Re: [patch] input: Fix CLOCK_TICK_RATE usage ... [8/13]

Vojtech Pavlik (vojtech@suse.cz)
Wed, 18 Jun 2003 01:31:14 +0200


On Tue, Jun 17, 2003 at 04:24:04PM -0700, David Mosberger wrote:
> >>>>> On Wed, 18 Jun 2003 01:14:11 +0200, Vojtech Pavlik <vojtech@suse.cz> said:
>
> >> Sounds much better to me. Wouldn't something along the lines of
> >> this make the most sense:
>
> >> #ifdef __ARCH_PIT_FREQ # define PIT_FREQ __ARCH_PIT_FREQ #else #
> >> define PIT_FREQ 1193182 #endif
>
> >> After all, it seems like the vast majority of legacy-compatible
> >> hardware _do_ use the standard frequency.
>
> Vojtech> Now, if this was in some nice include file, along with the
> Vojtech> definition of the i8253 PIT spinlock, that'd be
> Vojtech> great. Because not just the beeper driver uses the PIT,
> Vojtech> also some joystick code uses it if it is available.
>
> ftape, too. The LATCH() macro should also be moved to such a header
> file, I think. How about just creating asm/pit.h? Only platforms
> that need to (potentially) support legacy hardware would need to
> define it. E.g., on ia64, we could do:
>
> #ifndef _ASM_IA64_PIT_H
> #define _ASM_IA64_PIT_H
>
> #include <linux/config.h>
>
> #ifdef CONFIG_LEGACY_HW
> # define PIT_FREQ 1193182
> # define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ)
> #endif
>
> #endif /* _ASM_IA64_PIT_H */
>
> This way, machines that support legacy hardware can define
> CONFIG_LEGACY_HW and on others, the macro can be left undefined, so
> that any attempt to compile drivers requiring legacy hw would fail to
> compile upfront (much better than accessing random ports!).

Yes, that looks very good indeed. Riley?

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR
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