Re: [PATCH] ARM: imx_v6_v7_defconfig: Explicitly restore CONFIG_DEBUG_FS

Leonard Crestez
2019-12-11T19:02:12Z

On 10.12.2019 22:45, Greg Kroah-Hartman wrote:
> On Tue, Dec 10, 2019 at 07:34:20PM +0200, Leonard Crestez wrote:
>> This is currently off and that's not desirable: default imx config is
>> meant to be generally useful for development and debugging.
>>
>> Running git bisect between v5.4 and v5.5-rc1 finds this started from
>> commit 0e4a459f56c3 ("tracing: Remove unnecessary DEBUG_FS dependency")
>>
>> Explicit CONFIG_DEBUG_FS=y was earlier removed by
>> commit c29d541f590c ("ARM: imx_v6_v7_defconfig: Remove unneeded options")
>>
>> A very similar fix was required before:
>> commit 7e9eb6268809 ("ARM: imx_v6_v7_defconfig: Explicitly restore CONFIG_DEBUG_FS")
>>
>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>> ---
>> arch/arm/configs/imx_v6_v7_defconfig | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> Any suggestions to prevent such unexpected kconfig changes in the
>> future? It might make sense for DEBUG_FS to be "default y".
>
> What? No, no system functionality should _EVER_ be dependant on debugfs
> being enabled at all.
>
> If your kernel code requires this, then you are doing something really
> really really wrong.
>
> Now if you just want to have a nice debugging system, then sure, enable
> the option, but it is not anything that should ever be required by any
> working system.

I just want a nice debugging system, my concern is that kconfig rule
adjustments sometimes unexpectedly break this. This issues apparently
also affected shmobile: https://patchwork.kernel.org/patch/11278961/

Config options which can be manually controlled but are also "selected"
from a whole bunch of places can get lost after savedefconfig

Would it be reasonable to make all users "depend on" rather than
"select" DEBUG_FS?

Or perhaps DEBUG_FS could be "default y if DEBUG_KERNEL"?

--
Regards,
Leonard