drm: add a helper function to extract 'de-active' and 'pixelclk-active' from DT

add a helper function to extract information about pixel clock and DE
polarity from DT for use by of_get_drm_display_mode().
While at it, convert spaces to tabs in indentation in drm_modes.h.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index fc5040a..51804e5 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -657,6 +657,21 @@
 }
 EXPORT_SYMBOL_GPL(drm_display_mode_to_videomode);
 
+void drm_bus_flags_from_videomode(const struct videomode *vm, u32 *bus_flags)
+{
+	*bus_flags = 0;
+	if (vm->flags & DISPLAY_FLAGS_PIXDATA_POSEDGE)
+		*bus_flags |= DRM_BUS_FLAG_PIXDATA_POSEDGE;
+	if (vm->flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
+		*bus_flags |= DRM_BUS_FLAG_PIXDATA_NEGEDGE;
+
+	if (vm->flags & DISPLAY_FLAGS_DE_LOW)
+		*bus_flags |= DRM_BUS_FLAG_DE_LOW;
+	if (vm->flags & DISPLAY_FLAGS_DE_HIGH)
+		*bus_flags |= DRM_BUS_FLAG_DE_HIGH;
+}
+EXPORT_SYMBOL_GPL(drm_bus_flags_from_videomode);
+
 #ifdef CONFIG_OF
 /**
  * of_get_drm_display_mode - get a drm_display_mode from devicetree