[PATCH 0/3] drm: Move several files from DRM core into modules

[Thomas Zimmermann]

Hi

Am 21.10.21 um 14:38 schrieb Jani Nikula:
> On Wed, 20 Oct 2021, Thomas Zimmermann <tzimmermann at suse.de> wrote:
>> Move a number of files into modules and behind config options.
>>
>> So far, early boot graphics was provided by fbdev. With simpledrm, and
>> possibly other generic DRM drivers, it's now possible to have general
>> early-boot output with DRM. This requires the DRM core to be linked into
>> the kernel binary image.
>>
>> The reduction in size here is only ~1%, but the patchset is part of a
>> larger effort to reduce the size of the DRM core module.
> 
> I think the main problem is really that of organization. You have all of
> the files under drivers/gpu/drm/ and the only way to know which module
> the files belong to is to look at the Makefile and the Kconfig. It's not
> obvious based on the file names or directory, at all. And there are
> nearly a hundred drm_*.c files there!
> 
> We also seem to have stuff depend on DRM alone, while functionally they
> should really depend on DRM_KMS_HELPER too.

The point of my effort is to have a built-in simpledrm for early-boot 
graphics that requires only a minimal set of built-in dependency. Most 
of the 'advanced' features that native drivers use should go into 
modules. It's a bit unrealistic, but any progress is good.

> 
> The subdirectories under drm/ also don't have any distinction between
> being part of drm core and helpers or drivers. We have lib, scheduler,
> selftests, and ttm next to the drivers.
> 
> We should start adding drm_* subdirectories, and moving the modules
> separate from drm core there. We should rename the current non-driver
> directories drm_*. We need better structure.

Well, there are core functions and helpers. Often, both are in the same 
file and the core 'accidentally' pulls in helpers. For example, I found 
that the core connector automatically creates an EDID property and tries 
to fill in some values, which in turn pulls all the EDID parsing 
helpers. It would be nice to move the parsing code into a module, but 
it's not possible ATM.

For a start we could try to split files into core and helper code and 
link them into different modules.

Best regards
Thomas

> 
> 
> BR,
> Jani.
> 
> 
> 
> 
>>
>> Thomas Zimmermann (3):
>>    drm: Build drm_irq.o only if CONFIG_DRM_LEGACY has been set
>>    drm: Link several object files into drm_kms_helper.ko
>>    drm: Move GEM memory managers into modules
>>
>>   drivers/gpu/drm/Kconfig                |  4 ++--
>>   drivers/gpu/drm/Makefile               | 26 +++++++++++++++-----------
>>   drivers/gpu/drm/drm_gem_cma_helper.c   |  4 ++++
>>   drivers/gpu/drm/drm_gem_shmem_helper.c |  4 ++++
>>   drivers/gpu/drm/drm_irq.c              |  2 --
>>   5 files changed, 25 insertions(+), 15 deletions(-)
>>
>> --
>> 2.33.0
>>
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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