kdrive: Don't enable drm master by default

On some cards, `drmSetMaster` hangs.

Since Xfbdev does not set the video card mode, it does not need
master permissions. As such, we can just drop master at the
begining to not conflict with other drm users.

For any cards that do require master permissions,
Xfbdev can still do the `drm{Set,Drop}Master` dance
on {Enter,Leave}VT, with a command line argument.

Fixes: https://github.com/X11Libre/xserver/issues/2711

Signed-off-by: stefan11111 <stefan11111github@gmail.com>

hw/kdrive/fbdev/fb_glamor.c

@@ -22,10 +22,13 @@
 #include <xf86drm.h>
 #endif
 
+#include <errno.h>
+
 char *fbdev_glvnd_provider = NULL;
 char *fbdev_dri_path = NULL;
 
 bool fbdev_auto_dri3 = FALSE;
+bool fbdev_drm_master = FALSE;
 bool es_allowed = TRUE;
 bool force_es = FALSE;
 bool fbGlamorAllowed = TRUE;
@@ -43,10 +46,14 @@ fbdevInitAccel(ScreenPtr pScreen)
         scrpriv->dri_fd = open(fbdev_dri_path, O_RDWR);
         if (scrpriv->dri_fd >= 0) {
 #ifdef WITH_LIBDRM
-            drmSetMaster(scrpriv->dri_fd);
+            if (fbdev_drm_master) {
+                drmSetMaster(scrpriv->dri_fd);
+            } else {
+                drmDropMaster(scrpriv->dri_fd);
+            }
 #endif
         } else {
-            perror("open");
+            LogMessage(X_WARNING, "Could not open %s: %s\n", fbdev_dri_path, strerror(errno));
         }
     } else {
         scrpriv->dri_fd = -1;
@@ -115,7 +122,7 @@ fbdevEnableAccel(ScreenPtr pScreen)
     KdScreenInfo *screen = pScreenPriv->screen;
     FbdevScrPriv *scrpriv = screen->driver;
 
-    if (scrpriv->dri_fd >= 0) {
+    if (fbdev_drm_master && scrpriv->dri_fd >= 0) {
         drmSetMaster(scrpriv->dri_fd);
     }
 #endif
@@ -129,7 +136,7 @@ fbdevDisableAccel(ScreenPtr pScreen)
     KdScreenInfo *screen = pScreenPriv->screen;
     FbdevScrPriv *scrpriv = screen->driver;
 
-    if (scrpriv->dri_fd >= 0) {
+    if (fbdev_drm_master && scrpriv->dri_fd >= 0) {
         drmDropMaster(scrpriv->dri_fd);
     }
 #endif

hw/kdrive/fbdev/fbdev.h

@@ -60,6 +60,7 @@ extern Bool fbDisableShadow;
 extern char *fbdev_glvnd_provider;
 extern char *fbdev_dri_path;
 extern bool fbdev_auto_dri3;
+extern bool fbdev_drm_master;
 extern bool es_allowed;
 extern bool force_es;
 extern bool fbGlamorAllowed;

hw/kdrive/fbdev/fbinit.c

@@ -72,6 +72,8 @@ ddxUseMsg(void)
         ("-fb path         Framebuffer device to use. Defaults to /dev/fb0\n");
     ErrorF
         ("-dri <path|auto> Optional drm device path to use\n");
+    ErrorF
+        ("-drm-master      Enable master permissions on the fd used for dri\n");
     ErrorF
         ("-noshadow        Disable the ShadowFB layer if possible\n");
     ErrorF
@@ -140,6 +142,11 @@ ddxProcessArgument(int argc, char **argv, int i)
         }
     }
 
+    if (!strcmp(argv[i], "-drm-master")) {
+        fbdev_drm_master = TRUE;
+        return 1;
+    }
+
     if (!strcmp(argv[i], "-force-gl")) {
         es_allowed = FALSE;
         return 1;