On Tue, Sep 12, 2023, at 09:14, Geert Uytterhoeven wrote:

On Mon, Sep 11, 2023 at 10:53 PM Arnd Bergmann [off-list ref] wrote:

quoted

--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig

@@ -135,7 +135,7 @@ config DRM_FBDEV_EMULATION
        bool "Enable legacy fbdev support for your modesetting driver"
        depends on DRM
        select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
-       default y
+       default FB

While this is true for existing configs, it is no longer true in general,
as DRM_FBDEV_EMULATION is no longer related to FB.

I think it still makes some sense though, as configs that have
both DRM and FB enabled almost certainly want this enabled.

quoted

diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index b575cf54174af..83c2d7329ca58 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig

@@ -74,6 +74,7 @@ config DUMMY_CONSOLE_ROWS
 config FRAMEBUFFER_CONSOLE
        bool "Framebuffer Console support"
        depends on FB_CORE && !UML
+       default DRM_FBDEV_EMULATION

Sounds good to me, although it looks a bit strange at first sight
(FRAMEBUFFER_CONSOLE defaults to n on a system with real fbdev, but
y on emulated fbdev?).
So this is the fix for commit a5ae331edb02b ("drm: Drop select
FRAMEBUFFER_CONSOLE for DRM_FBDEV_EMULATION").

Correct, this should restore the console on configs that
accidentally lost it. The real problem here is much older,
the assymetry between framebuffer-only configs (with console
default off) and DRM configs (with console selected
unconditionally) started back in 2009 with commit 6fcefd56f5060
("drm/kms: fix kms helper license + Kconfig").

I think that was a mistake, but there is little we can do
to fix that now without breaking users.

The only alternative I can think of would be to default-enable
or force-enable FRAMEBUFFER_CONSOLE for any config that includes
both VT_CONSOLE and FB_CORE. This would increase defconfig
builds for systems that currently only want CONFIG_FB for
either FB_DEVICE or LOGO but don't care about
FRAMEBUFFER_CONSOLE. I have no idea who uses such a config,
but I think Javier previously said this was an important
use case.

quoted

diff --git a/drivers/video/fbdev/core/Kconfig b/drivers/video/fbdev/core/Kconfig
index 114cb8aa6c8fd..804c2bec9b43c 100644
--- a/drivers/video/fbdev/core/Kconfig
+++ b/drivers/video/fbdev/core/Kconfig

@@ -28,7 +28,7 @@ config FIRMWARE_EDID
 config FB_DEVICE
        bool "Provide legacy /dev/fb* device"
        depends on FB_CORE
-       default y
+       default FB

Changing this means possibly causing regressions on systems running
an fbdev userspace.

How? FB_DEVICE is a new config that was just split out from
CONFIG_FB in 6.6-rc1, so nobody should have any defconfig
that disables CONFIG_FB but relies on the FB_DEVICE default yet.

    Arnd