Mutli-directory module Makefiles

Mutli-directory module Makefiles

[Jakub Kicinski]

Hi!

in drivers/net/ethernet/netronome/nfp there is a module which is built
from C sources in 4 directories.  What is the best way to handle that?

Currently we just add all the objects in one Makefile:

nfp-objs := \
	    nfpcore/nfp6000_pcie.o \
	    nfpcore/nfp_cppcore.o \
etc.

However, this makes it impossible to build a single object in subdirs:

$ make drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.o
scripts/Makefile.build:45: drivers/net/ethernet/netronome/nfp/nfpcore/Makefile: No such file or directory
make[2]: *** No rule to make target 'drivers/net/ethernet/netronome/nfp/nfpcore/Makefile'. Stop.

Documentation/kbuild/modules.txt also contains an unclear remark that
this is not recommended (or is it about the use of $(src)?):

--- 4.3 Several Subdirectories
	...
	To build the module complex.ko, we then need the following
	kbuild file:

		--> filename: Kbuild
		obj-m := complex.o
		complex-y := src/complex_main.o
		complex-y += src/hal/hardwareif.o

		ccflags-y := -I$(src)/include
		ccflags-y += -I$(src)/src/hal/include

	As you can see, kbuild knows how to handle object files located
	in other directories. The trick is to specify the directory
	relative to the kbuild file's location. **That being said, this
	is NOT recommended practice.**

Making the include optional would work:

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
@@ -42,7 +42,7 @@ save-cflags := $(CFLAGS)
 # The filename Kbuild has precedence over Makefile
 kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
 kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
-include $(kbuild-file)
+-include $(kbuild-file)
 
 # If the save-* variables changed error out
 ifeq ($(KBUILD_NOPEDANTIC),)

Or we could create empty Makefiles in subdirectories...  Is there a
better way of handling this?  Which is preferred?

Re: Mutli-directory module Makefiles

[Masahiro Yamada]

2018-01-23 6:46 GMT+09:00 Jakub Kicinski <kubakici@wp.pl>:
> Hi!
>
> in drivers/net/ethernet/netronome/nfp there is a module which is built
> from C sources in 4 directories.  What is the best way to handle that?
>
> Currently we just add all the objects in one Makefile:
>
> nfp-objs := \
>             nfpcore/nfp6000_pcie.o \
>             nfpcore/nfp_cppcore.o \
> etc.


I recommend you to refactor the Makefile,
adding Makefiles into nfpcore, nic, flower, bpf sub-directories.


Also, ifeq is ugly,
can you rewrite like follows?


nfp-$(CONFIG_NFP_APP_FLOWER)    += flower/
nfp-$(CONFIG_BPF_SYSCALL)       += bpf/
nfp-$(CONFIG_NFP_DEBUG)         += nfp_net_debugfs.o





> However, this makes it impossible to build a single object in subdirs:
>
> $ make drivers/net/ethernet/netronome/nfp/nfpcore/nfp_cppcore.o
> scripts/Makefile.build:45: drivers/net/ethernet/netronome/nfp/nfpcore/Makefile: No such file or directory
> make[2]: *** No rule to make target 'drivers/net/ethernet/netronome/nfp/nfpcore/Makefile'. Stop.
>
> Documentation/kbuild/modules.txt also contains an unclear remark that
> this is not recommended (or is it about the use of $(src)?):
>
> --- 4.3 Several Subdirectories
>         ...
>         To build the module complex.ko, we then need the following
>         kbuild file:
>
>                 --> filename: Kbuild
>                 obj-m := complex.o
>                 complex-y := src/complex_main.o
>                 complex-y += src/hal/hardwareif.o
>
>                 ccflags-y := -I$(src)/include
>                 ccflags-y += -I$(src)/src/hal/include
>
>         As you can see, kbuild knows how to handle object files located
>         in other directories. The trick is to specify the directory
>         relative to the kbuild file's location. **That being said, this
>         is NOT recommended practice.**
>
> Making the include optional would work:
>
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> @@ -42,7 +42,7 @@ save-cflags := $(CFLAGS)
>  # The filename Kbuild has precedence over Makefile
>  kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
>  kbuild-file := $(if $(wildcard $(kbuild-dir)/Kbuild),$(kbuild-dir)/Kbuild,$(kbuild-dir)/Makefile)
> -include $(kbuild-file)
> +-include $(kbuild-file)
>
>  # If the save-* variables changed error out
>  ifeq ($(KBUILD_NOPEDANTIC),)
>
> Or we could create empty Makefiles in subdirectories...  Is there a
> better way of handling this?  Which is preferred?



-- 
Best Regards
Masahiro Yamada

Re: Mutli-directory module Makefiles

[Jakub Kicinski]

On Thu, 25 Jan 2018 22:08:34 +0900, Masahiro Yamada wrote:
> 2018-01-23 6:46 GMT+09:00 Jakub Kicinski <kubakici@wp.pl>:
> > Hi!
> >
> > in drivers/net/ethernet/netronome/nfp there is a module which is built
> > from C sources in 4 directories.  What is the best way to handle that?
> >
> > Currently we just add all the objects in one Makefile:
> >
> > nfp-objs := \
> >             nfpcore/nfp6000_pcie.o \
> >             nfpcore/nfp_cppcore.o \
> > etc.  
> 
> 
> I recommend you to refactor the Makefile,
> adding Makefiles into nfpcore, nic, flower, bpf sub-directories.
> 
> 
> Also, ifeq is ugly,
> can you rewrite like follows?
> 
> 
> nfp-$(CONFIG_NFP_APP_FLOWER)    += flower/
> nfp-$(CONFIG_BPF_SYSCALL)       += bpf/
> nfp-$(CONFIG_NFP_DEBUG)         += nfp_net_debugfs.o

I tried that, but what do I build inside the directories?  I tried
adding the objects to nfp-objs, building a lib.a, or trying to build a
separate object, but it's either ignored or dependency is not obeyed
and nfp.o complains that the subdirectory object doesn't exist yet
when the build of subdirectory finishes later :(

Sorry for not spotting your response earlier!  It went into Spam for
some reason :S

Re: Mutli-directory module Makefiles

[Masahiro Yamada]

2018-01-26 4:47 GMT+09:00 Jakub Kicinski <kubakici@wp.pl>:
> On Thu, 25 Jan 2018 22:08:34 +0900, Masahiro Yamada wrote:
>> 2018-01-23 6:46 GMT+09:00 Jakub Kicinski <kubakici@wp.pl>:
>> > Hi!
>> >
>> > in drivers/net/ethernet/netronome/nfp there is a module which is built
>> > from C sources in 4 directories.  What is the best way to handle that?
>> >
>> > Currently we just add all the objects in one Makefile:
>> >
>> > nfp-objs := \
>> >             nfpcore/nfp6000_pcie.o \
>> >             nfpcore/nfp_cppcore.o \
>> > etc.
>>
>>
>> I recommend you to refactor the Makefile,
>> adding Makefiles into nfpcore, nic, flower, bpf sub-directories.
>>
>>
>> Also, ifeq is ugly,
>> can you rewrite like follows?
>>
>>
>> nfp-$(CONFIG_NFP_APP_FLOWER)    += flower/
>> nfp-$(CONFIG_BPF_SYSCALL)       += bpf/
>> nfp-$(CONFIG_NFP_DEBUG)         += nfp_net_debugfs.o
>
> I tried that, but what do I build inside the directories?  I tried
> adding the objects to nfp-objs, building a lib.a, or trying to build a
> separate object, but it's either ignored or dependency is not obeyed
> and nfp.o complains that the subdirectory object doesn't exist yet
> when the build of subdirectory finishes later :(
>
> Sorry for not spotting your response earlier!  It went into Spam for
> some reason :S
>

Sorry, I was misunderstanding.

The notation I suggested
is not supported for composite objects (like nfp-objs, nfp-y).

The only solution is to move all files to the same directory,
as Sam pointed out.




-- 
Best Regards
Masahiro Yamada

Re: Mutli-directory module Makefiles

[Sam Ravnborg]

Hi Jakub.

On Mon, Jan 22, 2018 at 01:46:07PM -0800, Jakub Kicinski wrote:
> Hi!
> 
> in drivers/net/ethernet/netronome/nfp there is a module which is built
> from C sources in 4 directories.  What is the best way to handle that?

Move all .c files to th same directory - like done for almost
all other drives.
In this case we have a directory: drivers/net/ethernet/netronome
which is just an indirection to nfp/
and nfp/ contains a structure with 25 .c files in subdirs.

With some careful renaming everything could reside in
one dir without loosing any structure.
And then the driver starts to look a bit
more like any other driver in the kernel.

And as an added benefit some of the other goodies like
building single files just works.

	Sam