Re: [PATCH 0/8] drm, fbdev: rework dependencies

On Fri, Apr 17, 2020 at 07:14:53PM +0200, Daniel Vetter wrote:

On Fri, Apr 17, 2020 at 05:55:45PM +0200, Arnd Bergmann wrote:

quoted

I tried to fix up some dependencies after the sii8620 "imply EXTCON"
statementn broke, trying a few things but in the backing out a
change that would completely reverse the LEDS_CLASS selects into
a 'depends on'. 

However, what I got now are multiple changes that remove gratious
"selects" that lead to circular dependencies for sii8620 and others:

- Anything doing "select FB" is now gone, or becomes "depends on FB",

- DDC support depends on I2C instead of selecting it

- backlight class device support is never selected by framebuffer
  drivers but has proper dependencies

I have done thousands of randconfig build tests on this, but no
runtime tests.

Some of the 'depends on FOO || !FOO' statements could be simplified
into a new 'uses FOO' syntax based on a patch from Saeed Mahameed,
but I would for the moment treat that as a cleanup that can be done
later.

If we can agree on these changes, maybe someone can merge them
through the drm-misc tree.

Please review

Biggest concern I have is that usability of make menuconfig is horrible,
and it's very hard to find options that are hidden by depends on. You can
use the search interface, if you happen to know the option.

Once you've surmounted that bar, the next one is trying to find what
exactly you need to enable. Which again means endless of recursive
screaming at Kconfig files, since make menuconfig doesn't help you at all.

+1 on this. But this is a general kconfig problem, and not unique to
DRM, I've done this screaming for many different things now.. eg to
turn on every single RDMA driver.

I hackily delt with it by creating this rather insane script based on
the python kconfiglib to try and sort things out mostly automatically:

https://github.com/jgunthorpe/Kernel-Maintainer-Tools/blob/master/gj_tools/cmd_kconfig.py

It would be great if menuconfig had a key to say 'hey, really, turn
this on and everything it depends on, recursively'

Jason