From the comments in crosreview.com/1135724 (pasted here, where they belong):

---

Aleksander Miera writes:

> Just to avoid any misunderstandings:
> from what I can see the removal of every dependency that's pulled in by DRM_KMS_FB_HELPER from 
> EVDI's Kconfig is going to be a satisfactory solution in terms of "normalizing the configs", 
> but according to the bug report - you would like us to remove the FB's dependency completely 
> and rely on DRM_KMS_HELPER only? Is that right, or are we missing some important point here?

I'll paste the same thing as in the CL, yes let's have the discussion here:

We don't use FB at all in Chrome OS; we have removed it completely, as well as all the helpers. We only go through DRM for all display stuff.

And as such, we don't need (or want) DRM_KMS_FB_HELPER et al., for both resource consumption and security reasons.

As for DRM, this is an excerpt from its Kconfig:
menuconfig DRM

        tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI support)"
        depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
        select DRM_PANEL_ORIENTATION_QUIRKS
        select HDMI
        select FB_CMDLINE
        select I2C
        select I2C_ALGOBIT
        select DMA_SHARED_BUFFER
        select SYNC_FILE
        help

Please note FB_CMDLINE.

As for FBDEV's Kconfig

menuconfig FB
        tristate "Support for frame buffer devices"
        select FB_CMDLINE
        select FB_NOTIFY
(...)

config FB_CMDLINE
        bool

config FB_NOTIFY
        bool


Now the question is, if we should eliminate dependency on DRM_KMS_FB_HELPER et al. only, or on complete FB (EVDI should build w/o CONFIG_FB set in base.config), which seems to be DRM's dependency, unless I am horribly misinterpreting it.

Could you please be a bit more verbose on that topic?

DRM doesn't depend on CONFIG_FB, nor does it depend on DRM_KMS_FB_HELPER. In Chrome OS, we enable neither, and we want to keep it that way.

So, this bug is about making evdi work without these (either by removing FB support or by  making it optional one way or another).

This bug has an owner, thus, it's been triaged. Changing status to "assigned".

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/a917d8f356cb0af3d1d34099bb29af8a5fa70607

commit a917d8f356cb0af3d1d34099bb29af8a5fa70607
Author: Aleksander Miera <aleksander.miera@displaylink.com>
Date: Fri Aug 17 23:14:22 2018

drm/evdi: remove dependency on CONFIG_FB

BUG=chromium:863173
TEST=tested on board Eve

Change-Id: I4b69c0ba6912190418aa401e65fc33ac88f889ab
Signed-off-by: Aleksander Miera <aleksander.miera@displaylink.com>
Reviewed-on: https://chromium-review.googlesource.com/1154976
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>

[modify] https://crrev.com/a917d8f356cb0af3d1d34099bb29af8a5fa70607/drivers/gpu/drm/evdi/evdi_fb.c
[modify] https://crrev.com/a917d8f356cb0af3d1d34099bb29af8a5fa70607/drivers/gpu/drm/evdi/evdi_main.c
[modify] https://crrev.com/a917d8f356cb0af3d1d34099bb29af8a5fa70607/drivers/gpu/drm/evdi/evdi_drv.c
[modify] https://crrev.com/a917d8f356cb0af3d1d34099bb29af8a5fa70607/drivers/gpu/drm/evdi/evdi_drv.h
[modify] https://crrev.com/a917d8f356cb0af3d1d34099bb29af8a5fa70607/drivers/gpu/drm/evdi/Kconfig

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/6ddd150a4b22dbe572d4c3233fa0f0cc9f6db149

commit 6ddd150a4b22dbe572d4c3233fa0f0cc9f6db149
Author: Douglas Anderson <dianders@chromium.org>
Date: Wed Aug 22 02:27:52 2018

CHROMIUM: config: normalize (FRAMEBUFFER + HOTPLUG_SMT)

Just run './chromeos/scripts/kernelconfig olddefconfig'

Much of this is essentially a revert of a previous normalization in
CL:1135724.  See chromium:863173 for details.  The last bit
(CONFIG_HOTPLUG_SMT) is due to stable merge from commit c5ac43ee8c77
("cpu/hotplug: Provide knobs to control SMT")

BUG=chromium:863173
TEST=None

Change-Id: Icba563a3a4e040828bd438df8cb6e3deae41daf5
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1182405
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>

[modify] https://crrev.com/6ddd150a4b22dbe572d4c3233fa0f0cc9f6db149/chromeos/config/x86_64/common.config
[modify] https://crrev.com/6ddd150a4b22dbe572d4c3233fa0f0cc9f6db149/chromeos/config/i386/common.config
[modify] https://crrev.com/6ddd150a4b22dbe572d4c3233fa0f0cc9f6db149/chromeos/config/base.config

@displaylink, it looks like older kernels are also affected. Can you prepare changes for these kernels?

Should this be also backported to 3.8?
The reason I'm asking this is the the fact, that in 3.8 DRM_KMS_HELPER (which I do not think we can easily get rid of) selects FB anyway:

config DRM_KMS_HELPER
        tristate
        depends on DRM
        select FB
        select FRAMEBUFFER_CONSOLE if !EXPERT
        select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
        help
          FB and CRTC helpers for KMS drivers.

Yes it should go to all our other kernels, not just 4.14. That's 3.8, 3.10 (this one maybe doesn't have evdi), 3.14, 3.18 and 4.4.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/a55bd208fd57ba1a0579c91433c43888dc76864e

commit a55bd208fd57ba1a0579c91433c43888dc76864e
Author: Aleksander Miera <aleksander.miera@displaylink.com>
Date: Wed Jan 16 13:25:53 2019

drm/evdi: remove direct dependency on FB_*-related kernel options

BUG=chromium:863173
TEST=none

Change-Id: I25e91b200e1059800f9bfa1b68a2eaa2dd48eae1
Signed-off-by: Aleksander Miera <aleksander.miera@displaylink.com>
Reviewed-on: https://chromium-review.googlesource.com/1411573
Commit-Ready: Dawid Kurek <dawid.kurek@displaylink.com>
Tested-by: Dawid Kurek <dawid.kurek@displaylink.com>
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>

[modify] https://crrev.com/a55bd208fd57ba1a0579c91433c43888dc76864e/drivers/gpu/drm/evdi/evdi_fb.c
[modify] https://crrev.com/a55bd208fd57ba1a0579c91433c43888dc76864e/drivers/gpu/drm/evdi/evdi_main.c
[modify] https://crrev.com/a55bd208fd57ba1a0579c91433c43888dc76864e/drivers/gpu/drm/evdi/evdi_drv.h
[modify] https://crrev.com/a55bd208fd57ba1a0579c91433c43888dc76864e/drivers/gpu/drm/evdi/Kconfig

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/f966bc7c46bc2e2e34ffc158263b5ec84823bd5e

commit f966bc7c46bc2e2e34ffc158263b5ec84823bd5e
Author: Aleksander Miera <aleksander.miera@displaylink.com>
Date: Wed Jan 16 13:25:43 2019

drm/evdi: remove dependency on CONFIG_FB

BUG=chromium:863173
TEST=none

Change-Id: Ie981caf18fa07446fc22846e741e79a3ac28801e
Signed-off-by: Aleksander Miera <aleksander.miera@displaylink.com>
Reviewed-on: https://chromium-review.googlesource.com/1411577
Commit-Ready: Dawid Kurek <dawid.kurek@displaylink.com>
Tested-by: Dawid Kurek <dawid.kurek@displaylink.com>
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>

[modify] https://crrev.com/f966bc7c46bc2e2e34ffc158263b5ec84823bd5e/drivers/gpu/drm/evdi/evdi_fb.c
[modify] https://crrev.com/f966bc7c46bc2e2e34ffc158263b5ec84823bd5e/drivers/gpu/drm/evdi/evdi_main.c
[modify] https://crrev.com/f966bc7c46bc2e2e34ffc158263b5ec84823bd5e/drivers/gpu/drm/evdi/evdi_drv.h
[modify] https://crrev.com/f966bc7c46bc2e2e34ffc158263b5ec84823bd5e/drivers/gpu/drm/evdi/Kconfig

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/2050d95498dbddb609c60f00788ac59800387d22

commit 2050d95498dbddb609c60f00788ac59800387d22
Author: Aleksander Miera <aleksander.miera@displaylink.com>
Date: Wed Jan 16 13:25:56 2019

drm/evdi: remove dependency on CONFIG_FB

BUG=chromium:863173
TEST=manual on board lulu

Change-Id: I717142b3a9236054cc65ed03721a621d35f445f5
Signed-off-by: Aleksander Miera <aleksander.miera@displaylink.com>
Reviewed-on: https://chromium-review.googlesource.com/1411582
Commit-Ready: Dawid Kurek <dawid.kurek@displaylink.com>
Tested-by: Dawid Kurek <dawid.kurek@displaylink.com>
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>

[modify] https://crrev.com/2050d95498dbddb609c60f00788ac59800387d22/drivers/gpu/drm/evdi/evdi_fb.c
[modify] https://crrev.com/2050d95498dbddb609c60f00788ac59800387d22/drivers/gpu/drm/evdi/evdi_main.c
[modify] https://crrev.com/2050d95498dbddb609c60f00788ac59800387d22/drivers/gpu/drm/evdi/evdi_drv.h
[modify] https://crrev.com/2050d95498dbddb609c60f00788ac59800387d22/drivers/gpu/drm/evdi/Kconfig

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/6a3b17f1172ad27e063f7c44524f52f3fb45d6b5

commit 6a3b17f1172ad27e063f7c44524f52f3fb45d6b5
Author: Aleksander Miera <aleksander.miera@displaylink.com>
Date: Wed Jan 16 13:26:02 2019

drm/evdi: remove dependency on CONFIG_FB

BUG=chromium:863173
TEST=manual on board chell

Change-Id: Ib190b74495046d48cad6d9fe5283a63b40ed6a7e
Signed-off-by: Aleksander Miera <aleksander.miera@displaylink.com>
Reviewed-on: https://chromium-review.googlesource.com/1411590
Commit-Ready: Dawid Kurek <dawid.kurek@displaylink.com>
Tested-by: Dawid Kurek <dawid.kurek@displaylink.com>
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>

[modify] https://crrev.com/6a3b17f1172ad27e063f7c44524f52f3fb45d6b5/drivers/gpu/drm/evdi/evdi_fb.c
[modify] https://crrev.com/6a3b17f1172ad27e063f7c44524f52f3fb45d6b5/drivers/gpu/drm/evdi/evdi_main.c
[modify] https://crrev.com/6a3b17f1172ad27e063f7c44524f52f3fb45d6b5/drivers/gpu/drm/evdi/evdi_drv.h
[modify] https://crrev.com/6a3b17f1172ad27e063f7c44524f52f3fb45d6b5/drivers/gpu/drm/evdi/Kconfig