Re: [PATCH RFC 5/6] drm/tilcdc: Force building of DRM_TILCDC_INIT

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 26/02/15 16:55, Jyri Sarha wrote:
> If I read Documentation/kbuild/makefiles.txt section 3.6 right, this
> patch should not be needed. However, without this patch the objects
> needed for DRM_TILCDC_INIT are not linked, if DRM_TILCDC is built as
> module.

I also think there's something funny either with the documentation or
the kernel build system.

To summarize (Jyri correct me if I'm wrong):

We enter tilcdc directory using "obj-$(CONFIG_DRM_TILCDC)", and
CONFIG_DRM_TILCDC is either y or m. Inside the directory we have the
necessary makefile and code to build the driver as module or built-in.
And this works fine.

But now Jyri added new piece of code to tilcdc directory, which is
always built-in, even if the tilcdc driver itself is a module. So now if
we enter the directory with "obj-m", and inside the tilcdc/Makefile we
do "obj-y += foo.o" line, the result is that foo.o is compiled, but it
is not linked either to the kernel image nor to the tilcdc.ko.

The doc says:

"Kbuild only uses this information to decide that it needs to visit
the directory, it is the Makefile in the subdirectory that
specifies what is modular and what is built-in."

which doesn't seem to work for us.

> Signed-off-by: Jyri Sarha <jsarha@ti.com>
> ---
>  drivers/gpu/drm/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 2c239b9..62c6158 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -60,6 +60,7 @@ obj-$(CONFIG_DRM_RCAR_DU) += rcar-du/
>  obj-$(CONFIG_DRM_SHMOBILE) +=shmobile/
>  obj-$(CONFIG_DRM_OMAP)	+= omapdrm/
>  obj-$(CONFIG_DRM_TILCDC)	+= tilcdc/
> +obj-$(CONFIG_DRM_TILCDC_INIT)	+= tilcdc/
>  obj-$(CONFIG_DRM_QXL) += qxl/
>  obj-$(CONFIG_DRM_BOCHS) += bochs/
>  obj-$(CONFIG_DRM_MSM) += msm/

I don't think the above is right. You add two rules for tilcdc
directory. I presume you meant to replace the current tilcdc line with
the new one?

But I don't think the new line makes sense. Using
obj-$(CONFIG_DRM_TILCDC) above makes sense, and also obj-y makes sense,
but obj-$(CONFIG_DRM_TILCDC_INIT) doesn't.

So I think it should be just obj-y, if obj-$(CONFIG_DRM_TILCDC) does not
work.

 Tomi



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