Arnd Bergmann <arnd@xxxxxxxx> a écrit :
On Sat, Dec 29, 2018 at 3:51 AM Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
Hi Finn,
Am 29.12.2018 um 15:34 schrieb Finn Thain:
> On Sat, 29 Dec 2018, Michael Schmitz wrote:
>
>>
>> IS_BUILTIN(CONFIG_NVRAM) is probably what Christophe really
meant to suggest.
>>
>> Or (really going out on a limb here):
>>
>> IS_BUILTIN(CONFIG_NVRAM) ||
>> ( IS_MODULE(CONFIG_ATARI_SCSI) && IS_ENABLED(CONFIG_NVRAM) )
>>
>> Not that I'd advocate that, for this series.
>>
>
> Well, you are a maintainer for atari_scsi.c.
>
> Are you saying that you want IS_BUILTIN(CONFIG_NVRAM) used here instead of
> ifdef?
No, just pointing out that there would be a way to avoid the ifdef
without messing up driver behaviour. I'm fine with the ifdef - not least
because it clearly eliminates code that would be unreachable.
(On second thought - I don't want to speculate whether there's weird
compiler options that could result in the nvram_check_checksum and
nvram_read_bytes symbols to still be referenced in the final link, even
though IS_BUILTIN(CONFIG_NVRAM) always evaluates to false. Best leave
this as-is.)
As far as I know, it's totally reliable with the supported compilers
(gcc-4.6+).
In the older compilers (e.g. 4.1), there was a corner case, where it could
have failed to eliminate a function that was only referenced through
a pointer
from a discarded variable, but a plain IS_ENABLED() check like the one here
was still ok, and lots of code relies on that.
Other than that, I agree either way is totally fine here, so no objections
to using the #ifdef.
As far as I know, kernel codying style promotes the use of
IS_ENABLED() etc. instead of #ifdefs when possible.
Christophe
Arnd
