* Re: kbuild: default n removals? (was: Re: [PATCH v3 4/6] watchdog: add watchdog pretimeout framework)
2016-06-08 15:38 ` kbuild: default n removals? (was: Re: [PATCH v3 4/6] watchdog: add watchdog pretimeout framework) Joe Perches
@ 2016-06-08 18:05 ` Guenter Roeck
2016-06-15 10:02 ` kbuild: default n removals? Michal Marek
1 sibling, 0 replies; 3+ messages in thread
From: Guenter Roeck @ 2016-06-08 18:05 UTC (permalink / raw)
To: Joe Perches
Cc: Vladimir Zapolskiy, Michal Marek, Wim Van Sebroeck, Wolfram Sang,
Robin Gong, linux-watchdog, linux-kernel, linux-kbuild
On Wed, Jun 08, 2016 at 08:38:52AM -0700, Joe Perches wrote:
> (Adding Michal Marek and linux-kbuild)
>
> On Wed, 2016-06-08 at 18:11 +0300, Vladimir Zapolskiy wrote:
> > On 08.06.2016 16:53, Guenter Roeck wrote:
> > > On 06/08/2016 06:37 AM, Vladimir Zapolskiy wrote:
> > > > > > +comment "Watchdog Pretimeout Governors"
> > > > > > +
> > > > > > +config WATCHDOG_PRETIMEOUT_GOV
> > > > > > + bool "Enable watchdog pretimeout governors"
> > > > > > + default n
> > > > > I don't think 'default n" is needed.
> > > > >
> > > > No strict objections, but probably 'default n' may save quite many
> > > > lines in defconfigs.
> > > >
> > > I always wondered why it would be necessary to say "default n".
> > > What is the difference between "default n" and no explicit default ?
> > >
> > I pointed out that it may have impact on defconfig, but experimentally
> > it has no effect.
> >
> > Users of "make oldconfig" get a prompt in both cases as well.
> >
> > Also I haven't found any difference for silentoldconfig, olddefconfig
> > and alldefconfig, I assume explicit "default n" and "def_bool n"
> > can be safely dropped.
>
> It's not completely clear removals are always appropriate.
>
> from: Documentation/kbuild/kconfig-language.txt:
> ------------------------------------------------------------------
> - default value: "default" <expr> ["if" <expr>]
> A config option can have any number of default values. If multiple
> default values are visible, only the first defined one is active.
> Default values are not limited to the menu entry where they are
> defined. This means the default can be defined somewhere else or be
> overridden by an earlier definition.
> The default value is only assigned to the config symbol if no other
> value was set by the user (via the input prompt above). If an input
> prompt is visible the default value is presented to the user and can
> be overridden by him.
> Optionally, dependencies only for this default value can be added with
> "if".
This describes default settings such as
default n if <expr>
default y
which would set the default to y unless <expr> is true.
Question here was about the stand-alone "default n" which always
perplexed me.
Guenter
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: kbuild: default n removals?
2016-06-08 15:38 ` kbuild: default n removals? (was: Re: [PATCH v3 4/6] watchdog: add watchdog pretimeout framework) Joe Perches
2016-06-08 18:05 ` Guenter Roeck
@ 2016-06-15 10:02 ` Michal Marek
1 sibling, 0 replies; 3+ messages in thread
From: Michal Marek @ 2016-06-15 10:02 UTC (permalink / raw)
To: Joe Perches
Cc: Vladimir Zapolskiy, Guenter Roeck, Wim Van Sebroeck, Wolfram Sang,
Robin Gong, linux-watchdog, linux-kernel, linux-kbuild
On 2016-06-08 17:38, Joe Perches wrote:
> (Adding Michal Marek and linux-kbuild)
>
> On Wed, 2016-06-08 at 18:11 +0300, Vladimir Zapolskiy wrote:
>> On 08.06.2016 16:53, Guenter Roeck wrote:
>>> On 06/08/2016 06:37 AM, Vladimir Zapolskiy wrote:
>>>>>> +comment "Watchdog Pretimeout Governors"
>>>>>> +
>>>>>> +config WATCHDOG_PRETIMEOUT_GOV
>>>>>> + bool "Enable watchdog pretimeout governors"
>>>>>> + default n
>>>>> I don't think 'default n" is needed.
>>>>>
>>>> No strict objections, but probably 'default n' may save quite many
>>>> lines in defconfigs.
>>>>
>>> I always wondered why it would be necessary to say "default n".
>>> What is the difference between "default n" and no explicit default ?
>>>
>> I pointed out that it may have impact on defconfig, but experimentally
>> it has no effect.
>>
>> Users of "make oldconfig" get a prompt in both cases as well.
>>
>> Also I haven't found any difference for silentoldconfig, olddefconfig
>> and alldefconfig, I assume explicit "default n" and "def_bool n"
>> can be safely dropped.
Yes, 'default n' is a noop.
> It's not completely clear removals are always appropriate.
>
> from: Documentation/kbuild/kconfig-language.txt:
> ------------------------------------------------------------------
> - default value: "default" <expr> ["if" <expr>]
> A config option can have any number of default values. If multiple
> default values are visible, only the first defined one is active.
> Default values are not limited to the menu entry where they are
> defined. This means the default can be defined somewhere else or be
> overridden by an earlier definition.
> The default value is only assigned to the config symbol if no other
> value was set by the user (via the input prompt above). If an input
> prompt is visible the default value is presented to the user and can
> be overridden by him.
> Optionally, dependencies only for this default value can be added with
> "if".
> ------------------------------------------------------------------
>
> Michal? Do you have an opinion or clarification?
As Guenter explained, there can be multiple default statements with
different if conditions. The first statement to match applies.
Michal
^ permalink raw reply [flat|nested] 3+ messages in thread