[PATCH v9 6/6] drm_modes: add of_videomode helpers

[Steffen Trumtrar <s.trumtrar@pengutronix.de>]

Add helper to get drm_display_mode from devicetree.

Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
---
 drivers/gpu/drm/drm_modes.c |   35 ++++++++++++++++++++++++++++++++++-
 include/drm/drmP.h          |    6 ++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 42ea099..c3ae5d2 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -35,7 +35,8 @@
 #include <linux/export.h>
 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
-#include <linux/videomode.h>
+#include <linux/of.h>
+#include <linux/of_videomode.h>
 
 /**
  * drm_mode_debug_printmodeline - debug print a mode
@@ -540,6 +541,38 @@ int display_mode_from_videomode(struct videomode *vm, struct drm_display_mode *d
 EXPORT_SYMBOL_GPL(display_mode_from_videomode);
 #endif
 
+#if IS_ENABLED(CONFIG_OF_VIDEOMODE)
+/**
+ * of_get_drm_display_mode - get a drm_display_mode from devicetree
+ * @np: device_node with the timing specification
+ * @dmode: will be set to the return value
+ * @index: index into the list of display timings in devicetree
+ *
+ * This function is expensive and should only be used, if only one mode is to be
+ * read from DT. To get multiple modes start with of_get_display_timings and
+ * work with that instead.
+ */
+int of_get_drm_display_mode(struct device_node *np, struct drm_display_mode *dmode,
+			unsigned int index)
+{
+	struct videomode vm;
+	int ret;
+
+	ret = of_get_videomode(np, &vm, index);
+	if (ret)
+		return ret;
+
+	display_mode_from_videomode(&vm, dmode);
+
+	pr_info("%s: got %dx%d display mode from %s\n", __func__, vm.hactive,
+		vm.vactive, np->name);
+	drm_mode_debug_printmodeline(dmode);
+
+	return 0;
+
+}
+EXPORT_SYMBOL_GPL(of_get_drm_display_mode);
+#endif
 /**
  * drm_mode_set_name - set the name on a mode
  * @mode: name will be set in this mode
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 1e0d846..e8f46a1 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -56,6 +56,7 @@
 #include <linux/cdev.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
+#include <linux/of.h>
 #include <linux/videomode.h>
 #if defined(__alpha__) || defined(__powerpc__)
 #include <asm/pgtable.h>	/* For pte_wrprotect */
@@ -1459,6 +1460,11 @@ drm_mode_create_from_cmdline_mode(struct drm_device *dev,
 extern int display_mode_from_videomode(struct videomode *vm,
 				       struct drm_display_mode *dmode);
 #endif
+#if IS_ENABLED(CONFIG_OF_VIDEOMODE)
+extern int of_get_drm_display_mode(struct device_node *np,
+				   struct drm_display_mode *dmode,
+				   unsigned int index);
+#endif
 
 /* Modesetting support */
 extern void drm_vblank_pre_modeset(struct drm_device *dev, int crtc);
-- 
1.7.10.4