linux-kernel - [PATCH 1/2] gpiolib: safer implementation of desc_to

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Date:	Fri, 4 Oct 2013 10:59:57 -0700
From:	Alexandre Courbot <acourbot@...dia.com>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	"Dr. H. Nikolaus Schaller" <hns@...delico.com>,
	<linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<gnurou@...il.com>, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH 1/2] gpiolib: safer implementation of desc_to_gpio()

The current implementation of desc_to_gpio() relies on the chip pointer
to be set to a valid value in order to compute the GPIO number. This
was done in the hope that we can get rid of the gpio_desc global array,
but this is not happening anytime soon.

This patch reimplements desc_to_gpio() in a fashion similar to that of
gpio_to_desc(). As a result, desc_to_gpio(gpio_to_desc(gpio)) == gpio is
now always true. This allows to call desc_to_gpio() on non-initialized
descriptors as some error-handling code currently does.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
Reported-by: Dr. H. Nikolaus Schaller <hns@...delico.com>
---
 drivers/gpio/gpiolib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 86ef346..f330631 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -136,7 +136,7 @@ static struct gpio_desc *gpio_to_desc(unsigned gpio)
  */
 static int desc_to_gpio(const struct gpio_desc *desc)
 {
-	return desc->chip->base + gpio_chip_hwgpio(desc);
+	return desc - &gpio_desc[0];
 }

-- 
1.8.4

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