kdrive/fbdev: Don't try to accelerate rendering with glamor with a sw driver

It will likely be slower that unaccelerated rendering.
Command-line flags were added for overriding this.

Signed-off-by: stefan11111 <stefan11111@shitposting.expert>

hw/kdrive/fbdev/fb_glamor.c

@@ -24,6 +24,8 @@ char *fbdev_glvnd_provider = NULL;
 
 Bool es_allowed = TRUE;
 Bool force_es = FALSE;
+Bool fbGlamorAllowed = TRUE;
+Bool fbForceGlamor = FALSE;
 Bool fbXVAllowed = TRUE;
 
 static void
@@ -97,7 +99,19 @@ fbdevInitAccel(ScreenPtr pScreen)
         return FALSE;
     }
 
-    if (!glamor_init(pScreen, GLAMOR_USE_EGL_SCREEN | GLAMOR_NO_DRI3)) {
+    int flags = GLAMOR_USE_EGL_SCREEN | GLAMOR_NO_DRI3;
+    if (!fbGlamorAllowed) {
+        flags |= GLAMOR_NO_RENDER_ACCEL;
+    } else if (!fbForceGlamor){
+        const char *renderer = (const char*)glGetString(GL_RENDERER);
+        if (!renderer ||
+            strstr(renderer, "softpipe") ||
+            strstr(renderer, "llvmpipe")) {
+            flags |= GLAMOR_NO_RENDER_ACCEL;
+        }
+    }
+
+    if (!glamor_init(pScreen, flags)) {
         fbdev_glamor_egl_cleanup(scrpriv);
         return FALSE;
     }
@@ -112,7 +126,8 @@ fbdevInitAccel(ScreenPtr pScreen)
 #endif
 
 #ifdef XV
-    if (fbXVAllowed) {
+    /* X-Video needs glamor render accel */
+    if (fbXVAllowed && !(flags & GLAMOR_NO_RENDER_ACCEL)) {
         kd_glamor_xv_init(pScreen);
     }
 #endif

hw/kdrive/fbdev/fbdev.h

@@ -66,6 +66,8 @@ extern Bool fbDisableShadow;
 extern char *fbdev_glvnd_provider;
 extern Bool es_allowed;
 extern Bool force_es;
+extern Bool fbGlamorAllowed;
+extern Bool fbForceGlamor;
 #ifdef XV
 extern Bool fbXVAllowed;
 #endif

hw/kdrive/fbdev/fbinit.c

@@ -72,6 +72,10 @@ ddxUseMsg(void)
         ("-fb path         Framebuffer device to use. Defaults to /dev/fb0\n");
     ErrorF
         ("-noshadow        Disable the ShadowFB layer if possible\n");
+    ErrorF
+        ("-glamor          Force enable glamor render acceleration if possible\n");
+    ErrorF
+        ("-noglamor        Force disable glamor render acceleration\n");
     ErrorF
         ("-glvendor        Suggest what glvnd vendor library should be used\n");
     ErrorF
@@ -101,6 +105,16 @@ ddxProcessArgument(int argc, char **argv, int i)
     }
 
 #ifdef GLAMOR
+    if (!strcmp(argv[i], "-glamor")) {
+        fbForceGlamor = TRUE;
+        return 1;
+    }
+
+    if (!strcmp(argv[i], "-noglamor")) {
+        fbGlamorAllowed = FALSE;
+        return 1;
+    }
+
     if (!strcmp(argv[i], "-glvendor")) {
         if (i + 1 < argc) {
             fbdev_glvnd_provider = strdup(argv[i + 1]);