Re: simple gpio driver

On Wed, Aug 12, 2009 at 11:49 PM, Heiko Schocher[off-list ref] 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 =A0 =A0return
base =A0 =A0value
0 =A0 =A0 =A0 0/0x01
1 =A0 =A0 =A0 0/0x02
2 =A0 =A0 =A0 0/0x04
3 =A0 =A0 =A0 0/0x08
4 =A0 =A0 =A0 0/0x10
5 =A0 =A0 =A0 0/0x20
6 =A0 =A0 =A0 0/0x40
7 =A0 =A0 =A0 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.

le_gpio.c

nt gpio)

=A0{
=A0 =A0 =A0 =A0struct of_mm_gpio_chip *mm_gc =3D to_of_mm_gpio_chip(gc);

- =A0 =A0 =A0 return in_8(mm_gc->regs) & u8_pin2mask(gpio);
+ =A0 =A0 =A0 return (in_8(mm_gc->regs) & u8_pin2mask(gpio) ? 1 : 0);

For clarity, the brackets should be just around the & operands, and
"!=3D 0" instead of "? 1 : 0" might result in slightly smaller code.

return (in_8(mm_gc->regs) & u8_pin2mask(gpio)) !=3D 0;