From: Noralf Trønnes noralf@tronnes.org
[ Upstream commit 3389669ac5ea598562673c04971d7bb0fab0e9f1 ]
The mipi_dbi helper is missing a dependency on DRM_KMS_HELPER and putting that in revealed this problem:
drivers/video/fbdev/Kconfig:12:error: recursive dependency detected! drivers/video/fbdev/Kconfig:12: symbol FB is selected by DRM_KMS_FB_HELPER drivers/gpu/drm/Kconfig:75: symbol DRM_KMS_FB_HELPER depends on DRM_KMS_HELPER drivers/gpu/drm/Kconfig:69: symbol DRM_KMS_HELPER is selected by TINYDRM_MIPI_DBI drivers/gpu/drm/tinydrm/Kconfig:11: symbol TINYDRM_MIPI_DBI is selected by TINYDRM_HX8357D drivers/gpu/drm/tinydrm/Kconfig:15: symbol TINYDRM_HX8357D depends on BACKLIGHT_CLASS_DEVICE drivers/video/backlight/Kconfig:144: symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT drivers/video/fbdev/Kconfig:187: symbol FB_BACKLIGHT depends on FB
A symbol that selects DRM_KMS_HELPER can not depend on BACKLIGHT_CLASS_DEVICE. The reason for this is that DRM_KMS_FB_HELPER selects FB instead of depending on it.
The tinydrm drivers have somehow gotten away with depending on BACKLIGHT_CLASS_DEVICE because DRM_TINYDRM selects DRM_KMS_HELPER and the drivers depend on that symbol.
An audit shows that all DRM drivers that select DRM_KMS_HELPER and use BACKLIGHT_CLASS_DEVICE, selects it: DRM_TILCDC, DRM_GMA500, DRM_SHMOBILE, DRM_NOUVEAU, DRM_FSL_DCU, DRM_I915, DRM_RADEON, DRM_AMDGPU, DRM_PARADE_PS8622
Documentation/kbuild/kconfig-language.txt has a note regarding select: 1. 'select should be used with care since it doesn't visit dependencies.' This is not a problem since BACKLIGHT_CLASS_DEVICE doesn't have any dependencies. 2. 'In general use select only for non-visible symbols' BACKLIGHT_CLASS_DEVICE is user visible.
The real solution to this would be to have DRM_KMS_FB_HELPER depend on the user visible symbol FB. That is a can of worms I'm not willing to tackle. I fear that such a change will result in me handling difficult fallouts for the next weeks. So I'm following DRM suite here.
Signed-off-by: Noralf Trønnes noralf@tronnes.org Reviewed-by: David Lechner david@lechnology.com Link: https://patchwork.freedesktop.org/patch/msgid/20190722104312.16184-7-noralf@... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/tinydrm/Kconfig | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/tinydrm/Kconfig b/drivers/gpu/drm/tinydrm/Kconfig index 87819c82bcce8..f2f0739d1035d 100644 --- a/drivers/gpu/drm/tinydrm/Kconfig +++ b/drivers/gpu/drm/tinydrm/Kconfig @@ -14,8 +14,8 @@ config TINYDRM_MIPI_DBI config TINYDRM_HX8357D tristate "DRM support for HX8357D display panels" depends on DRM_TINYDRM && SPI - depends on BACKLIGHT_CLASS_DEVICE select TINYDRM_MIPI_DBI + select BACKLIGHT_CLASS_DEVICE help DRM driver for the following HX8357D panels: * YX350HV15-T 3.5" 340x350 TFT (Adafruit 3.5") @@ -35,8 +35,8 @@ config TINYDRM_ILI9225 config TINYDRM_ILI9341 tristate "DRM support for ILI9341 display panels" depends on DRM_TINYDRM && SPI - depends on BACKLIGHT_CLASS_DEVICE select TINYDRM_MIPI_DBI + select BACKLIGHT_CLASS_DEVICE help DRM driver for the following Ilitek ILI9341 panels: * YX240QV29-T 2.4" 240x320 TFT (Adafruit 2.4") @@ -46,8 +46,8 @@ config TINYDRM_ILI9341 config TINYDRM_MI0283QT tristate "DRM support for MI0283QT" depends on DRM_TINYDRM && SPI - depends on BACKLIGHT_CLASS_DEVICE select TINYDRM_MIPI_DBI + select BACKLIGHT_CLASS_DEVICE help DRM driver for the Multi-Inno MI0283QT display panel If M is selected the module will be called mi0283qt. @@ -78,8 +78,8 @@ config TINYDRM_ST7586 config TINYDRM_ST7735R tristate "DRM support for Sitronix ST7735R display panels" depends on DRM_TINYDRM && SPI - depends on BACKLIGHT_CLASS_DEVICE select TINYDRM_MIPI_DBI + select BACKLIGHT_CLASS_DEVICE help DRM driver Sitronix ST7735R with one of the following LCDs: * JD-T18003-T01 1.8" 128x160 TFT