linux-kernel - Re: [PATCH] gpiolib: add gpio_request/free

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Date:	Fri, 5 Jun 2009 22:19:47 -0700
From:	David Brownell <david-b@...bell.net>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: add gpio_request/free_irq

On Friday 05 June 2009, H Hartley Sweeten wrote:
> Add support functions to gpiolib to request/free gpio irqs.

I'm not keen on this.

 - At best it's a convenience layer ... for something that's
   not the least bit awkward to do otherwise.

 - Coupling it to gpiolib sort of defeats the point of saying
   that gpiolib is just an *implementation* of the interface.
   Where's the code to run for non-gpiolib platforms?

 - Since it implicitly couples gpio_request() to a flavor of
   request_irq(), it precludes sharing those IRQs.

Basically, board setup can know that the GPIO is being used
as an IRQ, and do the request()/direction_input() before it
passes gpio_to_irq() to the driver. That's worked in every
case I've happened across so far...

- Dave



> 
> Signed-off-by: H Hartley Sweeten <hsweeten@...ionengravers.com>
> Cc: David Brownell <dbrownell@...rs.sourceforge.net>
> 
> ---
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 51a8d41..5b4b864 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1103,6 +1103,52 @@ int __gpio_to_irq(unsigned gpio)
>  }
>  EXPORT_SYMBOL_GPL(__gpio_to_irq);
>  
> +/**
> + * gpio_request_irq() - allocate a gpio interrupt line
> + * @gpio: gpio whose IRQ will be allocated
> + * @handler: function to be called when the IRQ occurs
> + * @irqflags: interrupt type flags
> + * @label: an ascii name for the claiming device
> + * @data: a cookie passed back to the handling function
> + */
> +int gpio_request_irq(unsigned gpio, irq_handler_t handler,
> +			unsigned long irqflags, const char *label, void *data)
> +{
> +	int err;
> +
> +	err = gpio_request(gpio, label);
> +	if (err)
> +		goto fail;
> +
> +	err = gpio_direction_input(gpio);
> +	if (err)
> +		goto free;
> +
> +	err = request_irq(gpio_to_irq(gpio), handler, irqflags, label, data);
> +	if (err)
> +		goto free;
> +
> +	return 0;
> +
> +free:
> +	gpio_free(gpio);
> +fail:
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(gpio_request_irq);
> +
> +/**
> + * gpio_free_irq() - free an interrupt allocated with gpio_request_irq
> + * @irq: gpio interrupt line to free
> + * @data: device identity to free
> + */
> +void gpio_free_irq(unsigned int irq, void *data)
> +{
> +	free_irq(irq, data);
> +	gpio_free(irq_to_gpio(irq));
> +}
> +EXPORT_SYMBOL_GPL(gpio_free_irq);
> +
>  
>  
>  /* There's no value in making it easy to inline GPIO calls that may sleep.
> diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
> index d6c379d..c0ab7cf 100644
> --- a/include/asm-generic/gpio.h
> +++ b/include/asm-generic/gpio.h
> @@ -3,6 +3,7 @@
>  
>  #include <linux/types.h>
>  #include <linux/errno.h>
> +#include <linux/interrupt.h>
>  
>  #ifdef CONFIG_GPIOLIB
>  
> @@ -134,6 +135,11 @@ extern int __gpio_cansleep(unsigned gpio);
>  
>  extern int __gpio_to_irq(unsigned gpio);
>  
> +/* request/free gpio interrupt */
> +extern int gpio_request_irq(unsigned gpio, irq_handler_t handler,
> +			unsigned long irqflags, const char *label, void *data);
> +extern void gpio_free_irq(unsigned int irq, void *data);
> +
>  #ifdef CONFIG_GPIO_SYSFS
>  
>  /*
> diff --git a/include/linux/gpio.h b/include/linux/gpio.h
> index e10c49a..eaf7b27 100644
> --- a/include/linux/gpio.h
> +++ b/include/linux/gpio.h
> @@ -109,6 +109,18 @@ static inline int irq_to_gpio(unsigned irq)
>  	return -EINVAL;
>  }
>  
> +static inline int gpio_request_irq(unsigned gpio, irq_handler_t handler,
> +			unsigned long irqflags, const char *label, void *data)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline void gpio_free_irq(unsigned int irq, void *data)
> +{
> +	/* GPIO irq can never have been requested */
> +	WARN_ON(1);
> +}
> +
>  #endif
>  
>  #endif /* __LINUX_GPIO_H */
> 
> 


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