Messages in this thread | | | Date | Wed, 26 Nov 2008 13:08:57 +0100 (CET) | From | Geert Uytterhoeven <> | Subject | Re: [Linux-fbdev-devel] [RFC 2.6.27 1/1] gpiolib: add support for batch set of pins |
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On Wed, 26 Nov 2008, Jaya Kumar wrote: > On Wed, Nov 26, 2008 at 5:08 AM, Geert Uytterhoeven > <geert@linux-m68k.org> wrote: > > On Wed, 26 Nov 2008, Jaya Kumar wrote: > >> On Wed, Nov 26, 2008 at 4:09 AM, Paulius Zaleckas > >> <paulius.zaleckas@teltonika.lt> wrote: > >> > Jaya Kumar wrote: > >> >> * @to_irq: optional hook supporting non-static gpio_to_irq() mappings; > >> >> * implementation may not sleep > >> >> * @dbg_show: optional routine to show contents in debugfs; default code > >> >> @@ -84,6 +86,9 @@ struct gpio_chip { > >> >> unsigned offset, int value); > >> >> void (*set)(struct gpio_chip *chip, > >> >> unsigned offset, int value); > >> >> + void (*set_bus)(struct gpio_chip *chip, > >> >> + unsigned offset, int values, > >> > > >> > I think values should be unsigned > >> > >> Okay, can do but it is unusual no? since set uses int value, i figured > >> set_bus should be similar right? > > > > ->set() sets one pin, right? So it's either 0 or 1. > > > > ->set_bus() sets multiple pins. With `int', it will fail for bit 31, as that's > > the sign bit. > > I'm not sure I understood this. I imagine the usage will be like > > int values = 0x8000_0000; > set_bus(..., start_pin, values); > > write_32(register, values); // will still work to set bit 31
Tehcnically, it will work. But it's more confusing if it's int.
> (values >> 31) == 1;
However, be careful with shifts, as right shifts on signed values will duplicate te sign bit.
> > Perhaps you even want u32, to make it clear what's the maximum number of pins > > you can set in one shot? > > Yes, I agree, I will change to use u32 as it is then explicit.
OK. Thx!
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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