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Date: Fri, 24 Sep 2010 15:57:13 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Richard Cochran <richardcochran@gmail.com>
Cc: john stultz <johnstul@us.ibm.com>, linux-kernel@vger.kernel.org,
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        Peter Zijlstra <peterz@infradead.org>,
        Rodolfo Giometti <giometti@linux.it>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v6 0/8] ptp: IEEE 1588 hardware clock support
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> > Instead, I think having the id hanging off the class driver is much
> > better, as it allows mapping the actual hardware to the id more clearly.
> > 
> > So I'd drop the "timesource" listing. And maybe change "id" to
> > "clock_id" so its a little more clear what the id is for.
> 
> Okay, I will drop /sys/class/timesource (hope Alan Cox agrees :)

It makes sense to hang anything off the physical id

> I threw it out there mostly for the sake of discussion. I imagined
> that there could be other properties in that directory, like time
> scale (TAI, UTC, etc). But it seems like we don't really need anything
> in that direction.

They can still hang off the physical device. Thats really a detail

> > interrupts are awfully frequent, so systems concerned with power-saving
> > and deep idles probably would like something that could be done at a
> > more coarse interval.
> 
> We could always make the pulse rate programmable, for power-saving
> applications.

I would expect the kernel drivers to be responsible for
- Turning off when they can
- Picking rates that are power optimal for the requirement

The latter is a bit interesting as I don't see anything in any of the
timer APIs to express accuracy (a problem we have in kernel too).
Historically it simply hasn't mattered.