Messages in this thread | | | Date | Fri, 12 Dec 2008 16:18:38 +0900 | From | "Magnus Damm" <> | Subject | Re: [PATCH] clocksource: add enable() and disable() callbacks |
| |
Hi Ingo,
On Fri, Dec 12, 2008 at 3:36 PM, Ingo Molnar <mingo@elte.hu> wrote: > * Magnus Damm <magnus.damm@gmail.com> wrote: >> +static inline int clocksource_enable(struct clocksource *cs) >> +{ >> + return cs->enable ? cs->enable(cs) : 0; >> +} > >> +static inline void clocksource_disable(struct clocksource *cs) >> +{ >> + if (cs->disable) >> + cs->disable(cs); >> +} > > why have the two different styles? The first one should be: > > if (cs->enable) > return cs->enable(cs); > return 0;
Sure, that's fine too.
>> @@ -193,11 +193,16 @@ static void change_clocksource(void) >> >> clocksource_forward_now(); >> >> - new->raw_time = clock->raw_time; >> + if (clocksource_enable(new)) >> + return; > > that looks fragile to me: if the enable fails we'll return silently, > while change_clocksource() assumes that things went fine. At least put a > WARN_ON_ONCE() in there.
Yeah, John and I discussed this before. What we really want it to move the failing clocksource out of the list of available clocksources. That type of change is pretty intrusive though, and I rather see it as a separate topic.
> also, why does it have to fail? If a clocksource cannot be enabled it > should not be offered as a clocksource.
Right. I guess most clocksource drivers for embedded platforms will tie in the clock framework and use clk_enable() and clk_disable(). clk_enable() returns an int.
>> + clocksource_disable(old); > > i do agree with the core purpose here, to allow lowlevel code to > deactivate unused clocksources.
That's good! I hope we can sort out the details then!
Cheers,
/ magnus
| |