Although gpiod_get_direction() can be considered side-effect free for
consumers, its internals involve setting or clearing bits in the
affected GPIO descriptor, for which we need to force-cast the const
descriptor parameter. This could lead to incorrect behavior is the
compiler decide to optimize here, so remove this const parameter. The
intent is to make gpiod_get_direction() private anyway, so it does not
really matter.
Reported-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Alexandre Courbot <[email protected]>
---
drivers/gpio/gpiolib-sysfs.c | 2 +-
drivers/gpio/gpiolib.c | 8 +++-----
include/linux/gpio/consumer.h | 2 +-
3 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 781fbed00fc3..2ac1800b58bb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -41,7 +41,7 @@ static DEFINE_MUTEX(sysfs_lock);
static ssize_t gpio_direction_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- const struct gpio_desc *desc = dev_get_drvdata(dev);
+ struct gpio_desc *desc = dev_get_drvdata(dev);
ssize_t status;
mutex_lock(&sysfs_lock);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5619922ebf44..0b271ef87c09 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -148,7 +148,7 @@ static int gpiochip_find_base(int ngpio)
*
* This function may sleep if gpiod_cansleep() is true.
*/
-int gpiod_get_direction(const struct gpio_desc *desc)
+int gpiod_get_direction(struct gpio_desc *desc)
{
struct gpio_chip *chip;
unsigned offset;
@@ -164,13 +164,11 @@ int gpiod_get_direction(const struct gpio_desc *desc)
if (status > 0) {
/* GPIOF_DIR_IN, or other positive */
status = 1;
- /* FLAG_IS_OUT is just a cache of the result of get_direction(),
- * so it does not affect constness per se */
- clear_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+ clear_bit(FLAG_IS_OUT, &desc->flags);
}
if (status == 0) {
/* GPIOF_DIR_OUT */
- set_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+ set_bit(FLAG_IS_OUT, &desc->flags);
}
return status;
}
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 83c0a61c605d..d54d158ca327 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -66,7 +66,7 @@ __devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
unsigned int index, enum gpiod_flags flags);
void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
-int gpiod_get_direction(const struct gpio_desc *desc);
+int gpiod_get_direction(struct gpio_desc *desc);
int gpiod_direction_input(struct gpio_desc *desc);
int gpiod_direction_output(struct gpio_desc *desc, int value);
int gpiod_direction_output_raw(struct gpio_desc *desc, int value);
--
2.1.3
Hello Alexandre,
just some minor nitpicking on the commit log:
On Tue, Nov 25, 2014 at 04:20:45PM +0900, Alexandre Courbot wrote:
> Although gpiod_get_direction() can be considered side-effect free for
> consumers, its internals involve setting or clearing bits in the
> affected GPIO descriptor, for which we need to force-cast the const
> descriptor parameter. This could lead to incorrect behavior is the
s/ is/ if/, and I think s/parameter/variable to non-const/
> compiler decide to optimize here, so remove this const parameter. The
s/decide/decides/; s/parameter/attribute/
> intent is to make gpiod_get_direction() private anyway, so it does not
> really matter.
>
> Reported-by: Uwe Kleine-K?nig <[email protected]>
Acked-by: Uwe Kleine-K?nig <[email protected]>
Thanks
Uwe
--
Pengutronix e.K. | Uwe Kleine-K?nig |
Industrial Linux Solutions | http://www.pengutronix.de/ |
On 11/25/2014 05:01 PM, Uwe Kleine-K?nig wrote:
> Hello Alexandre,
>
> just some minor nitpicking on the commit log:
>
> On Tue, Nov 25, 2014 at 04:20:45PM +0900, Alexandre Courbot wrote:
>> Although gpiod_get_direction() can be considered side-effect free for
>> consumers, its internals involve setting or clearing bits in the
>> affected GPIO descriptor, for which we need to force-cast the const
>> descriptor parameter. This could lead to incorrect behavior is the
> s/ is/ if/, and I think s/parameter/variable to non-const/
>
>> compiler decide to optimize here, so remove this const parameter. The
> s/decide/decides/; s/parameter/attribute/
>
>> intent is to make gpiod_get_direction() private anyway, so it does not
>> really matter.
>>
>> Reported-by: Uwe Kleine-K?nig <[email protected]>
> Acked-by: Uwe Kleine-K?nig <[email protected]>
Thanks ; I should have proof-read myself...
Sending a v2 with a fixed log and your Ack so Linus can just pick the
patch as-is.
Although gpiod_get_direction() can be considered side-effect free for
consumers, its internals involve setting or clearing bits in the
affected GPIO descriptor, for which we need to force-cast the const
descriptor variable to non-const. This could lead to incorrect behavior
if the compiler decides to optimize here, so remove this const
attribute. The intent is to make gpiod_get_direction() private anyway,
so it does not really matter.
Reported-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Alexandre Courbot <[email protected]>
Acked-by: Uwe Kleine-König <[email protected]>
---
Changes since v1:
- Fixed poor grammar in commit log
- Added Uwe's Ack
drivers/gpio/gpiolib-sysfs.c | 2 +-
drivers/gpio/gpiolib.c | 8 +++-----
include/linux/gpio/consumer.h | 2 +-
3 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 781fbed00fc3..2ac1800b58bb 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -41,7 +41,7 @@ static DEFINE_MUTEX(sysfs_lock);
static ssize_t gpio_direction_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- const struct gpio_desc *desc = dev_get_drvdata(dev);
+ struct gpio_desc *desc = dev_get_drvdata(dev);
ssize_t status;
mutex_lock(&sysfs_lock);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5619922ebf44..0b271ef87c09 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -148,7 +148,7 @@ static int gpiochip_find_base(int ngpio)
*
* This function may sleep if gpiod_cansleep() is true.
*/
-int gpiod_get_direction(const struct gpio_desc *desc)
+int gpiod_get_direction(struct gpio_desc *desc)
{
struct gpio_chip *chip;
unsigned offset;
@@ -164,13 +164,11 @@ int gpiod_get_direction(const struct gpio_desc *desc)
if (status > 0) {
/* GPIOF_DIR_IN, or other positive */
status = 1;
- /* FLAG_IS_OUT is just a cache of the result of get_direction(),
- * so it does not affect constness per se */
- clear_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+ clear_bit(FLAG_IS_OUT, &desc->flags);
}
if (status == 0) {
/* GPIOF_DIR_OUT */
- set_bit(FLAG_IS_OUT, &((struct gpio_desc *)desc)->flags);
+ set_bit(FLAG_IS_OUT, &desc->flags);
}
return status;
}
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 83c0a61c605d..d54d158ca327 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -66,7 +66,7 @@ __devm_gpiod_get_index_optional(struct device *dev, const char *con_id,
unsigned int index, enum gpiod_flags flags);
void devm_gpiod_put(struct device *dev, struct gpio_desc *desc);
-int gpiod_get_direction(const struct gpio_desc *desc);
+int gpiod_get_direction(struct gpio_desc *desc);
int gpiod_direction_input(struct gpio_desc *desc);
int gpiod_direction_output(struct gpio_desc *desc, int value);
int gpiod_direction_output_raw(struct gpio_desc *desc, int value);
--
2.1.3
On Tue, Nov 25, 2014 at 9:16 AM, Alexandre Courbot <[email protected]> wrote:
> Although gpiod_get_direction() can be considered side-effect free for
> consumers, its internals involve setting or clearing bits in the
> affected GPIO descriptor, for which we need to force-cast the const
> descriptor variable to non-const. This could lead to incorrect behavior
> if the compiler decides to optimize here, so remove this const
> attribute. The intent is to make gpiod_get_direction() private anyway,
> so it does not really matter.
>
> Reported-by: Uwe Kleine-König <[email protected]>
> Signed-off-by: Alexandre Courbot <[email protected]>
> Acked-by: Uwe Kleine-König <[email protected]>
> ---
> Changes since v1:
> - Fixed poor grammar in commit log
> - Added Uwe's Ack
Patch applied after crying blood of the quoted-printable encoding
of this mail.
Yours,
Linus Walleij