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 <[email protected]>
---
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
pon., 11 maj 2020 o 12:18 Geert Uytterhoeven <[email protected]>
napisał(a):
>
> 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 <[email protected]>
> ---
> 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
>
This makes me wonder whether I should do something about this in
libgpiod? Looks to me like gpiod_chip_find_line() and the global
gpiod_line_find() are no longer reliable and should probably return
all lines whose names match.
Bart
On Mon, May 11, 2020 at 12:18 PM Geert Uytterhoeven
<[email protected]> wrote:
> 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 <[email protected]>
Patch applied.
Yours,
Linus Walleij
On Tue, May 12, 2020 at 12:43 PM Bartosz Golaszewski
<[email protected]> wrote:
> pon., 11 maj 2020 o 12:18 Geert Uytterhoeven <[email protected]>
> napisał(a):
> >
> > 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.
(...)
> This makes me wonder whether I should do something about this in
> libgpiod? Looks to me like gpiod_chip_find_line() and the global
> gpiod_line_find() are no longer reliable and should probably return
> all lines whose names match.
Hm. You probably know how consumers of libgpiod work better than me.
The background is historical and this happens because gpiolib had a
mechanism to name lines before I even took over maintenance, and
that did not require line names to be unique. So
when I created the character device I had to face the fact.
We also had to deal with the fact that when naming lines, the
"NULL alternative" (no name on the line at all) is always a valid
fallback.
And all lines named NULL are still valid and all have the same name
so...
Yours,
Linus Walleij