Patch 5/5 modesetting: try to get gpu device fd from seatd arbiter

seatd like systemd-logind can gpu open device for us (open_hw function in
driver.c). Aditionally there are atleast two implications:
 1. During console switch the passed gpu device will receive DROP_MASTER ioctl from seatd
 2. XServer user doesn't need to have rigts to /dev/dri/card* file nodes

Signed-off-By: Tautvis <[email protected]>

Author: cepelinas9000

hw/xfree86/common/seatd-libseat.h

@@ -31,7 +31,7 @@
 #include <xf86Xinput.h>
 extern int seatd_libseat_init(BOOL KeepTty_state);
 extern void seatd_libseat_fini(void);
-extern int seatd_libseat_open_graphics(const char *path);
+extern _X_EXPORT int seatd_libseat_open_graphics(const char *path);
 extern void seatd_libseat_open_device(InputInfoPtr p,int *fd,Bool *paus);
 extern void seatd_libseat_close_device(InputInfoPtr p);
 extern int seatd_libseat_switch_session(int session);

hw/xfree86/drivers/modesetting/driver.c

@@ -66,6 +66,11 @@
 #ifdef XSERVER_LIBPCIACCESS
 #include <pciaccess.h>
 #endif
+
+#ifdef SEATD_LIBSEAT
+#include "seatd-libseat.h"
+#endif
+
 #include "driver.h"
 
 static void AdjustFrame(ScrnInfoPtr pScrn, int x, int y);
@@ -226,6 +231,28 @@ open_hw(const char *dev)
     if ((fd = get_passed_fd()) != -1)
         return fd;
 
+#ifdef SEATD_LIBSEAT
+   // try get device from seatd arbiter
+   if (dev){
+     fd = seatd_libseat_open_graphics(dev);
+     if (fd != -1){
+       return fd;
+     }
+
+   } else {
+        const char *dev_env = getenv("KMSDEVICE");
+        if (dev_env == NULL){
+            dev_env = "/dev/dri/card0";
+        }
+
+        fd = seatd_libseat_open_graphics(dev_env);
+
+        if (fd != -1) {
+          return fd;
+        }
+   }
+#endif
+
     if (dev)
         fd = open(dev, O_RDWR | O_CLOEXEC, 0);
     else {