Hi Arnd.
On Fri, Apr 17, 2020 at 05:55:51PM +0200, Arnd Bergmann wrote:
> CONFIG_DRM_KMS_FB_HELPER selects CONFIG_FB, which is something it
> really should not, to avoid circular dependencies and accidentally
> including potentially dangerous user interfaces in the kernel,
> so change this into a 'depends on' check.
>
> Two device drivers currently select CONFIG_DRM_KMS_FB_HELPER, but
> as far as I can tell, they do not really need to any more, so those
> selects can be removed.
>
> This leaves DRM_FBDEV_EMULATION as the only thing that rightfully
> selects CONFIG_DRM_KMS_FB_HELPER, and this now has to depend on
> CONFIG_FB and its dependencies.
>
> Signed-off-by: Arnd Bergmann <a...@arndb.de>
> ---
> drivers/gpu/drm/Kconfig | 5 +++--
> drivers/gpu/drm/mxsfb/Kconfig | 1 -
> drivers/gpu/drm/zte/Kconfig | 1 -
> 3 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 43594978958e..7c3109133685 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -80,7 +80,7 @@ config DRM_KMS_HELPER
> config DRM_KMS_FB_HELPER
> bool
> depends on DRM_KMS_HELPER
> - select FB
> + depends on FB
> select FRAMEBUFFER_CONSOLE if !EXPERT
> select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
> select FB_SYS_FOPS
> @@ -111,7 +111,8 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
>
> config DRM_FBDEV_EMULATION
> bool "Enable legacy fbdev support for your modesetting driver"
> - depends on DRM
> + depends on DRM && FB
> + depends on FB=y || DRM=m
> select DRM_KMS_HELPER
> select DRM_KMS_FB_HELPER
> default y
This statement:
depends on DRM && FB
tell us that both symbols must be either y or m. Any combination of y
and m will do the trick
Then we have this statement:
depends on FB=y || DRM=m
It tells us that either FB equals y or DRM equals m.
So we have following table
FB DRM Result
n n n
n y n
n m n
y n n
y y y
y m y
m n n
m y N
m m y
So what this try to say is that we cannot have FB a module while DRM is
built-in (marked N in the above).
Could you explain in the changelog why this combination is not good.
(Or tell me if my analysis was flawed).
With this fixed (assuming I am right):
Reviewed-by: Sam Ravnborg <s...@ravnborg.org>
Sam
> diff --git a/drivers/gpu/drm/mxsfb/Kconfig b/drivers/gpu/drm/mxsfb/Kconfig
> index 0dca8f27169e..33916b7b2c50 100644
> --- a/drivers/gpu/drm/mxsfb/Kconfig
> +++ b/drivers/gpu/drm/mxsfb/Kconfig
> @@ -10,7 +10,6 @@ config DRM_MXSFB
> depends on COMMON_CLK
> select DRM_MXS
> select DRM_KMS_HELPER
> - select DRM_KMS_FB_HELPER
> select DRM_KMS_CMA_HELPER
> select DRM_PANEL
> help
> diff --git a/drivers/gpu/drm/zte/Kconfig b/drivers/gpu/drm/zte/Kconfig
> index 90ebaedc11fd..aa8594190b50 100644
> --- a/drivers/gpu/drm/zte/Kconfig
> +++ b/drivers/gpu/drm/zte/Kconfig
> @@ -3,7 +3,6 @@ config DRM_ZTE
> tristate "DRM Support for ZTE SoCs"
> depends on DRM && ARCH_ZX
> select DRM_KMS_CMA_HELPER
> - select DRM_KMS_FB_HELPER
> select DRM_KMS_HELPER
> select SND_SOC_HDMI_CODEC if SND_SOC
> select VIDEOMODE_HELPERS
> --
> 2.26.0
>
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