3389669ac5
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@tronnes.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.