linux-kernel - Re: GPIO: Add generic gpio_to

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Date:	Thu, 24 Jul 2008 12:51:39 +0100
From:	Ben Dooks <ben-linux@...ff.org>
To:	Ben Dooks <ben-linux@...ff.org>
Cc:	linux-kernel@...r.kernel.org, david-b@...bell.net
Subject: Re: GPIO: Add generic gpio_to_irq call.

On Thu, Jul 24, 2008 at 12:46:27PM +0100, Ben Dooks wrote:
> Add gpio_to_irq() implementation allowing the
> gpio_chip registration to also specify an function
> to map GPIO offsets into IRQs.
> 
> Signed-off-by: Ben Dooks <ben-linux@...ff.org>
> 
> Index: linux-2.6.26-quilt3/drivers/gpio/gpiolib.c
> ===================================================================
> --- linux-2.6.26-quilt3.orig/drivers/gpio/gpiolib.c	2008-07-18 13:50:32.000000000 +0100
> +++ linux-2.6.26-quilt3/drivers/gpio/gpiolib.c	2008-07-22 15:20:26.000000000 +0100
> @@ -339,6 +339,36 @@ const char *gpiochip_is_requested(struct
>  }
>  EXPORT_SYMBOL_GPL(gpiochip_is_requested);
>  
> +int __gpio_to_irq(unsigned gpio)
> +{
> +	struct gpio_chip	*chip;
> +	struct gpio_desc	*desc = &gpio_desc[gpio];
> +	unsigned long		flags;
> +	int			status = -EINVAL;
> +
> +	spin_lock_irqsave(&gpio_lock, flags);
> +
> +	if (!gpio_is_valid(gpio))
> +		goto fail;
> +
> +	chip = desc->chip;
> +	if (!chip || !chip->to_irq)
> +		goto fail;
> +
> +	gpio -= chip->base;
> +	if (gpio >= chip->ngpio)
> +		goto fail;
> +
> +	status = chip->to_irq(chip, gpio);

hmm, this should have a check for chip->to_irq
being non-null before it.

> +
> + 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_to_irq);
>  
>  /* Drivers MUST set GPIO direction before making get/set calls.  In
>   * some cases this is done in early boot, before IRQs are enabled.
> Index: linux-2.6.26-quilt3/include/asm-generic/gpio.h
> ===================================================================
> --- linux-2.6.26-quilt3.orig/include/asm-generic/gpio.h	2008-07-18 13:50:32.000000000 +0100
> +++ linux-2.6.26-quilt3/include/asm-generic/gpio.h	2008-07-22 15:21:05.000000000 +0100
> @@ -40,6 +40,7 @@ struct module;
>   * @dbg_show: optional routine to show contents in debugfs; default code
>   *	will be used when this is omitted, but custom code can show extra
>   *	state (such as pullup/pulldown configuration).
> + * @to_irq: convert gpio offset to IRQ number.
>   * @base: identifies the first GPIO number handled by this chip; or, if
>   *	negative during registration, requests dynamic ID allocation.
>   * @ngpio: the number of GPIOs handled by this controller; the last GPIO
> @@ -71,6 +72,9 @@ struct gpio_chip {
>  						unsigned offset, int value);
>  	void			(*dbg_show)(struct seq_file *s,
>  						struct gpio_chip *chip);
> +	int			(*to_irq)(struct gpio_chip *chip,
> +					  unsigned offset);
> +
>  	int			base;
>  	u16			ngpio;
>  	unsigned		can_sleep:1;
> @@ -97,6 +101,7 @@ extern int gpio_direction_output(unsigne
>  extern int gpio_get_value_cansleep(unsigned gpio);
>  extern void gpio_set_value_cansleep(unsigned gpio, int value);
>  
> +extern int __gpio_to_irq(unsigned gpio);
>  
>  /* A platform's <asm/gpio.h> code may want to inline the I/O calls when
>   * the GPIO is constant and refers to some always-present controller,
> Index: linux-2.6.26-quilt3/Documentation/gpio.txt
> ===================================================================
> --- linux-2.6.26-quilt3.orig/Documentation/gpio.txt	2008-07-22 15:22:08.000000000 +0100
> +++ linux-2.6.26-quilt3/Documentation/gpio.txt	2008-07-22 15:27:14.000000000 +0100
> @@ -273,8 +273,9 @@ some GPIOs can't be used as IRQs.)  It i
>  number that wasn't set up as an input using gpio_direction_input(), or
>  to use an IRQ number that didn't originally come from gpio_to_irq().
>  
> -These two mapping calls are expected to cost on the order of a single
> -addition or subtraction.  They're not allowed to sleep.
> +These two mapping calls are expected to cost on between the order of a
> +single addition or subtraction to obtaining an spinlock and using the
> +to_irq method of the relevant gpio chip. They're not allowed to sleep.
>  
>  Non-error values returned from gpio_to_irq() can be passed to request_irq()
>  or free_irq().  They will often be stored into IRQ resources for platform
> @@ -400,6 +401,7 @@ They may also want to provide a custom v
>  Trivial implementations of those functions can directly use framework
>  code, which always dispatches through the gpio_chip:
>  
> +  #define gpio_to_irq	        __gpio_to_irq
>    #define gpio_get_value	__gpio_get_value
>    #define gpio_set_value	__gpio_set_value
>    #define gpio_cansleep		__gpio_cansleep
> 
> -- 
> Ben (ben@...ff.org, http://www.fluff.org/)
> 
>   'a smiley only costs 4 bytes'
> --
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-- 
Ben (ben@...ff.org, http://www.fluff.org/)

  'a smiley only costs 4 bytes'
--
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