On 08/08/2017 04:28 AM, Peter Zijlstra wrote:
> On Mon, Aug 07, 2017 at 01:36:39PM -0700, Paul E. McKenney wrote:
>> On Mon, Aug 07, 2017 at 04:06:09PM -0400, Prarit Bhargava wrote:
>
>>> peterz? Want to offer a suggestion? The issue is that I'm changing a bool
>>> config option to an int and that impacts all the arch's defconfigs. John
>>> points
>>> out that this is a lot of churn and we're both wondering if there's a
>>> better way
>>> to do the configs.
>>
>> The usual approach is to keep the old bool Kconfig option, and add another
>> int Kconfig option that depends on the original one. The tests for
>> the int value get a bit more complex, but one way to handle this is to
>> define a cpp macro something like the following:
>>
>> #ifdef CONFIG_OLD_OPTION
>> #define CPP_NEW_OPTION 0
>> #else
>> #define CPP_NEW_OPTION CONFIG_NEW_OPTION
>> #endif
>>
>> Then use CPP_NEW_OPTION, where zero means disabled and other numbers
>> select the available options.
>>
>> Adjust to suit depending on what values mean what.
>>
>> Another approach is to make the range of the new Kconfig option
>> depend on the old option:
>>
>> config NEW_OPTION
>> int "your description here"
>> range 1 5 if OLD_OPTION
>> range 0 0 if !OLD_OPTION
>> default 0
>> help
>> your help here
>>
>> Again, adjust to suit depending on what values mean what.
>
> Right this. Except I don't see the !OLD_OPTION working as expected.
> A 'new' config will not include the old one, so the !OLD_OPTION thing
> will 'always' be true.
>
> So your:
>
>> @@ -1,8 +1,46 @@
>> menu "printk and dmesg options"
>>
>> +choice
>> + prompt "printk default clock"
>> + config PRINTK_TIME_DISABLE
>> + bool "Disabled"
>> + help
>> + Selecting this option disables the time stamps of printk().
>> +
>> + config PRINTK_TIME_LOCAL
>> + bool "Local Clock"
>> + help
>> + Selecting this option causes the time stamps of printk() to be
>> + stamped with the unadjusted hardware clock.
>> +
>> + config PRINTK_TIME_BOOT
>> + bool "CLOCK_BOOTTIME"
>> + help
>> + Selecting this option causes the time stamps of printk() to be
>> + stamped with the adjusted boottime clock.
>> +
>> + config PRINTK_TIME_MONO
>> + bool "CLOCK_MONOTONIC"
>> + help
>> + Selecting this option causes the time stamps of printk() to be
>> + stamped with the adjusted monotonic clock.
>> +
>> + config PRINTK_TIME_REAL
>> + bool "CLOCK_REALTIME"
>> + help
>> + Selecting this option causes the time stamps of printk() to be
>> + stamped with the adjusted realtime clock.
>> +
>> +endchoice
>> +
>> config PRINTK_TIME
>
> Change that into something like:
>
> config PRINTK_CLOCK
>
>
>> - bool "Show timing information on printks"
>> + int "Show time stamp information on printks"
>> depends on PRINTK
>> + default 0 if PRINTK_TIME_DISABLE
>> + default 1 if PRINTK_TIME_LOCAL
>
> And that into:
>
> default 1 if PRINTK_TIME_LOCAL || PRINTK_TIME
>
>> + default 2 if PRINTK_TIME_BOOT
>> + default 3 if PRINTK_TIME_MONO
>> + default 4 if PRINTK_TIME_REAL
>> help
>> Selecting this option causes time stamps of the printk()
>
> Then the old PRINTK_TIME symbol will auto-convert into the new
> equivalent.
>
I don't think there's an easy code way around this. Essentially this Kconfig
code boils down to properly evaluating
config PRINTK_CLOCK
default 1 if PRINTK_TIME
default 0
where there is no Kconfig entry for PRINTK_TIME.
If undefined CONFIG_PRINTK_TIME is used in a config, it is immediately
scrubbed by the kconfig script so it doesn't "exist" when CONFIG_PRINTK_CLOCK
is evaluated. The result of that is CONFIG_PRINT_CLOCK=0.
I tried
config PRINTK_TIME
bool "old config option"
then I end up with both a CONFIG_PRINTK_CLOCK=1 and a CONFIG_PRINTK_TIME=y in
the resulting config which is confusing.
I've debated using the other suggestion that Paul made but TBH (sorry
Paul) it seems like I'm avoiding the real but noisy solution of
s/PRINTK_TIME=y/PRINTK_TIME=1/g
I'm obviously open to other suggestions...
P.
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