[Mesa-stable] [PATCH] dri: Fix robust context creation via EGL attribute

[Chad Versace]

driCreateContextAttribs() emits an error if bit
__DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS is set for an ES context.  But,
EGL_EXT_create_context_robustness and EGL 1.5 both allow creation of
robust ES contexts. One requests a robust ES context by setting the
EGL_CONTEXT_OPENGL_ROBUST_ACCESS *attribute*, which Mesa's EGL layer
translates into the __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS *bit*.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
(cherry picked from commit 7a835b3fd9b171eedecfdb23d326eae4bc0cb6d4)
---
 src/mesa/drivers/dri/common/dri_util.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/common/dri_util.c b/src/mesa/drivers/dri/common/dri_util.c
index a654508..79cb050 100644
--- a/src/mesa/drivers/dri/common/dri_util.c
+++ b/src/mesa/drivers/dri/common/dri_util.c
@@ -376,11 +376,32 @@ driCreateContextAttribs(__DRIscreen *screen, int api,
      *     EGL_CONTEXT_FLAGS_KHR, then a <debug context> will be created.
      *     [...] This bit is supported for OpenGL and OpenGL ES contexts.
      *
-     * None of the other flags have any meaning in an ES context, so this seems safe.
+     * No other EGL_CONTEXT_OPENGL_*_BIT is legal for an ES context.
+     *
+     * However, Mesa's EGL layer translates the context attribute
+     * EGL_CONTEXT_OPENGL_ROBUST_ACCESS into the context flag
+     * __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS.  That attribute is legal for ES
+     * (with EGL 1.5 or EGL_EXT_create_context_robustness) and GL (only with
+     * EGL 1.5).
+     *
+     * From the EGL_EXT_create_context_robustness spec:
+     *
+     *     This extension is written against the OpenGL ES 2.0 Specification
+     *     but can apply to OpenGL ES 1.1 and up.
+     *
+     * From the EGL 1.5 (2014.08.27) spec, p55:
+     *
+     *     If the EGL_CONTEXT_OPENGL_ROBUST_ACCESS attribute is set to
+     *     EGL_TRUE, a context supporting robust buffer access will be created.
+     *     OpenGL contexts must support the GL_ARB_robustness extension, or
+     *     equivalent core API functional- ity. OpenGL ES contexts must support
+     *     the GL_EXT_robustness extension, or equivalent core API
+     *     functionality.
      */
     if (mesa_api != API_OPENGL_COMPAT
         && mesa_api != API_OPENGL_CORE
-        && (flags & ~__DRI_CTX_FLAG_DEBUG)) {
+        && (flags & ~(__DRI_CTX_FLAG_DEBUG |
+	              __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS))) {
 	*error = __DRI_CTX_ERROR_BAD_FLAG;
 	return NULL;
     }
-- 
2.8.1