[Buildroot] [PATCH 1/1] package/qt6/qt6base: don't require gbm for eglfs

[Fred Lefranc <fred.lefranc.evs@gmail.com>]

From: Fred Lefranc <fred.lefranc+evs@gmail.com>

BR2_PACKAGE_QT6BASE_EGLFS currently has a hard "depends on
BR2_PACKAGE_HAS_LIBGBM", and qt6base.mk unconditionally adds libgbm
and libdrm to QT6BASE_DEPENDENCIES whenever eglfs is enabled. This is
incorrect: GBM is only needed by the eglfs_kms backend. Other eglfs
device integrations, such as the Vivante framebuffer backend
(eglfs_viv) used on 32-bit i.MX6, provide EGL and OpenGL ES without
GBM or DRM.

As a result, eglfs cannot be enabled on i.MX6 (imx-gpu-viv only
provides libgbm on the aarch64/i.MX8 blobs), and forcing it through
triggers the dependency-chain consistency check:

  package 'qt6base' has added 'libgbm' to its _DEPENDENCIES variable
  without selecting it or depending on it from Config.in.

Make GBM optional for eglfs:

 - In Config.in, drop the hard dependency on BR2_PACKAGE_HAS_LIBGBM
   and keep only the libegl requirement, which every eglfs backend
   needs.

 - In qt6base.mk, only pass -DFEATURE_gbm=ON/-DFEATURE_kms=ON and add
   libgbm/libdrm to the dependencies when a gbm provider is actually
   present (BR2_PACKAGE_HAS_LIBGBM). Otherwise pass
   -DFEATURE_gbm=OFF/-DFEATURE_kms=OFF so that the eglfs_kms backend
   is simply not built, while eglfs_viv (and other vendor backends)
   still are.

This keeps eglfs_kms working unchanged on platforms that do provide
GBM (i.MX8, Raspberry Pi 4, ...) while allowing eglfs to be enabled on
GBM-less platforms such as i.MX6 with the Vivante framebuffer output.

Signed-off-by: Fred Lefranc <fred.lefranc+evs@gmail.com>
---
 package/qt6/qt6base/Config.in  |  2 +-
 package/qt6/qt6base/qt6base.mk | 12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/package/qt6/qt6base/Config.in b/package/qt6/qt6base/Config.in
index e6bb99de28..c33e078b15 100644
--- a/package/qt6/qt6base/Config.in
+++ b/package/qt6/qt6base/Config.in
@@ -74,7 +74,7 @@ comment "X.org XCB backend available if X.org is enabled"
 config BR2_PACKAGE_QT6BASE_EGLFS
 	bool "eglfs support"
 	depends on BR2_PACKAGE_HAS_LIBEGL
-	depends on BR2_PACKAGE_HAS_LIBGBM
+	depends on BR2_PACKAGE_HAS_LIBGBM || BR2_PACKAGE_IMX_GPU_VIV_OUTPUT_FB
 	depends on BR2_PACKAGE_QT6_GL_SUPPORTS
 	select BR2_PACKAGE_QT6BASE_OPENGL
 
diff --git a/package/qt6/qt6base/qt6base.mk b/package/qt6/qt6base/qt6base.mk
index 01661b7f01..5e6cf66f32 100644
--- a/package/qt6/qt6base/qt6base.mk
+++ b/package/qt6/qt6base/qt6base.mk
@@ -305,8 +305,16 @@ QT6BASE_CONF_OPTS += -DFEATURE_tslib=OFF
 endif
 
 ifeq ($(BR2_PACKAGE_QT6BASE_EGLFS),y)
-QT6BASE_CONF_OPTS += -DFEATURE_egl=ON -DFEATURE_eglfs=ON
-QT6BASE_DEPENDENCIES += libegl libgbm
+QT6BASE_CONF_OPTS   += -DINPUT_opengl=es2 -DFEATURE_egl=ON -DFEATURE_eglfs=ON
+QT6BASE_DEPENDENCIES += libegl
+
+# Only pull in GBM/KMS/DRM when a gbm provider actually exists (i.MX8, RPi, etc.)
+ifeq ($(BR2_PACKAGE_HAS_LIBGBM),y)
+QT6BASE_CONF_OPTS    += -DFEATURE_gbm=ON -DFEATURE_kms=ON
+QT6BASE_DEPENDENCIES += libgbm libdrm
+else
+QT6BASE_CONF_OPTS    += -DFEATURE_gbm=OFF -DFEATURE_kms=OFF
+endif
 else
 QT6BASE_CONF_OPTS += -DFEATURE_eglfs=OFF
 endif
-- 
2.34.1

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