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

Peter Feuerer
2014-07-22T15:04:25Z

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@linux-foundation.org>
>> > Cc: Zhang Rui <rui.zhang@intel.com>
>> > Cc: Andreas Mohr <andi@lisas.de>
>> > Cc: Borislav Petkov <bp@suse.de>
>> > Cc: Javi Merino <javi.merino@arm.com>
>> > Signed-off-by: Peter Feuerer <peter@piie.net>
>> > ---
>> > 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;