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

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

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.

That's pretty much why we've never pushed this in, and instead done the
selects. I'm vary applying all this, since after after there'll be all the
screaming again and we have to back it out.

I think to embrace this without regrets what we need is:
- some way to list the hidden options
- some way to browse the depedencies of those hidden options

menuconfig cant do that, gconfig I cant build here (it's some old gtk2
thing, where do you even get the deps for that). xconfig also cant do
this easily, dependencies aren't linked.

So yeah not sure this is a good idea at all, until at least menuconfig can
cope.
-Daniel

       Arnd

Arnd Bergmann (8):
  fbdev: w100fb: clean up mach-pxa compile-time dependency
  fbdev/ARM: pxa: avoid selecting CONFIG_FB
  fbdev: rework FB_DDC dependencies
  drm/rcar: stop using 'imply' for dependencies
  drm/vmwgfx: make framebuffer support optional
  drm: decouple from CONFIG_FB
  fbdev: rework backlight dependencies
  drm/bridge/sii8620: fix extcon dependency

 arch/arm/configs/pxa_defconfig      |  3 ++
 arch/arm/mach-pxa/Kconfig           |  7 ---
 arch/arm/mach-pxa/eseries.c         | 14 +----
 arch/arm/mach-pxa/saar.c            |  2 +-
 arch/arm/mach-pxa/tavorevb.c        |  2 +-
 drivers/auxdisplay/Kconfig          |  1 +
 drivers/gpu/drm/Kconfig             |  5 +-
 drivers/gpu/drm/bridge/Kconfig      |  2 +-
 drivers/gpu/drm/mxsfb/Kconfig       |  1 -
 drivers/gpu/drm/rcar-du/Kconfig     | 23 +++++---
 drivers/gpu/drm/vmwgfx/Kconfig      | 17 +++---
 drivers/gpu/drm/vmwgfx/Makefile     |  4 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 35 +++++++-----
 drivers/gpu/drm/zte/Kconfig         |  1 -
 drivers/macintosh/Kconfig           |  1 +
 drivers/staging/fbtft/Kconfig       |  1 +
 drivers/staging/olpc_dcon/Kconfig   |  2 +-
 drivers/video/fbdev/Kconfig         | 31 ++++++++---
 drivers/video/fbdev/w100fb.c        | 84 +++++------------------------
 include/video/w100fb.h              |  6 +--
 20 files changed, 101 insertions(+), 141 deletions(-)

-- 
2.26.0

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Andrzej Hajda <redacted>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Saeed Mahameed <redacted>
Cc: <masahiroy@kernel.org>
Cc: <Laurent.pinchart@ideasonboard.com>
Cc: <redacted>,
Cc: "dri-devel@lists.freedesktop.org" <redacted>,
Cc: <kieran.bingham+renesas@ideasonboard.com>,
Cc: <redacted>
Cc: daniel@zonque.org
Cc: haojian.zhuang@gmail.com
Cc: robert.jarzmik@free.fr
Cc: daniel@ffwll.ch
Cc: marex@denx.de
Cc: stefan@agner.ch
Cc: linux-graphics-maintainer@vmware.com
Cc: thellstrom@vmware.com
Cc: jfrederich@gmail.com
Cc: dsd@laptop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: geert@linux-m68k.org

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch