How to build an external module in a specified directory?

[Alexander Kapshuk]

On Tue, Jan 3, 2017 at 4:11 PM, Alexander Kapshuk
<alexander.kapshuk at gmail.com> wrote:
> On Tue, Jan 3, 2017 at 9:32 AM, Shiyao Ma <i at introo.me> wrote:
>> Hi Alexander,
>>
>>
>> Looking at that Makefile:
>>
>> # Use make M=dir to specify directory of external module to build
>> # Old syntax make ... SUBDIRS=$PWD is still supported
>> # Setting the environment variable KBUILD_EXTMOD take precedence
>> ifdef SUBDIRS
>>   KBUILD_EXTMOD ?= $(SUBDIRS)
>> endif
>>
>> ifeq ("$(origin M)", "command line")
>>   KBUILD_EXTMOD := $(M)
>> endif
>>
>>
>> So specifying KBUILD_EXTMOD or M is the same thing, which tells KBUILD the
>> directory that the Makefile for the module is in.
>> And by default, KBUILD will build the module in KBUILD_EXTMOD.
>>
>> What I want is tell KBUILD to build the modules in a specified directory.
>>
>>
>>
>> Regards.
>>
>>
>>
>>
>>
>> On Jan 2, 2017, 20:30 +0800, Alexander Kapshuk
>> <alexander.kapshuk at gmail.com>, wrote:
>>
>> On Mon, Jan 2, 2017 at 1:39 PM, Shiyao Ma <i at introo.me> wrote:
>>
>> Hi,
>>
>> When building an external module, for example, given this command,
>> all:
>> $(MAKE) -C $(KDIR) M=$$PWD
>>
>> It will build the ko file in the $PWD.
>>
>> How to specify a location for the .ko files?
>>
>>
>> Regards.
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
>>
>> Perhaps KBUILD_EXTMOD is what you're looking for.
>>
>> /path/to/kernel/sources/Makefile:183,185
>> # Use make M=dir to specify directory of external module to build
>> # Old syntax make ... SUBDIRS=$PWD is still supported
>> # Setting the environment variable KBUILD_EXTMOD take precedence
>
> I haven't verified this, but perhaps KBUILD_OUTPUT would better server
> your purposes.
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/plain/Documentation/kbuild/kbuild.txt?id=refs/tags/v4.10-rc2
> KBUILD_OUTPUT
> --------------------------------------------------
> Specify the output directory when building the kernel.
> The output directory can also be specified using "O=...".
> Setting "O=..." takes precedence over KBUILD_OUTPUT.

Tain't it either. Just verified it on my system.

Don't have an answer for you at the moment. Sorry.