efifb: BGRT: Do not copy the boot graphics for non native resolutions

@@ -111,6 +111,46 @@ static void efifb_copy_bmp(u8 *src, u32 *dst, int width, struct screen_info *si)
 	}
 }
 
+#ifdef CONFIG_X86
+/*
+ * On x86 some firmwares use a low non native resolution for the display when
+ * they have shown some text messages. While keeping the bgrt filled with info
+ * for the native resolution. If the bgrt image intended for the native
+ * resolution still fits, it will be displayed very close to the right edge of
+ * the display looking quite bad. This function checks for this.
+ */
+static bool efifb_bgrt_sanity_check(struct screen_info *si, u32 bmp_width)
+{
+	static const int default_resolutions[][2] = {
+		{  800,  600 },
+		{ 1024,  768 },
+		{ 1280, 1024 },
+	};
+	u32 i, right_margin;
+
+	for (i = 0; i < ARRAY_SIZE(default_resolutions); i++) {
+		if (default_resolutions[i][0] = si->lfb_width &&
+		    default_resolutions[i][1] = si->lfb_height)
+			break;
+	}
+	/* If not a default resolution used for textmode, this should be fine */
+	if (i >= ARRAY_SIZE(default_resolutions))
+		return true;
+
+	/* If the right margin is 5 times smaller then the left one, reject */
+	right_margin = si->lfb_width - (bgrt_tab.image_offset_x + bmp_width);
+	if (right_margin < (bgrt_tab.image_offset_x / 5))
+		return false;
+
+	return true;
+}
+#else
+static bool efifb_bgrt_sanity_check(struct screen_info *si, u32 bmp_width)
+{
+	return true;
+}
+#endif
+
 static void efifb_show_boot_graphics(struct fb_info *info)
 {
 	u32 bmp_width, bmp_height, bmp_pitch, screen_pitch, dst_x, y, src_y;

@@ -169,6 +209,9 @@ static void efifb_show_boot_graphics(struct fb_info *info)
 	    (bgrt_tab.image_offset_y + bmp_height) > si->lfb_height)
 		goto error;
 
+	if (!efifb_bgrt_sanity_check(si, bmp_width))
+		goto error;
+
 	pr_info("efifb: showing boot graphics\n");
 
 	for (y = 0; y < si->lfb_height; y++, dst += si->lfb_linelength) {