Re: [PATCH 1/2] gpiolib: add gpiochip_get_desc() driver function

[Jean-Jacques Hiblot <jjhiblot@traphandler.com>]

Hi Alexandre,

2014-02-09 9:43 GMT+01:00 Alexandre Courbot <acourbot@nvidia.com>:
> Some drivers dealing with a gpio_chip might need to act on its
> descriptors directly; one example is pinctrl drivers that need to lock a
> GPIO for being used as IRQ using gpiod_lock_as_irq().
>
> This patch exports a gpiochip_get_desc() function that returns the
> GPIO descriptor at the requested index. It also sweeps the
> gpio_to_chip() function out of the consumer interface since any holder
> of a gpio_chip reference can manipulate its GPIOs way beyond what a
> consumer should be allowed to do.
>
> As a result, gpio_chip is not visible anymore to simple GPIO consumers.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> Jean-Jacques, I think you will want to use this function for locking GPIOs
> in the AT91 pinctrl driver. Mika, we talked about this a while ago already,
> but here it is finally. Next patch uses it in the GPIO ACPI driver.
Thanks for the feature. At the moment though I'm still using the
wrapper gpio_lock_as_irq().

Reviewed-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>

>
>  drivers/gpio/gpiolib.c        | 17 +++++++++--------
>  include/linux/gpio/consumer.h |  8 --------
>  include/linux/gpio/driver.h   | 18 ++++++++++++++++++
>  3 files changed, 27 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 50c4922..f60d74b 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -164,16 +164,17 @@ struct gpio_desc *gpio_to_desc(unsigned gpio)
>  EXPORT_SYMBOL_GPL(gpio_to_desc);
>
>  /**
> - * Convert an offset on a certain chip to a corresponding descriptor
> + * Get the GPIO descriptor corresponding to the given hw number for this chip.
>   */
> -static struct gpio_desc *gpiochip_offset_to_desc(struct gpio_chip *chip,
> -                                                unsigned int offset)
> +struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip,
> +                                   u16 hwnum)
>  {
> -       if (offset >= chip->ngpio)
> +       if (hwnum >= chip->ngpio)
>                 return ERR_PTR(-EINVAL);
>
> -       return &chip->desc[offset];
> +       return &chip->desc[hwnum];
>  }
> +EXPORT_SYMBOL_GPL(gpiochip_get_desc);
>
>  /**
>   * Convert a GPIO descriptor to the integer namespace.
> @@ -2161,7 +2162,7 @@ EXPORT_SYMBOL_GPL(gpiod_lock_as_irq);
>
>  int gpio_lock_as_irq(struct gpio_chip *chip, unsigned int offset)
>  {
> -       return gpiod_lock_as_irq(gpiochip_offset_to_desc(chip, offset));
> +       return gpiod_lock_as_irq(gpiochip_get_desc(chip, offset));
>  }
>  EXPORT_SYMBOL_GPL(gpio_lock_as_irq);
>
> @@ -2183,7 +2184,7 @@ EXPORT_SYMBOL_GPL(gpiod_unlock_as_irq);
>
>  void gpio_unlock_as_irq(struct gpio_chip *chip, unsigned int offset)
>  {
> -       return gpiod_unlock_as_irq(gpiochip_offset_to_desc(chip, offset));
> +       return gpiod_unlock_as_irq(gpiochip_get_desc(chip, offset));
>  }
>  EXPORT_SYMBOL_GPL(gpio_unlock_as_irq);
>
> @@ -2404,7 +2405,7 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
>                         return ERR_PTR(-EINVAL);
>                 }
>
> -               desc = gpiochip_offset_to_desc(chip, p->chip_hwnum);
> +               desc = gpiochip_get_desc(chip, p->chip_hwnum);
>                 *flags = p->flags;
>
>                 return desc;
> diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
> index 7a8144f..f6a9cc3 100644
> --- a/include/linux/gpio/consumer.h
> +++ b/include/linux/gpio/consumer.h
> @@ -5,7 +5,6 @@
>  #include <linux/kernel.h>
>
>  struct device;
> -struct gpio_chip;
>
>  /**
>   * Opaque descriptor for a GPIO. These are obtained using gpiod_get() and are
> @@ -59,7 +58,6 @@ int gpiod_to_irq(const struct gpio_desc *desc);
>  /* Convert between the old gpio_ and new gpiod_ interfaces */
>  struct gpio_desc *gpio_to_desc(unsigned gpio);
>  int desc_to_gpio(const struct gpio_desc *desc);
> -struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc);
>
>  #else /* CONFIG_GPIOLIB */
>
> @@ -207,12 +205,6 @@ static inline int desc_to_gpio(const struct gpio_desc *desc)
>         WARN_ON(1);
>         return -EINVAL;
>  }
> -static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
> -{
> -       /* GPIO can never have been requested */
> -       WARN_ON(1);
> -       return ERR_PTR(-ENODEV);
> -}
>
>
>  #endif /* CONFIG_GPIOLIB */
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index a3e181e..9fe2836 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -10,6 +10,8 @@ struct of_phandle_args;
>  struct device_node;
>  struct seq_file;
>
> +#ifdef CONFIG_GPIOLIB
> +
>  /**
>   * struct gpio_chip - abstract a GPIO controller
>   * @label: for diagnostics
> @@ -129,6 +131,11 @@ extern struct gpio_chip *gpiochip_find(void *data,
>  int gpiod_lock_as_irq(struct gpio_desc *desc);
>  void gpiod_unlock_as_irq(struct gpio_desc *desc);
>
> +struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc);
> +
> +struct gpio_desc *gpiochip_get_desc(struct gpio_chip *chip,
> +                                   u16 hwnum);
> +
>  enum gpio_lookup_flags {
>         GPIO_ACTIVE_HIGH = (0 << 0),
>         GPIO_ACTIVE_LOW = (1 << 0),
> @@ -183,4 +190,15 @@ struct gpiod_lookup_table {
>
>  void gpiod_add_lookup_table(struct gpiod_lookup_table *table);
>
> +#else /* CONFIG_GPIOLIB */
> +
> +static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)
> +{
> +       /* GPIO can never have been requested */
> +       WARN_ON(1);
> +       return ERR_PTR(-ENODEV);
> +}
> +
> +#endif /* CONFIG_GPIOLIB */
> +
>  #endif
> --
> 1.8.5.4
>