| Message ID | 20230905185309.131295-5-brgl@bgdev.pl (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | gpio: convert users to gpio_device_find() and remove gpiochip_find() | expand |
On Tue, Sep 05, 2023 at 08:52:52PM +0200, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > Getting the GPIO descriptor directly from the gpio_chip struct is > dangerous as we don't take the reference to the underlying GPIO device. > In order to start working towards removing gpiochip_get_desc(), let's > provide a safer variant that works with an existing reference to struct > gpio_device. ... > +/** > + * gpio_device_get_desc() - get the GPIO descriptor corresponding to the given > + * hardware number for this GPIO device > + * @gdev: GPIO device to get the descriptor from > + * @hwnum: hardware number of the GPIO for this chip > + * > + * Returns: > + * A pointer to the GPIO descriptor or ``ERR_PTR(-EINVAL)`` if no GPIO exists The known constants can be referenced as %EINVAL. > + * in the given chip for the specified hardware number or ``ERR_PTR(-ENODEV)`` Ditto. > + * if the underlying chip already vanished. > + * > + * The reference count of struct gpio_device is *NOT* increased like when the > + * GPIO is being requested for exclusive usage. It's up to the caller to make > + * sure the GPIO device will stay alive together with the descriptor returned > + * by this function. > + */
On Tue, Sep 5, 2023 at 8:53 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote: > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > Getting the GPIO descriptor directly from the gpio_chip struct is > dangerous as we don't take the reference to the underlying GPIO device. > In order to start working towards removing gpiochip_get_desc(), let's > provide a safer variant that works with an existing reference to struct > gpio_device. > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> Andy had some good doc comments, with these addressed: Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Yours, Linus Walleij
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 74b837671d30..4a9af6bfc6d4 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -147,27 +147,48 @@ struct gpio_desc *gpio_to_desc(unsigned gpio) } EXPORT_SYMBOL_GPL(gpio_to_desc); -/** - * gpiochip_get_desc - get the GPIO descriptor corresponding to the given - * hardware number for this chip - * @gc: GPIO chip - * @hwnum: hardware number of the GPIO for this chip - * - * Returns: - * A pointer to the GPIO descriptor or ``ERR_PTR(-EINVAL)`` if no GPIO exists - * in the given chip for the specified hardware number. - */ +/* This function is deprecated and will be removed soon, don't use. */ struct gpio_desc *gpiochip_get_desc(struct gpio_chip *gc, unsigned int hwnum) { - struct gpio_device *gdev = gc->gpiodev; + return gpio_device_get_desc(gc->gpiodev, hwnum); +} +EXPORT_SYMBOL_GPL(gpiochip_get_desc); + +/** + * gpio_device_get_desc() - get the GPIO descriptor corresponding to the given + * hardware number for this GPIO device + * @gdev: GPIO device to get the descriptor from + * @hwnum: hardware number of the GPIO for this chip + * + * Returns: + * A pointer to the GPIO descriptor or ``ERR_PTR(-EINVAL)`` if no GPIO exists + * in the given chip for the specified hardware number or ``ERR_PTR(-ENODEV)`` + * if the underlying chip already vanished. + * + * The reference count of struct gpio_device is *NOT* increased like when the + * GPIO is being requested for exclusive usage. It's up to the caller to make + * sure the GPIO device will stay alive together with the descriptor returned + * by this function. + */ +struct gpio_desc * +gpio_device_get_desc(struct gpio_device *gdev, unsigned int hwnum) +{ + struct gpio_chip *gc = gdev->chip; + + /* + * FIXME: This will be locked once we protect gdev->chip everywhere + * with SRCU. + */ + if (!gc) + return ERR_PTR(-ENODEV); if (hwnum >= gdev->ngpio) return ERR_PTR(-EINVAL); return &gdev->descs[hwnum]; } -EXPORT_SYMBOL_GPL(gpiochip_get_desc); +EXPORT_SYMBOL_GPL(gpio_device_get_desc); /** * desc_to_gpio - convert a GPIO descriptor to the integer namespace diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h index 92f7143bad3e..a769baf3d731 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -766,6 +766,8 @@ struct gpio_desc *gpiochip_request_own_desc(struct gpio_chip *gc, void gpiochip_free_own_desc(struct gpio_desc *desc); struct gpio_desc *gpiochip_get_desc(struct gpio_chip *gc, unsigned int hwnum); +struct gpio_desc * +gpio_device_get_desc(struct gpio_device *gdev, unsigned int hwnum); #ifdef CONFIG_GPIOLIB