[PATCH 5/5] drm: add config option for extra build-time checks

[Jani Nikula <jani.nikula@intel.com>]

The DRM subsystem contains additional build-time checks, primarily aimed
at DRM developers and CI systems. The checks may be overzealous. They
may slow down or fail the build altogether. They may create excessive
dependency files in the build tree. They should not be enabled for
regular builds, and certainly not forced on unsuspecting developers
running an allyesconfig or allmodconfig build.

Add config DRM_DISABLE_EXTRA_BUILD_CHECKS, enabled by default as well as
by allyesconfig/allmodconfig, hiding the extra checks from anyone but
people who intentionally opt-in for the checks.

For example, to enable header tests:

$ scripts/config --disable CONFIG_DRM_DISABLE_EXTRA_BUILD_CHECKS --enable CONFIG_DRM_HEADER_TEST
$ make olddefconfig

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/r/CAHk-=wjcdfrDTjzm6J6T-3fxtVyBG7a_0BXc2=mgOuM6KPFnCg@mail.gmail.com
Fixes: 62ae45687e43 ("drm: ensure drm headers are self-contained and pass kernel-doc")
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

Cc: linux-kbuild@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: intel-xe@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
---
 drivers/gpu/drm/Kconfig | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 2cba2b6ebe1c..5a3fce9ef998 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -489,9 +489,26 @@ config DRM_PRIVACY_SCREEN
 	bool
 	default n
 
+# Reversed option to disable on allyesconfig/allmodconfig builds
+config DRM_DISABLE_EXTRA_BUILD_CHECKS
+	bool "Disable DRM subsystem extra build-time checks"
+	default y
+	help
+	  The DRM subsystem contains additional build-time checks, primarily
+	  aimed at DRM developers and CI systems. The checks may be
+	  overzealous. They may slow down or fail the build altogether. They may
+	  create excessive dependency files in the tree. They should not be
+	  enabled for regular builds, and thus they are disabled by default.
+
+# Proxy config to allow simple "depends on DRM_EXTRA_BUILD_CHECKS"
+config DRM_EXTRA_BUILD_CHECKS
+	bool
+	depends on DRM && EXPERT && DRM_DISABLE_EXTRA_BUILD_CHECKS=n
+	default !DRM_DISABLE_EXTRA_BUILD_CHECKS
+
 config DRM_WERROR
 	bool "Compile the drm subsystem with warnings as errors"
-	depends on DRM && EXPERT
+	depends on DRM_EXTRA_BUILD_CHECKS
 	depends on !WERROR
 	default n
 	help
@@ -505,7 +522,7 @@ config DRM_WERROR
 
 config DRM_HEADER_TEST
 	bool "Ensure DRM headers are self-contained and pass kernel-doc"
-	depends on DRM && EXPERT && BROKEN
+	depends on DRM_EXTRA_BUILD_CHECKS
 	default n
 	help
 	  Ensure the DRM subsystem headers both under drivers/gpu/drm and
-- 
2.39.5