Re: [PATCH] drm: fix up fbdev Kconfig defaults

Hi Thomas,

On Tue, Sep 12, 2023 at 10:38 AM Thomas Zimmermann [off-list ref] wrote:

Am 12.09.23 um 10:18 schrieb Geert Uytterhoeven:

quoted

On Tue, Sep 12, 2023 at 10:11 AM Thomas Zimmermann [off-list ref] wrote:

quoted

Am 12.09.23 um 09:14 schrieb Geert Uytterhoeven:
[...]

quoted

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.

Would it make sense to make FRAMEBUFFER_CONSOLE an independent option
and have FBDEV_EMULATION depend on it? Something like this:

FRAMEBUFFER_CONSOLE
         depends on DRM || FB
         select FB_CORE

FBDEV_EMULATION
         depends on DRM
         depends on FRAMEBUFFER_CONSOLE
         default y

Oops, now you can no longer have FBDEV_EMULATION without
FRAMEBUFFER_CONSOLE, which is useful to be able to enable
FB_DEVICE...

And if it depends on FB_CORE instead of FRAMEBUFFER_CONSOLE? I'm aware
that this would require more Kconfig changes than outlined here.

quoted

And what's the point (if DRM is enabled) of having FB_CORE with
FBDEV_EMULATION disabled?

quoted

So if any graphics subsystems are enabled, FRAMEBUFFER_CONSOLE is
select-able. But for DRM, FBDEV_EMULATION disables the console. That

Huh?

/me looks at his morning coffee, and confirms the cup is empty...

Decaf maybe?

But there's really no need to get snarky. My though is that

Sorry, I was surprised by "FBDEV_EMULATION disables the console",
which is not what the Kconfig snippet you suggested does?

FRAMEBUFFER_CONSOLE configures an end-user feature. The user sits there
an thinks "I want a console". FBDEV_EMULATION controls a driver
functionality. It's not useful by itself, but enables the enduser
feature. The features would be FRAMEBUFFER_CONSOLE and FRAMEBUFFER_DEVICE.

The latter is currently called FB_DEVICE.

If you want to have this controlled by user-visible features, then
either FRAMEBUFFER_CONSOLE and FRAMEBUFFER_DEVICE should
"select FBDEV_EMULATION if DRM", right?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds