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SubjectRe: [PATCH 1/5] gpiolib: introduce set_debounce method
On Mon, 17 May 2010 13:02:30 +0300
felipe.balbi@nokia.com wrote:

> From: Felipe Balbi <felipe.balbi@nokia.com>
>
> Few architectures, like OMAP, allow you to set
> a debouncing time for the gpio before generating
> the IRQ. Teach gpiolib about that.
>
> ...
>
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1447,6 +1447,49 @@ fail:
> }
> EXPORT_SYMBOL_GPL(gpio_direction_output);
>
> +/**
> + * gpio_set_debounce - sets @debounce time for a @gpio
> + * @gpio: the gpio to set debounce time
> + * @debounce: debounce time is microseconds
> + */
> +int gpio_set_debounce(unsigned gpio, unsigned debounce)
> +{
> + unsigned long flags;
> + struct gpio_chip *chip;
> + struct gpio_desc *desc = &gpio_desc[gpio];
> + int status = -EINVAL;
> +
> + spin_lock_irqsave(&gpio_lock, flags);
> +
> + if (!gpio_is_valid(gpio))
> + goto fail;
> + chip = desc->chip;
> + if (!chip || !chip->set || !chip->set_debounce)
> + goto fail;
> + gpio -= chip->base;
> + if (gpio >= chip->ngpio)
> + goto fail;
> + status = gpio_ensure_requested(desc, gpio);
> + if (status < 0)
> + goto fail;
> +
> + /* now we know the gpio is valid and chip won't vanish */
> +
> + spin_unlock_irqrestore(&gpio_lock, flags);
> +
> + might_sleep_if(extra_checks && chip->can_sleep);
> +
> + return chip->set_debounce(chip, gpio, debounce);
> +
> +fail:
> + spin_unlock_irqrestore(&gpio_lock, flags);
> + if (status)
> + pr_debug("%s: gpio-%d status %d\n",
> + __func__, gpio, status);
> +
> + return status;
> +}
> +EXPORT_SYMBOL_GPL(gpio_set_debounce);

nitlet: I suspect this function is taking gpio_lock sooner than it
strictly needs to. Find-tuning that would decrease contention by an
insignificant amount ;)



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