Re: [Buildroot] Building packages for Cortex M4

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Andrey, All,

On 2021-12-13 18:36 +0100, Andrey Nechypurenko spake thusly:
> On Sat, 11 Dec 2021 at 09:35, Arnout Vandecappelle <arnout@mind.be> wrote:
> > On 09/12/2021 18:02, Andrey Nechypurenko wrote:
[--SNIP--]
> > > comcu.mk:
> > >
> > > ################################################################################
> > > #
> > > ## comcu
> > > #
> > > #################################################################################
> > >
> > > COMCU_SITE = $(TOPDIR)/../src/comcu
> > > COMCU_SITE_METHOD = local
> > >
> > > COMCU_CONF_OPTS = \
> > >      -DTOOLCHAIN_DIR=$(HOST_DIR)/share/gcc-arm-none-eabi \
> > >      -DCMAKE_TOOLCHAIN_FILE=cmake/TOOLCHAIN_arm_none_eabi_cortex_m4.cmake \
> > >      -DUSE_HAL_DRIVER=ON \
> > >      -DUSE_LL_DRIVER=OFF \
> > >      -DUSE_OPENAMP=ON \
> > >      -DUSE_STM32_USB_FS_LIB=OFF \
> > >      -DUSE_FREERTOS=OFF \
> > >      -DUSE_SEMIHOSTING=OFF \
> > >      -DUSE_STTERM=OFF \
> > >      -DUSE_DBGUART=OFF \
> > >      -DUSE_GDB=OFF \
> > >      -DUSE_OVERCLOCKING=OFF \
> > >      -DUSE_TINY_PRINTF=OFF \
> > >      -DSRC=Src \
> > >      -DGITHUB_DRIVERS=OFF
> > >
> > > $(eval $(cmake-package))
> >
> >   I wonder if we really want to use cmake-package here... The cmake-package
> > infrastructure is geared towards building for the target, not for some other
> > CPU. The fact that you need to override the toolchain file is indicative of this
> > problem.
> 
> Could you please elaborate on it a little bit? My understanding is that
> independent of what build-system (cmake or whatever else) is used, somehow
> you need to say that other toolchain should be used to compile particular
> package. CMake's way of doing it is to use the toolchain file. Somehow I can
> not see any big disadvantages with it. Similarly I can not see any big
> advantages of using other build-systems. They will need to do the same but
> with different syntax.
> 
> The only reason why I used cmake here is because this is what provided by ST
> as an example. The CMake file is not trivial with all these
> CMSIS/HAL/BSP/Cube/... things. Since I do not see any big advantages from
> using other build system, I can not find enough motivation to spend time on
> converting cmake staff to something different. That is why I would
> appreciate if you can provide more details on why cmake could be a bad idea
> in this case.

What Arnout was wondering about, is not about using cmake or not; it was
about using the cmake-package infrastructure in Buildroot or not.

I.e., what he was basically suggesting between the lines, was to make
that a generic package, something along the lines of:

    COMCU_DEPENDENCIES = host-cmake

    define COMCU_CONFIGURE_CMDS
        $(BR2_CMAKE) $(@D) \
            -DTOOLCHAIN_DIR=$(HOST_DIR)/share/gcc-arm-none-eabi \
            -DCMAKE_TOOLCHAIN_FILE=cmake/TOOLCHAIN_arm_none_eabi_cortex_m4.cmake \
            [etc...]
    endef

    define COMCU_BUILD_CMDS
        $(MAKE) -C $(@D)
    endef

    define COMCU_INSTALL_TARGET_CMDS
        $(MAKE) -C $(@D) DESTDIR=$(TARGET_DIR) install/fast
    endef

    $(eval $(generic-package))

And I do agree with him, in that our cmake infra is made only for
building stuff that runs on the architecture that is defined in
Buildroot's configuration, not to build firmwares that run in add-on
CPUs...

However, I can also see that the way you did it also makes the package
drastically simpler that repeating a good part of the cmake-package
infra, so I am a bit torn...

 would still think that it would be better to do a generic-package,
because the cmake-pakcage infra can very well get additional "features"
that would render it unusable for using with another toolchain file.
And I would like to avoid introducing a precedent...

So I'm back with Arnout: make that a generic-package.

Regards,
Yann E. MORIN.

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