xf86/logind: Fix drm_drop_master before vt_reldisp

When switching to VT, the ioctl DRM_DROP_MASTER must be done before
the ioctl VT_RELDISP. Otherwise the kernel can't change the modesetting
reliably, and this leads to the console not showing up in some cases, like
after unplugging a docking station with a DP or HDMI monitor.

Before doing the VT_RELDISP, send a dbus message to logind, to
pause the drm device, so logind will do the ioctl DRM_DROP_MASTER.

With this patch, it changes the order logind will send the resume
event, and drm will be sent last instead of first.
so there is a also fix to call systemd_logind_vtenter() at the right time.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>

hw/xfree86/common/xf86Events.c

@@ -382,6 +382,17 @@ xf86VTLeave(void)
     for (i = 0; i < xf86NumGPUScreens; i++)
         xf86GPUScreens[i]->LeaveVT(xf86GPUScreens[i]);
 
+    if (systemd_logind_controls_session()) {
+        for (i = 0; i < xf86_num_platform_devices; i++) {
+            if (xf86_platform_devices[i].flags & XF86_PDEV_SERVER_FD) {
+                int major, minor;
+                major = xf86_platform_odev_attributes(i)->major;
+                minor = xf86_platform_odev_attributes(i)->minor;
+                systemd_logind_drop_master(major, minor);
+            }
+        }
+    }
+
     if (!xf86VTSwitchAway())
         goto switch_failed;
 

hw/xfree86/os-support/linux/systemd-logind.c

@@ -303,6 +303,20 @@ cleanup:
     dbus_error_free(&error);
 }
 
+/*
+ * Send a message to logind, to pause the drm device
+ * and ensure the drm_drop_master is done before
+ * VT_RELDISP when switching VT
+ */
+void systemd_logind_drop_master(int _major, int _minor)
+{
+    struct systemd_logind_info *info = &logind_info;
+    dbus_int32_t major = _major;
+    dbus_int32_t minor = _minor;
+
+    systemd_logind_ack_pause(info, minor, major);
+}
+
 static DBusHandlerResult
 message_filter(DBusConnection * connection, DBusMessage * message, void *data)
 {

include/systemd-logind.h

@@ -33,6 +33,7 @@ int systemd_logind_take_fd(int major, int minor, const char *path, Bool *paus);
 void systemd_logind_release_fd(int major, int minor, int fd);
 int systemd_logind_controls_session(void);
 void systemd_logind_vtenter(void);
+void systemd_logind_drop_master(int major, int minor);
 #else
 #define systemd_logind_init()
 #define systemd_logind_fini()
@@ -40,6 +41,7 @@ void systemd_logind_vtenter(void);
 #define systemd_logind_release_fd(major, minor, fd) close(fd)
 #define systemd_logind_controls_session() 0
 #define systemd_logind_vtenter()
+#define systemd_logind_drop_master(major, minor)
 #endif
 
 #endif