[PATCH xserver] glamor_egl: request GL2.1 when requesting Desktop GL context

[Icenowy Zheng]

Some devices cannot support OpenGL 2.1, which is the minimum desktop GL
version required by glamor. However, they may support OpenGL ES 2.0,
which is the GLES version required by glamor. Usually in this situation
the desktop GL version supported is 2.0 or 1.4.

Currently, as no requirements are passed when creating desktop GL
context, a OpenGL 1.4/2.0 context will be created, and glamor will
arguing that the context is not suitable, although the GPU supports a
suitable GLES context.

Add version number 2.1 requirement when requesting non-core desktop GL
context (core context has at least 3.1), so it will fall back to create
GLES contexts when the version number requirement is not met.

Tested on a Intel 945GMS integrated GPU, which supports GL 1.4 and GLES
2.0. Before applying this, it will fail to launch X server when no
configuration is present because of glamor initialization failure, after
applying glamor will start with GLES.

Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
---
 glamor/glamor.h     | 4 ++++
 glamor/glamor_egl.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/glamor/glamor.h b/glamor/glamor.h
index 09e9c895c..abee6a3e8 100644
--- a/glamor/glamor.h
+++ b/glamor/glamor.h
@@ -75,6 +75,10 @@ typedef Bool (*GetDrawableModifiersFuncPtr) (DrawablePtr draw,
 #define GLAMOR_GL_CORE_VER_MAJOR 3
 #define GLAMOR_GL_CORE_VER_MINOR 1
 
+/* We need OpenGL 2.1 to work at least */
+#define GLAMOR_GL_VER_MAJOR 2
+#define GLAMOR_GL_VER_MINOR 1
+
 /* @glamor_init: Initialize glamor internal data structure.
  *
  * @screen: Current screen pointer.
diff --git a/glamor/glamor_egl.c b/glamor/glamor_egl.c
index b33d8ef15..8da8d2731 100644
--- a/glamor/glamor_egl.c
+++ b/glamor/glamor_egl.c
@@ -946,6 +946,10 @@ glamor_egl_init(ScrnInfoPtr scrn, int fd)
             EGL_NONE
         };
         static const EGLint config_attribs[] = {
+            EGL_CONTEXT_MAJOR_VERSION_KHR,
+	    GLAMOR_GL_VER_MAJOR,
+	    EGL_CONTEXT_MINOR_VERSION_KHR,
+	    GLAMOR_GL_VER_MINOR,
             EGL_NONE
         };
 
-- 
2.18.0