drm/modes: Make sure to parse valid rotation value from cmdline

A rotation value should have exactly one rotation angle.
At the moment there is no validation for this when parsing video=
parameters from the command line. This causes problems later on
when we try to combine the command line rotation with the panel
orientation.

To make sure that we generate a valid rotation value:
  - Set DRM_MODE_ROTATE_0 by default (if no rotate= option is set)
  - Validate that there is exactly one rotation angle set
    (i.e. specifying the rotate= option multiple times is invalid)
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20200117153429.54700-2-stephan@gerhold.net

drivers/gpu/drm/drm_modes.c

@@ -1698,6 +1698,13 @@ static int drm_mode_parse_cmdline_options(const char *str,
 	if (rotation && freestanding)
 		return -EINVAL;
 
+	if (!(rotation & DRM_MODE_ROTATE_MASK))
+		rotation |= DRM_MODE_ROTATE_0;
+
+	/* Make sure there is exactly one rotation defined */
+	if (!is_power_of_2(rotation & DRM_MODE_ROTATE_MASK))
+		return -EINVAL;
+
 	mode->rotation_reflection = rotation;
 
 	return 0;

drivers/gpu/drm/selftests/drm_cmdline_selftests.h

@@ -53,6 +53,7 @@ cmdline_test(drm_cmdline_test_rotate_0)
 cmdline_test(drm_cmdline_test_rotate_90)
 cmdline_test(drm_cmdline_test_rotate_180)
 cmdline_test(drm_cmdline_test_rotate_270)
+cmdline_test(drm_cmdline_test_rotate_multiple)
 cmdline_test(drm_cmdline_test_rotate_invalid_val)
 cmdline_test(drm_cmdline_test_rotate_truncated)
 cmdline_test(drm_cmdline_test_hmirror)

drivers/gpu/drm/selftests/test-drm_cmdline_parser.c

@@ -856,6 +856,17 @@ static int drm_cmdline_test_rotate_270(void *ignored)
 	return 0;
 }
 
+static int drm_cmdline_test_rotate_multiple(void *ignored)
+{
+	struct drm_cmdline_mode mode = { };
+
+	FAIL_ON(drm_mode_parse_command_line_for_connector("720x480,rotate=0,rotate=90",
+							  &no_connector,
+							  &mode));
+
+	return 0;
+}
+
 static int drm_cmdline_test_rotate_invalid_val(void *ignored)
 {
 	struct drm_cmdline_mode mode = { };
@@ -888,7 +899,7 @@ static int drm_cmdline_test_hmirror(void *ignored)
 	FAIL_ON(!mode.specified);
 	FAIL_ON(mode.xres != 720);
 	FAIL_ON(mode.yres != 480);
-	FAIL_ON(mode.rotation_reflection != DRM_MODE_REFLECT_X);
+	FAIL_ON(mode.rotation_reflection != (DRM_MODE_ROTATE_0 | DRM_MODE_REFLECT_X));
 
 	FAIL_ON(mode.refresh_specified);
 
@@ -913,7 +924,7 @@ static int drm_cmdline_test_vmirror(void *ignored)
 	FAIL_ON(!mode.specified);
 	FAIL_ON(mode.xres != 720);
 	FAIL_ON(mode.yres != 480);
-	FAIL_ON(mode.rotation_reflection != DRM_MODE_REFLECT_Y);
+	FAIL_ON(mode.rotation_reflection != (DRM_MODE_ROTATE_0 | DRM_MODE_REFLECT_Y));
 
 	FAIL_ON(mode.refresh_specified);