inteldrm: add a handler for the WSDISPLAYIO_GINFO ioctl

[Frederic Cambus]

Hi tech@,

Add a handler for the WSDISPLAYIO_GINFO ioctl in inteldrm, allowing
to retrieve basic information about a framebuffer display.

When running wsconsctl on a machine with inteldrm support, this now
returns those additional fields:

display.width=1600
display.height=900
display.depth=32

Comments? OK?

Index: sys/dev/pci/drm/i915/i915_drv.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/i915/i915_drv.c,v
retrieving revision 1.101
diff -u -p -r1.101 i915_drv.c
--- sys/dev/pci/drm/i915/i915_drv.c     8 Jan 2017 12:11:54 -0000       1.101
+++ sys/dev/pci/drm/i915/i915_drv.c     17 Jun 2017 19:15:04 -0000
@@ -1037,11 +1037,20 @@ inteldrm_wsioctl(void *v, u_long cmd, ca
 {
        struct inteldrm_softc *dev_priv = v;
        struct drm_device *dev = dev_priv->dev;
+       struct rasops_info *ri = &dev_priv->ro;
+       struct wsdisplay_fbinfo *wdf;
        struct wsdisplay_param *dp = (struct wsdisplay_param *)data;
 
        switch (cmd) {
        case WSDISPLAYIO_GTYPE:
                *(int *)data = WSDISPLAY_TYPE_INTELDRM;
+               return 0;
+       case WSDISPLAYIO_GINFO:
+               wdf = (struct wsdisplay_fbinfo *)data;
+               wdf->width = ri->ri_width;
+               wdf->height = ri->ri_height;
+               wdf->depth = ri->ri_depth;
+               wdf->cmsize = 0;
                return 0;
        case WSDISPLAYIO_GETPARAM:
                if (ws_get_param && ws_get_param(dp) == 0)