Re: [PATCH v4 3/6] thermal: Added Bang-bang thermal governor

[Peter Feuerer]

Hi,

Zhang Rui writes:

> On Mon, 2014-07-21 at 11:29 +0200, Borislav Petkov wrote:
> > On Sun, Jul 20, 2014 at 02:51:17AM +0200, Peter Feuerer wrote:
> > > The bang-bang thermal governor uses a hysteresis to switch abruptly on
> > > or off a cooling device.  It is intended to control fans, which can
> > > not be throttled but just switched on or off.
> > > Bang-bang cannot be set as default governor as it is intended for
> > > special devices only.  For those special devices the driver needs to
> > > explicitely request it.
> > > 
> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
> > > Cc: Andreas Mohr <andi@xxxxxxxx>
> > > Cc: Borislav Petkov <bp@xxxxxxx>
> > > Cc: Javi Merino <javi.merino@xxxxxxx>
> > > Signed-off-by: Peter Feuerer <peter@xxxxxxxx>
> > > ---
> > >  drivers/thermal/Kconfig         |  10 +++
> > >  drivers/thermal/Makefile        |   1 +
> > >  drivers/thermal/gov_bang_bang.c | 131 ++++++++++++++++++++++++++++++++++++++++
> > >  drivers/thermal/thermal_core.c  |   5 ++
> > >  drivers/thermal/thermal_core.h  |   8 +++
> > >  5 files changed, 155 insertions(+)
> > >  create mode 100644 drivers/thermal/gov_bang_bang.c
> > > 
> > > diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> > > index f9a1386..cdddf09 100644
> > > --- a/drivers/thermal/Kconfig
> > > +++ b/drivers/thermal/Kconfig
> > > @@ -84,6 +84,16 @@ config THERMAL_GOV_STEP_WISE
> > >  	  Enable this to manage platform thermals using a simple linear
> > >  	  governor.
> > >  
> > > +config THERMAL_GOV_BANG_BANG
> > > +	bool "Bang Bang thermal governor"
> > > +	default y
> >
> > Right, this is problematic.
> >
> > When people are faced with the new selection after doing oldconfig, they
> > can say yes or no.
> >
> > However, as acerhdf depends on it now, prompting the user to
> > unconditionally says yes is kinda redundant. Especially as this governor
> > is not supposed to be default anyway.
> >
> > Actually you don't need the Kconfig prompt at all as this is a sort-of
> > "internal" governor and devices select it. IOW, it should be "default n"
> > and ACERHDF will do "select THERMAL_GOV_BANG_BANG". Something like that
> > at least.
> I agree with this approach.

Yes, you are right, this looks better.  Then the "depend on 
THERMAL_GOV_BANG_BANG" could be removed from acerhdf Kbuild, as the "select" 
will take care acerhdf is compiled with THERMAL_GOV_BANG_BANG enabled, 
right?

--
--peter;
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