DRI3: Allow specifying "auto" as DRM render node

(This works identically to '-rendernode auto' in TigerVNC.)

unix/Xvnc/programs/Xserver/Xvnc.man.in

@@ -266,7 +266,8 @@ Set the color depth of the virtual X display, in bits per pixel. Must be 8,
 Enable the DRI3 X extension, which provides GPU acceleration for OpenGL and
 other rendering APIs when using open source GPU drivers. \fIrender-node\fR is
 the path of the DRM render node for the GPU that you wish to use (for example,
-\fB/dev/dri/renderD128\fR).
+\fB/dev/dri/renderD128\fR). If \fIrender-node\fR is \fBauto\fR, then the first
+available DRM render node will be used.
 
 .TP
 \fB\-geometry\fR \fIwidth\fRx\fIheight\fR

unix/Xvnc/programs/Xserver/hw/vnc/dri3.c

@@ -26,6 +26,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <glob.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
@@ -459,6 +460,37 @@ Bool rfbDRI3Initialize(ScreenPtr pScreen)
  pScreenPriv->gbm = NULL;
  pScreenPriv->fd = -1;
 
+ if (strcasecmp(driNode, "auto") == 0) {
+ glob_t globbuf;
+ int ret;
+ size_t i;
+
+ ret = glob("/dev/dri/renderD*", 0, NULL, &globbuf);
+ if (ret == GLOB_NOMATCH) {
+ ErrorF("Could not find any DRM render nodes\n");
+ return FALSE;
+ }
+ if (ret != 0) {
+ ErrorF("Could not enumerate DRM render nodes\n");
+ return FALSE;
+ }
+
+ driNode = NULL;
+ for (i = 0; i < globbuf.gl_pathc; i++) {
+ if (access(globbuf.gl_pathv[i], R_OK | W_OK) == 0) {
+ driNode = strdup(globbuf.gl_pathv[i]);
+ break;
+ }
+ }
+
+ globfree(&globbuf);
+
+ if (driNode == NULL) {
+ ErrorF("Could not find any available DRM render nodes\n");
+ return FALSE;
+ }
+ }
+
  pScreenPriv->fd = open(driNode, O_RDWR | O_CLOEXEC);
  if (pScreenPriv->fd < 0) {
  ErrorF("Failed to open DRM render node %s\n", driNode);
@@ -474,6 +506,8 @@ Bool rfbDRI3Initialize(ScreenPtr pScreen)
  DRI3_WRAP(CloseScreen, rfbDRI3CloseScreen)
  DRI3_WRAP(DestroyPixmap, rfbDRI3DestroyPixmap)
 
+ rfbLog("Using DRM render node %s for DRI3\n", driNode);
+
  return dri3_screen_init(pScreen, &rfbDRI3ScreenInfo);
 }