diff mbox series

[v5,3/4] fbdev: Split frame buffer support in FB and FB_CORE symbols

Message ID 20230714171642.91185-4-javierm@redhat.com
State New
Headers
Series Allow disabling all native fbdev drivers and only keeping DRM emulation |

Commit Message

Javier Martinez Canillas July 14, 2023, 5:16 p.m. UTC 
  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.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---

Changes in v5:
- Fix ifdef guard check in drivers/video/backlight/backlight.c (Arnd Bergmann).

Changes in v4:
- Fix menuconfig hierarchy that was broken in v3 (Arnd Bergmann).

Changes in v3:
- Really make a hidden symbol by removing the prompt (Arnd Bergmann).
- Change FB_CORE to config instead of menuconfig (Arnd Bergmann).
- Keep "depends on FB" for FIRMWARE_EDID (Arnd Bergmann).
- Compile out fb_backlight.o and fbmon.o that are only needed for FB
  (Arnd Bergmann).
- Make FB_DEVICE to depend on FB_CORE instead of selecting it.

Changes in v2:
- Keep "depends on FB" for FB_DDC, FB_HECUBA, FB_SVGALIB, FB_MACMODES,
  FB_BACKLIGHT, FB_MODE_HELPERS and FB_TILEBLITTING (Arnd Bergmann).
- Don't change the fb.o object name (Arnd Bergmann).
- Make FB_CORE a non-visible Kconfig symbol instead (Thomas Zimmermann).

 arch/x86/Makefile                   |  2 +-
 arch/x86/video/Makefile             |  2 +-
 drivers/video/backlight/backlight.c |  6 +++---
 drivers/video/console/Kconfig       |  2 +-
 drivers/video/fbdev/Kconfig         | 10 ++++++++--
 drivers/video/fbdev/core/Kconfig    | 30 ++++++++++++++++-------------
 drivers/video/fbdev/core/Makefile   |  8 ++++----
 7 files changed, 35 insertions(+), 25 deletions(-)

Comments

Arnd Bergmann July 18, 2023, 7:27 p.m. UTC | #1 
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:

> diff --git a/drivers/video/fbdev/core/Makefile 
> b/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-$(CONFIG_FB_CORE)             += fb.o
> +fb-y                              := fb_info.o \
> +                                     fbmem.o fbcmap.o \
>                                       modedb.o fbcvt.o fb_cmdline.o 
> fb_io_fops.o
> +fb-$(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
Javier Martinez Canillas July 19, 2023, 7:57 a.m. UTC | #2 
"Arnd Bergmann" <arnd@arndb.de> writes:

> 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:
>

Thanks for testing!

>> diff --git a/drivers/video/fbdev/core/Makefile 
>> b/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-$(CONFIG_FB_CORE)             += fb.o
>> +fb-y                              := fb_info.o \
>> +                                     fbmem.o fbcmap.o \
>>                                       modedb.o fbcvt.o fb_cmdline.o 
>> fb_io_fops.o
>> +fb-$(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!
>

Right, sorry for missing that combination.

>
> 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 \
>

Perfect, I'll squash your fix in v6. Thanks!
diff mbox series

Patch

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index b39975977c03..89a02e69be5f 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -259,7 +259,7 @@  drivers-$(CONFIG_PCI)            += arch/x86/pci/
 # suspend and hibernation support
 drivers-$(CONFIG_PM) += arch/x86/power/
 
-drivers-$(CONFIG_FB) += arch/x86/video/
+drivers-$(CONFIG_FB_CORE) += arch/x86/video/
 
 ####
 # boot loader support. Several targets are kept for legacy purposes
diff --git a/arch/x86/video/Makefile b/arch/x86/video/Makefile
index 11640c116115..5ebe48752ffc 100644
--- a/arch/x86/video/Makefile
+++ b/arch/x86/video/Makefile
@@ -1,2 +1,2 @@ 
 # SPDX-License-Identifier: GPL-2.0-only
-obj-$(CONFIG_FB)               += fbdev.o
+obj-$(CONFIG_FB_CORE)		+= fbdev.o
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 9a885d398c22..86e1cdc8e369 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -79,8 +79,8 @@  static const char *const backlight_scale_types[] = {
 	[BACKLIGHT_SCALE_NON_LINEAR]	= "non-linear",
 };
 
-#if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
-			   defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
+#if defined(CONFIG_FB_CORE) || (defined(CONFIG_FB_CORE_MODULE) && \
+				defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
 /*
  * fb_notifier_callback
  *
@@ -155,7 +155,7 @@  static inline int backlight_register_fb(struct backlight_device *bd)
 static inline void backlight_unregister_fb(struct backlight_device *bd)
 {
 }
-#endif /* CONFIG_FB */
+#endif /* CONFIG_FB_CORE */
 
 static void backlight_generate_event(struct backlight_device *bd,
 				     enum backlight_update_reason reason)
diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
index a2a88d42edf0..1b5a319971ed 100644
--- a/drivers/video/console/Kconfig
+++ b/drivers/video/console/Kconfig
@@ -72,7 +72,7 @@  config DUMMY_CONSOLE_ROWS
 
 config FRAMEBUFFER_CONSOLE
 	bool "Framebuffer Console support"
-	depends on FB && !UML
+	depends on FB_CORE && !UML
 	select VT_HW_CONSOLE_BINDING
 	select CRC32
 	select FONT_SUPPORT
diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index ec4068abeb8e..7e65a648f71a 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -4,9 +4,9 @@ 
 #
 
 menuconfig FB
-	tristate "Support for frame buffer devices"
+	tristate "Support for frame buffer device drivers"
+	select FB_CORE
 	select FB_NOTIFY
-	select VIDEO_CMDLINE
 	help
 	  The frame buffer device provides an abstraction for the graphics
 	  hardware. It represents the frame buffer of some video hardware and
@@ -30,6 +30,12 @@  menuconfig FB
 	  <http://www.munted.org.uk/programming/Framebuffer-HOWTO-1.3.html> for more
 	  information.
 
+	  This enables support for native frame buffer device (fbdev) drivers.
+
+	  The DRM subsystem provides support for emulated frame buffer devices
+	  on top of KMS drivers, but this option allows legacy fbdev drivers to
+	  be enabled as well.
+
 	  Say Y here and to the driver for your graphics board below if you
 	  are compiling a kernel for a non-x86 architecture.
 
diff --git a/drivers/video/fbdev/core/Kconfig b/drivers/video/fbdev/core/Kconfig
index 8e308d12c57b..15ce529d579a 100644
--- a/drivers/video/fbdev/core/Kconfig
+++ b/drivers/video/fbdev/core/Kconfig
@@ -3,6 +3,10 @@ 
 # fbdev core configuration
 #
 
+config FB_CORE
+	select VIDEO_CMDLINE
+	tristate
+
 config FB_NOTIFY
 	bool
 
@@ -23,7 +27,7 @@  config FIRMWARE_EDID
 
 config FB_DEVICE
 	bool "Provide legacy /dev/fb* device"
-	depends on FB
+	depends on FB_CORE
 	default y
 	help
 	  Say Y here if you want the legacy /dev/fb* device file and
@@ -39,7 +43,7 @@  config FB_DDC
 
 config FB_CFB_FILLRECT
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the cfb_fillrect function for generic software rectangle
 	  filling. This is used by drivers that don't provide their own
@@ -47,7 +51,7 @@  config FB_CFB_FILLRECT
 
 config FB_CFB_COPYAREA
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the cfb_copyarea function for generic software area copying.
 	  This is used by drivers that don't provide their own (accelerated)
@@ -55,7 +59,7 @@  config FB_CFB_COPYAREA
 
 config FB_CFB_IMAGEBLIT
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the cfb_imageblit function for generic software image
 	  blitting. This is used by drivers that don't provide their own
@@ -63,7 +67,7 @@  config FB_CFB_IMAGEBLIT
 
 config FB_CFB_REV_PIXELS_IN_BYTE
 	bool
-	depends on FB
+	depends on FB_CORE
 	help
 	  Allow generic frame-buffer functions to work on displays with 1, 2
 	  and 4 bits per pixel depths which has opposite order of pixels in
@@ -71,7 +75,7 @@  config FB_CFB_REV_PIXELS_IN_BYTE
 
 config FB_SYS_FILLRECT
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the sys_fillrect function for generic software rectangle
 	  filling. This is used by drivers that don't provide their own
@@ -79,7 +83,7 @@  config FB_SYS_FILLRECT
 
 config FB_SYS_COPYAREA
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the sys_copyarea function for generic software area copying.
 	  This is used by drivers that don't provide their own (accelerated)
@@ -87,7 +91,7 @@  config FB_SYS_COPYAREA
 
 config FB_SYS_IMAGEBLIT
 	tristate
-	depends on FB
+	depends on FB_CORE
 	help
 	  Include the sys_imageblit function for generic software image
 	  blitting. This is used by drivers that don't provide their own
@@ -126,22 +130,22 @@  endchoice
 
 config FB_SYS_FOPS
 	tristate
-	depends on FB
+	depends on FB_CORE
 
 config FB_DEFERRED_IO
 	bool
-	depends on FB
+	depends on FB_CORE
 
 config FB_IO_HELPERS
 	bool
-	depends on FB
+	depends on FB_CORE
 	select FB_CFB_COPYAREA
 	select FB_CFB_FILLRECT
 	select FB_CFB_IMAGEBLIT
 
 config FB_SYS_HELPERS
 	bool
-	depends on FB
+	depends on FB_CORE
 	select FB_SYS_COPYAREA
 	select FB_SYS_FILLRECT
 	select FB_SYS_FOPS
@@ -149,7 +153,7 @@  config FB_SYS_HELPERS
 
 config FB_SYS_HELPERS_DEFERRED
 	bool
-	depends on FB
+	depends on FB_CORE
 	select FB_DEFERRED_IO
 	select FB_SYS_HELPERS
 
diff --git a/drivers/video/fbdev/core/Makefile b/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-$(CONFIG_FB_CORE)             += fb.o
+fb-y                              := fb_info.o \
+                                     fbmem.o fbcmap.o \
                                      modedb.o fbcvt.o fb_cmdline.o fb_io_fops.o
+fb-$(CONFIG_FB)                   += fb_backlight.o fbmon.o
 fb-$(CONFIG_FB_DEFERRED_IO)       += fb_defio.o
 fb-$(CONFIG_FB_DEVICE)            += fb_chrdev.o \
                                      fb_procfs.o \