[PATCH xserver] glamor: glamor_egl_get_display: Return NULL if eglGetPlatformDisplayEXT returns NULL

[Hans de Goede]

If the libEGL we are using has eglGetPlatformDisplayEXT, yet it still
returns NULL, then this very likely means that it does not support
the type (e.g. EGL_PLATFORM_GBM_MESA) passed in, and then returning NULL
is the right thing to do.

This avoids falling back to an eglGetDisplay() implementation which does
not understands the passed in gbm handle, treats it as a pointer to
something else completely, followed by a crash sooner or later.

Specifically this fixes using the nvidia binary driver, with nvidia's
libEGL + the modesetting driver on a secondary GPU crashing inside
glamor_egl_init() sometimes.

Cc: Adam Jackson <ajax at redhat.com>
Cc: Eric Anholt <eric at anholt.net>
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 glamor/glamor_egl.c | 4 ++++
 glamor/glamor_egl.h | 4 +---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/glamor/glamor_egl.c b/glamor/glamor_egl.c
index 9cc0f8d..4bde637 100644
--- a/glamor/glamor_egl.c
+++ b/glamor/glamor_egl.c
@@ -769,6 +769,10 @@ glamor_egl_init(ScrnInfoPtr scrn, int fd)
 
     glamor_egl->display = glamor_egl_get_display(EGL_PLATFORM_GBM_MESA,
                                                  glamor_egl->gbm);
+    if (!glamor_egl->display) {
+        xf86DrvMsg(scrn->scrnIndex, X_ERROR, "eglGetDisplay() failed\n");
+        goto error;
+    }
 #else
     glamor_egl->display = eglGetDisplay((EGLNativeDisplayType) (intptr_t) fd);
 #endif
diff --git a/glamor/glamor_egl.h b/glamor/glamor_egl.h
index 6b05f57..2c6d307 100644
--- a/glamor/glamor_egl.h
+++ b/glamor/glamor_egl.h
@@ -67,9 +67,7 @@ glamor_egl_get_display(EGLint type, void *native)
         PFNEGLGETPLATFORMDISPLAYEXTPROC getPlatformDisplayEXT =
             (void *) eglGetProcAddress("eglGetPlatformDisplayEXT");
         if (getPlatformDisplayEXT)
-            dpy = getPlatformDisplayEXT(type, native, NULL);
-        if (dpy)
-            return dpy;
+            return getPlatformDisplayEXT(type, native, NULL);
     }
 
     /* Welp, everything is awful. */
-- 
2.9.3