Re: [PATCH v5 3/4] fbdev: Split frame buffer support in FB and FB_CORE symbols
From: "Arnd Bergmann" <arnd@arndb.de>
Date: 2023-07-18 19:28:09
Also in:
dri-devel, lkml
Subsystem:
framebuffer core, framebuffer layer, the rest · Maintainers:
Simona Vetter, Helge Deller, Linus Torvalds
On Fri, Jul 14, 2023, at 19:16, Javier Martinez Canillas wrote:
Currently the CONFIG_FB option has to be enabled even if no legacy fbdev drivers are needed (e.g: only to have support for framebuffer consoles). The DRM subsystem has a fbdev emulation layer, but depends on CONFIG_FB and so it can only be enabled if that dependency is enabled as well. That means fbdev drivers have to be explicitly disabled if users want to enable CONFIG_FB, only to use fbcon and/or the DRM fbdev emulation layer. This patch introduces a non-visible CONFIG_FB_CORE symbol that could be enabled just to have core support needed for CONFIG_DRM_FBDEV_EMULATION, allowing CONFIG_FB to be disabled (and automatically disabling all the fbdev drivers). Nothing from fb_backlight.o and fbmon.o is used by the DRM fbdev emulation layer so these two objects can be compiled out when CONFIG_FB is disabled.
I gave this a spin in my randconfig build setup and found one small mistake:
quoted hunk ↗ jump to hunk
diff --git a/drivers/video/fbdev/core/Makefileb/drivers/video/fbdev/core/Makefile index 9150bafd9e89..2cd213716c12 100644--- a/drivers/video/fbdev/core/Makefile +++ b/drivers/video/fbdev/core/Makefile@@ -1,10 +1,10 @@ # SPDX-License-Identifier: GPL-2.0 obj-$(CONFIG_FB_NOTIFY) += fb_notify.o -obj-$(CONFIG_FB) += fb.o -fb-y := fb_backlight.o \ - fb_info.o \ - fbmem.o fbmon.o fbcmap.o \ +obj-$(CONFIG_FB_CORE) += fb.o +fb-y := fb_info.o \ + fbmem.o fbcmap.o \ modedb.o fbcvt.o fb_cmdline.ofb_io_fops.o +fb-$(CONFIG_FB) += fb_backlight.o fbmon.o
With CONFIG_FB_CORE=y and CONFIG_FB=m, Kbuild does not include the fb_backlight.o and fbmon.o files in fb.ko because they are not set to =y, causing link failures for fbdev drivers later: ERROR: modpost: "of_get_fb_videomode" [drivers/video/fbdev/clps711x-fb.ko] undefined! ERROR: modpost: "fb_videomode_from_videomode" [drivers/video/fbdev/atmel_lcdfb.ko] undefined! ERROR: modpost: "of_get_fb_videomode" [drivers/video/fbdev/imxfb.ko] undefined! ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/udlfb.ko] undefined! ERROR: modpost: "fb_edid_to_monspecs" [drivers/video/fbdev/udlfb.ko] undefined! ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/smscufx.ko] undefined! ERROR: modpost: "fb_edid_to_monspecs" [drivers/video/fbdev/smscufx.ko] undefined! ERROR: modpost: "fb_destroy_modedb" [drivers/video/fbdev/uvesafb.ko] undefined! ERROR: modpost: "fb_validate_mode" [drivers/video/fbdev/uvesafb.ko] undefined! ERROR: modpost: "fb_get_mode" [drivers/video/fbdev/uvesafb.ko] undefined! Folding this fixup into the patch makes it work:
diff --git a/drivers/video/fbdev/core/Makefile b/drivers/video/fbdev/core/Makefile
index 2cd213716c12f..84ddc5d308b58 100644
--- a/drivers/video/fbdev/core/Makefile
+++ b/drivers/video/fbdev/core/Makefile@@ -4,7 +4,9 @@ obj-$(CONFIG_FB_CORE) += fb.o fb-y := fb_info.o \ fbmem.o fbcmap.o \ modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o -fb-$(CONFIG_FB) += fb_backlight.o fbmon.o +ifdef CONFIG_FB +fb-y += fb_backlight.o fbmon.o +endif fb-$(CONFIG_FB_DEFERRED_IO) += fb_defio.o fb-$(CONFIG_FB_DEVICE) += fb_chrdev.o \ fb_procfs.o \ Arnd