2 files changed, 46 insertions, 0 deletions

diff --git a/drivers/video/fbmon.c b/drivers/video/fbmon.c
index 17ce135a18fd..94ad0f71383c 100644
--- a/drivers/video/fbmon.c
+++ b/drivers/video/fbmon.c
@@ -31,6 +31,7 @@
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <video/edid.h>
+#include <video/of_videomode.h>
 #include <video/videomode.h>
 #ifdef CONFIG_PPC_OF
 #include <asm/prom.h>
@@ -1425,6 +1426,47 @@ int fb_videomode_from_videomode(const struct videomode *vm,
 EXPORT_SYMBOL_GPL(fb_videomode_from_videomode);
 #endif
 
+#if IS_ENABLED(CONFIG_OF_VIDEOMODE)
+static inline void dump_fb_videomode(const struct fb_videomode *m)
+{
+        pr_debug("fb_videomode = %ux%u@%uHz (%ukHz) %u %u %u %u %u %u %u %u %u\n",
+                 m->xres, m->yres, m->refresh, m->pixclock, m->left_margin,
+                 m->right_margin, m->upper_margin, m->lower_margin,
+                 m->hsync_len, m->vsync_len, m->sync, m->vmode, m->flag);
+}
+
+/**
+ * of_get_fb_videomode - get a fb_videomode from devicetree
+ * @np: device_node with the timing specification
+ * @fb: will be set to the return value
+ * @index: index into the list of display timings in devicetree
+ *
+ * DESCRIPTION:
+ * 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 ond
+ * work with that instead.
+ */
+int of_get_fb_videomode(struct device_node *np, struct fb_videomode *fb,
+                        int index)
+{
+        struct videomode vm;
+        int ret;
+
+        ret = of_get_videomode(np, &vm, index);
+        if (ret)
+                return ret;
+
+        fb_videomode_from_videomode(&vm, fb);
+
+        pr_debug("%s: got %dx%d display mode from %s\n",
+                of_node_full_name(np), vm.hactive, vm.vactive, np->name);
+        dump_fb_videomode(fb);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(of_get_fb_videomode);
+#endif
+
 #else
 int fb_parse_edid(unsigned char *edid, struct fb_var_screeninfo *var)
 {
diff --git a/include/linux/fb.h b/include/linux/fb.h
index 100a1765b787..58b98606ac26 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h
@@ -20,6 +20,7 @@ struct fb_info;
 struct device;
 struct file;
 struct videomode;
+struct device_node;
 
 /* Definitions below are used in the parsed monitor specs */
 #define FB_DPMS_ACTIVE_OFF      1
@@ -715,6 +716,9 @@ extern void fb_destroy_modedb(struct fb_videomode *modedb);
 extern int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb);
 extern unsigned char *fb_ddc_read(struct i2c_adapter *adapter);
 
+extern int of_get_fb_videomode(struct device_node *np,
+                               struct fb_videomode *fb,
+                               int index);
 extern int fb_videomode_from_videomode(const struct videomode *vm,
                                        struct fb_videomode *fbmode);