linux-kernel - Re: [PATCH v2] clockevents: Introduce mode specific callbacks

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Message-ID: <1757256.KD83W4bJsz@vostro.rjw.lan>
Date:	Fri, 13 Feb 2015 15:46:11 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...aro.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Linaro Networking <linaro-networking@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] clockevents: Introduce mode specific callbacks

On Friday, February 13, 2015 11:01:18 AM Viresh Kumar wrote:
> On 13 February 2015 at 10:11, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > On Friday, February 13, 2015 08:54:56 AM Viresh Kumar wrote:
> >> It is not possible for the clockevents core to know which modes (other than
> >> those with a corresponding feature flag) are supported by a particular
> >> implementation. And drivers are expected to handle transition to all modes
> >> elegantly, as ->set_mode() would be issued for them unconditionally.
> >>
> >> Now, adding support for a new mode complicates things a bit if we want to use
> >> the legacy ->set_mode() callback. We need to closely review all clockevents
> >> drivers to see if they would break on addition of a new mode. And after such
> >> reviews, it is found that we have to do non-trivial changes to most of the
> >> drivers [1].
> >>
> >> Introduce mode-specific set_mode_*() callbacks, some of which the drivers may or
> >> may not implement. A missing callback would clearly convey the message that the
> >> corresponding mode isn't supported.
> >
> > This is not going to fly AFAICS if you don't say what exacly you need it for.
> 
> For this: https://lkml.org/lkml/2014/5/9/508

OK, I see.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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