On Wed, Aug 12, 2009 at 11:49 PM, Heiko Schocher<h...@denx.de> wrote:
> 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 think returning '1' is perhaps slightly 'better' (however you define
that), but I don't think the caller should make any assumptions beyond
zero/non-zero.
>
> 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);
For clarity, the brackets should be just around the & operands, and
"!= 0" instead of "? 1 : 0" might result in slightly smaller code.
return (in_8(mm_gc->regs) & u8_pin2mask(gpio)) != 0;
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
