Hi, On 10/29/20 3:16 PM, Coiby Xu wrote: > On Thu, Oct 29, 2020 at 12:09:23PM +0100, Hans de Goede wrote: >> Hi, >> >> On 10/29/20 11:59 AM, Coiby Xu wrote: >>> Hi Hans, >>> >>> Thank you for reviewing this patch! >>> >>> On Thu, Oct 29, 2020 at 11:04:36AM +0100, Hans de Goede wrote: >>>> Hi, >>>> >>>> On 10/29/20 8:41 AM, Coiby Xu wrote: >>>>> SIMPLE_DEV_PM_OPS has already took good care of CONFIG_PM_CONFIG. >>>> >>>> No it does not, when CONFIG_PM_SLEEP is not set then the >>>> SET_SYSTEM_SLEEP_PM_OPS macro which SIMPLE_DEV_PM_OPS uses >>>> is a no-op, so nothing will reference xo15_sci_resume leading to >>>> a compiler warning when CONFIG_PM_SLEEP is not set. >>>> >>>> You could drop the ifdef and add __maybe_unused to the definition >>>> of xo15_sci_resume, but that feels like needless churn, best to >>>> just keep this as is IMHO. >>>> >>> >>> Actually, this is a tree-wide change by some semi-automation scripts. >>> Thank you for pointing out the issue to prevent me from releasing >>> another ~150 emails to flood other mailing lists. >>> >>> Currently there are 929 drivers has device PM callbacks, >>> >>> $ grep -rI "\.pm = &" --include=*.c ./|wc -l >>> 929 >>> >>> I put all files having device PM callbacks into four categories >>> based on weather a file has CONFIG_PM_SLEEP or PM macro like >>> SET_SYSTEM_SLEEP_PM_OPS, here are the statistics, >>>  1. have both CONFIG_PM_SLEEP and PM_OPS macro: 213 >>>  2. have CONFIG_PM_SLEEP but no PM_OPS macro: 19 >>>  3. have PM macro but not CONFIG_PM_SLEEP: 347 >>>  4. no PM macro or CONFIG_PM_SLEEP: 302 >>> >>> Some drivers which have PM macro but not CONFIG_PM_SLEEP like >>> sound/x86/intel_hdmi_audio.c indeed use __maybe_unused to eliminate >>> the compiling warning. In 2011, there's a patch proposing to remove >>> ONFIG_PM altogether but an objection was turning CONFIG_PM on would >>> increase the kernel size [1]. So __maybe_unused also have this issue. >> >> I would expect the compiler to remove the unused function, it knows >> it is unused, that is why __maybe_unused is necessary to suppress >> the warning and compilers are pretty smart and agressive wrt remove >> unnecessary code these days. >> > Then __maybe_unused is a good solution and there's also convincing > reason to prefer __maybe_unused over CONFIG_PM_SLEEP according to > Arnd Bergmann [2], Ok, I would be happy to merge a patch for this which drops the #ifdef-s and adds a __maybe_unused. Regards, Hans
