simple gpio driver

Heiko Schocher hs at
Thu Aug 13 15:49:42 EST 2009

Hello Anton,

i am trying to use the arch/powerpc/sysdev/simple_gpio.c driver,
for accessing some gpios, and found, that u8_gpio_get()
returns not only a 1 or a 0, instead it returns the real bit
position from the gpio:

gpio    return
base	value
0	0/0x01
1	0/0x02
2	0/0x04
3	0/0x08
4	0/0x10
5	0/0x20
6	0/0x40
7	0/0x80

I also use the arch/powerpc/platforms/52xx/mpc52xx_gpio.c and
mpc52xx_gpt.c drivers, they all return for a gpio just a 1 or 0,
which seems correct to me, because a gpio can have only 1 or 0
as state ... what do you think?

I solved this issue (if it is) with the following patch:

diff --git a/arch/powerpc/sysdev/simple_gpio.c b/arch/powerpc/sysdev/simple_gpio.c
index 43c4569..bb0d79c 100644
--- a/arch/powerpc/sysdev/simple_gpio.c
+++ b/arch/powerpc/sysdev/simple_gpio.c
@@ -46,7 +46,7 @@ static int u8_gpio_get(struct gpio_chip *gc, unsigned int gpio)
 	struct of_mm_gpio_chip *mm_gc = to_of_mm_gpio_chip(gc);

-	return in_8(mm_gc->regs) & u8_pin2mask(gpio);
+	return (in_8(mm_gc->regs) & u8_pin2mask(gpio) ? 1 : 0);

 static void u8_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)

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