drm: add DRM_CAPs for cursor size

Some hardware may not support standard 64x64 cursors.  Add
a drm cap to query the cursor size from the kernel.  Some examples
include radeon CIK parts (128x128 cursors) and armada (32x64 or 64x32).
This allows things like device specific ddxes to remove asics specific
logic and also allows xf86-video-modesetting to work properly with hw
cursors on this hardware. Default to 64 if the driver doesn't specify
a size.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>
Reviewed-by: NRob Clark <robdclark@gmail.com>

drivers/gpu/drm/drm_ioctl.c

@@ -296,6 +296,18 @@ int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_priv)
 	case DRM_CAP_ASYNC_PAGE_FLIP:
 		req->value = dev->mode_config.async_page_flip;
 		break;
+	case DRM_CAP_CURSOR_WIDTH:
+		if (dev->mode_config.cursor_width)
+			req->value = dev->mode_config.cursor_width;
+		else
+			req->value = 64;
+		break;
+	case DRM_CAP_CURSOR_HEIGHT:
+		if (dev->mode_config.cursor_height)
+			req->value = dev->mode_config.cursor_height;
+		else
+			req->value = 64;
+		break;
 	default:
 		return -EINVAL;
 	}

include/drm/drm_crtc.h

@@ -907,6 +907,9 @@ struct drm_mode_config {
 
 	/* whether async page flip is supported or not */
 	bool async_page_flip;
+
+	/* cursor size */
+	uint32_t cursor_width, cursor_height;
 };
 
 #define obj_to_crtc(x) container_of(x, struct drm_crtc, base)

include/uapi/drm/drm.h

@@ -619,6 +619,8 @@ struct drm_gem_open {
 #define  DRM_PRIME_CAP_EXPORT		0x2
 #define DRM_CAP_TIMESTAMP_MONOTONIC	0x6
 #define DRM_CAP_ASYNC_PAGE_FLIP		0x7
+#define DRM_CAP_CURSOR_WIDTH		0x8
+#define DRM_CAP_CURSOR_HEIGHT		0x9
 
 /** DRM_IOCTL_GET_CAP ioctl argument type */
 struct drm_get_cap {