Re: [PATCH 0/4] media Kconfig reorg - part 2

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

(removed that big c/c list - kept just media)

Em Wed, 25 Mar 2020 16:36:31 -0300
Helen Koike <helen.koike@collabora.com> escreveu:

> Hello,
> 
> On 3/25/20 1:03 PM, Mauro Carvalho Chehab wrote:
> > That's the second part of media Kconfig changes. The entire series is
> > at:
> > 
> > 	https://git.linuxtv.org/mchehab/experimental.git/log/?h=media-kconfig  
> 
> I made a quick experiment (using this branch) with someone who works with the kernel for his master degree, but doesn't have much experience in kernel development in general.
> I asked him to enable Vimc (from default configs, where multimedia starts disabled).
> He knows that Vimc is a virtual camera driver, and this is how he behaved:
> 
> === Start of experiment:
> 
> * He pressed '/' and searched for vimc to see the location path.
> * Then he enabled "Multimedia support" and went straight to "Media drivers" (which just shows USB and PCI).
> * He went back to "Multimedia support", entered "Media device types" and enabled "Test drivers".
> * He went back to "Media drivers" again and didn't find Vimc (nothing changed in this menu).

There was an issue with test driver dependencies. this patch
fixes it:

	https://git.linuxtv.org/mchehab/experimental.git/commit/?h=media-kconfig&id=c267c23e0884172beac4fb4e68c35fc26ff2e615

Basically, the VIDEO_DEV was not selected with MEDIA_TEST_SUPPORT.
So, the "Media drivers" menu would be empty.

After this change, the only thing a .config file would need to build
a test driver would either need to select those:

	CONFIG_MODULES=y
	CONFIG_MEDIA_SUPPORT=m
	CONFIG_MEDIA_SUPPORT_FILTER=y
	CONFIG_MEDIA_TEST_SUPPORT=y
	CONFIG_V4L_TEST_DRIVERS=y
	CONFIG_VIDEO_VIMC=y

	(filtering way)

or those:

	CONFIG_MODULES=y
	CONFIG_MEDIA_SUPPORT=m
	CONFIG_VIDEO_DEV=y
	CONFIG_MEDIA_TEST_SUPPORT=y
	CONFIG_V4L_TEST_DRIVERS=y
	CONFIG_VIDEO_VIMC=y

	(non-filtering way)

(MODULES config is optional. I opted to use modules just to be able
to use make M=drivers/media)

For testing purposes, here, I stored just the above on a file
called media_config, and then I did:

	$ make allnoconfig
	$ cp media_config >.config
	$ make olddefconfig && make init 2>/dev/null
	$ rm $(find drivers/media -name '*.ko') $(find drivers/media -name '*.o') 2>/dev/null
	$ make M=drivers/media
	  CC [M]  drivers/media/common/v4l2-tpg/v4l2-tpg-core.o
	  CC [M]  drivers/media/common/videobuf2/videobuf2-core.o
	  ...
	  MODPOST 8 modules
	  ...
	  LD [M]  drivers/media/v4l2-core/v4l2-dv-timings.ko
	  LD [M]  drivers/media/v4l2-core/videodev.ko

In this specific case, either using the filtered or non-filtered way,
the number of options to enable "vimc" are the same.

Thanks,
Mauro