diff mbox series

[SUBMITTED,20210721] fbdev: simplefb: fix Kconfig dependencies

Message ID 20210928145243.1098064-1-arnd@kernel.org
State New
Headers show
Series [SUBMITTED,20210721] fbdev: simplefb: fix Kconfig dependencies | expand

Commit Message

Arnd Bergmann Sept. 28, 2021, 2:52 p.m. UTC
From: Arnd Bergmann <arnd@arndb.de>


Configurations with both CONFIG_FB_SIMPLE=y and CONFIG_DRM_SIMPLEDRM=m
are allowed by Kconfig because the 'depends on !DRM_SIMPLEDRM' dependency
does not disallow FB_SIMPLE as long as SIMPLEDRM is not built-in. This
can however result in a build failure when cfb_fillrect() etc are then
also in loadable modules:

x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x1f8): undefined reference to `cfb_fillrect'
x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x200): undefined reference to `cfb_copyarea'
x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x208): undefined reference to `cfb_imageblit'

To work around this, change FB_SIMPLE to be a 'tristate' symbol,
which still allows both to be =m together, but not one of them to
be =y if the other one is =m. If a distro kernel picks this
configuration, it can be determined by local policy which of
the two modules gets loaded. The 'of_chosen' export is needed
as this is the first loadable module referencing it.

Alternatively, the Kconfig dependency could be changed to
'depends on DRM_SIMPLEDRM=n', which would forbid the configuration
with both drivers.

Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
Acked-by: Rob Herring <robh@kernel.org> # for drivers/of/

Link: https://lore.kernel.org/all/20210721151839.2484245-1-arnd@kernel.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 drivers/of/base.c           | 1 +
 drivers/video/fbdev/Kconfig | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

-- 
2.29.2

Comments

Thomas Zimmermann Sept. 29, 2021, 8:14 a.m. UTC | #1
Hi

Am 28.09.21 um 16:52 schrieb Arnd Bergmann:
> From: Arnd Bergmann <arnd@arndb.de>

> 

> Configurations with both CONFIG_FB_SIMPLE=y and CONFIG_DRM_SIMPLEDRM=m

> are allowed by Kconfig because the 'depends on !DRM_SIMPLEDRM' dependency

> does not disallow FB_SIMPLE as long as SIMPLEDRM is not built-in. This

> can however result in a build failure when cfb_fillrect() etc are then

> also in loadable modules:

> 

> x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x1f8): undefined reference to `cfb_fillrect'

> x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x200): undefined reference to `cfb_copyarea'

> x86_64-linux-ld: drivers/video/fbdev/simplefb.o:(.rodata+0x208): undefined reference to `cfb_imageblit'

> 

> To work around this, change FB_SIMPLE to be a 'tristate' symbol,

> which still allows both to be =m together, but not one of them to

> be =y if the other one is =m. If a distro kernel picks this

> configuration, it can be determined by local policy which of

> the two modules gets loaded. The 'of_chosen' export is needed

> as this is the first loadable module referencing it.

> 

> Alternatively, the Kconfig dependency could be changed to

> 'depends on DRM_SIMPLEDRM=n', which would forbid the configuration

> with both drivers.

> 

> Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")

> Acked-by: Rob Herring <robh@kernel.org> # for drivers/of/

> Link: https://lore.kernel.org/all/20210721151839.2484245-1-arnd@kernel.org/

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


I've added a few CC tags and merged the patch into drm-misc-fixes. 
Thanks for your patience and perseverance.

Best regards
Thomas

> ---

>   drivers/of/base.c           | 1 +

>   drivers/video/fbdev/Kconfig | 5 +++--

>   2 files changed, 4 insertions(+), 2 deletions(-)

> 

> diff --git a/drivers/of/base.c b/drivers/of/base.c

> index f720c0d246f2..0ac17256258d 100644

> --- a/drivers/of/base.c

> +++ b/drivers/of/base.c

> @@ -36,6 +36,7 @@ LIST_HEAD(aliases_lookup);

>   struct device_node *of_root;

>   EXPORT_SYMBOL(of_root);

>   struct device_node *of_chosen;

> +EXPORT_SYMBOL(of_chosen);

>   struct device_node *of_aliases;

>   struct device_node *of_stdout;

>   static const char *of_stdout_options;

> diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig

> index b26b79dfcac9..6ed5e608dd04 100644

> --- a/drivers/video/fbdev/Kconfig

> +++ b/drivers/video/fbdev/Kconfig

> @@ -2193,8 +2193,9 @@ config FB_HYPERV

>   	  This framebuffer driver supports Microsoft Hyper-V Synthetic Video.

>   

>   config FB_SIMPLE

> -	bool "Simple framebuffer support"

> -	depends on (FB = y) && !DRM_SIMPLEDRM

> +	tristate "Simple framebuffer support"

> +	depends on FB

> +	depends on !DRM_SIMPLEDRM

>   	select FB_CFB_FILLRECT

>   	select FB_CFB_COPYAREA

>   	select FB_CFB_IMAGEBLIT

> 


-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
diff mbox series

Patch

diff --git a/drivers/of/base.c b/drivers/of/base.c
index f720c0d246f2..0ac17256258d 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -36,6 +36,7 @@  LIST_HEAD(aliases_lookup);
 struct device_node *of_root;
 EXPORT_SYMBOL(of_root);
 struct device_node *of_chosen;
+EXPORT_SYMBOL(of_chosen);
 struct device_node *of_aliases;
 struct device_node *of_stdout;
 static const char *of_stdout_options;
diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index b26b79dfcac9..6ed5e608dd04 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -2193,8 +2193,9 @@  config FB_HYPERV
 	  This framebuffer driver supports Microsoft Hyper-V Synthetic Video.
 
 config FB_SIMPLE
-	bool "Simple framebuffer support"
-	depends on (FB = y) && !DRM_SIMPLEDRM
+	tristate "Simple framebuffer support"
+	depends on FB
+	depends on !DRM_SIMPLEDRM
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT