
+ * Take the names from gc->names and assign them to their GPIO descriptors.
+ * Warn if a name is already used for a GPIO line on a different GPIO chip.
  *
- * Warning if one of the names is already used for a different GPIO.
+ * Note that:
+ *   1. Non-unique names are still accepted,
+ *   2. Name collisions within the same GPIO chip are not reported.
  */
 static int gpiochip_set_desc_names(struct gpio_chip *gc)
 {
-- 
2.17.1