Re: [PATCH] Documentation: kbuild: Add note about using (subst m,y)

[Alexander Lobakin]

From: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date: Tue, 28 Feb 2023 17:30:09 +0900

> On Tue, Feb 28, 2023 at 12:13 PM David Gow <davidgow@xxxxxxxxxx> wrote:

[...]

>> +Example::
>> +
>> +  #drivers/Makefile
>> +  obj-$(subst m,y,$(CONFIG_HYPERV)) += hv/
>> +
> 
> 
> I think many subsystems simply do
> 
> obj-y  += hv/

This creates a ton of empty built-in.a, each of them is listed in the
Kbuild output. Someone may think that if a directory contains
built-in.a, then something was built there. Sure it's their problems,
but I'd prefer to not pollute the log and built-in.a contents when
possible (empty files are still listed there IIRC).

> 
> 
> I do not think we need to advertise hyperv's way
> since it does not look very pretty.
> 
> 
> 
> 
> 
> 
> 
> Mostly, it looks like this:
> 
> 
> obj-y  += kunit/
> 
> and
> 
> obj-$(CONFIG_KUNIT_HOOK)   += hook.o
> 
> 
> 
> 
> 
> 
> 
> Bikeshed:
> 
> I think Linus' suggestion is OK, but
> the BSD style seems less ugly,
> of course, that is just a matter of style.
> 
> 
> obj-$(CONFIG_HYPERV:m=y)   += kunit/

I'd vote for this one, it's compact and readable.

> 
> 
> 
> 
>>  Kbuild also supports dedicated syntax, subdir-y and subdir-m, for
>>  descending into subdirectories. It is a good fit when you know they
>>  do not contain kernel-space objects at all. A typical usage is to let
>> --
>> 2.39.2.722.g9855ee24e9-goog
>>
> 
> 
> --
> Best Regards
> Masahiro Yamada
> 

Thanks,
Olek