Messages in this thread | | | Date | Mon, 17 Nov 2014 10:09:15 +0100 | From | Uwe Kleine-König <> | Subject | Re: [PATCH 2/4] gpiolib: use const parameters when possible |
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Hello,
On Wed, Feb 13, 2013 at 04:03:00PM +0900, Alexandre Courbot wrote: > From: Alexandre Courbot <acourbot@nvidia.com> > > Constify descriptor parameter of gpiod_* functions for those that > should obviously not modify it. This includes value or direction get, > cansleep, and IRQ number query. > > Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> This patch is applied as def634338d3ffb32fbe9b0a2d70cc24ef909cd4f since v3.9-rc2.
> drivers/gpio/gpiolib.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index 8a2cf9c..ad6df6b 100644 > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -207,7 +208,7 @@ static int gpiochip_find_base(int ngpio) > } > > /* caller ensures gpio is valid and requested, chip->get_direction may sleep */ > -static int gpiod_get_direction(struct gpio_desc *desc) > +static int gpiod_get_direction(const struct gpio_desc *desc) > { > struct gpio_chip *chip; > unsigned offset; > @@ -223,11 +224,13 @@ static int gpiod_get_direction(struct gpio_desc *desc) > if (status > 0) { > /* GPIOF_DIR_IN, or other positive */ > status = 1; > - clear_bit(FLAG_IS_OUT, &desc->flags); > + /* 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); I think this is worse than not having gpiod_get_direction take a const descriptor. I don't know an example for this particular case where this could break, but usually casting away a const is bad and can break in various ways.
Maybe even drop the public function gpiod_get_direction completely. As of next-20141114 there are only two users of this function (apart from drivers/gpio/gpiolib*) and both are wrong (as discussed in http://thread.gmane.org/gmane.linux.serial/16808/focus=4783).
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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