drm/modes: parse_cmdline: Add support for specifying panel_orientation (v2)

Sometimes we want to override a connector's panel_orientation from the
kernel commandline. Either for testing and for special cases, e.g. a kiosk
like setup which uses a TV mounted in portrait mode.

Users can already specify a "rotate" option through a video= kernel cmdline
option. But that only supports 0/180 degrees (see drm_client_modeset TODO)
and only works for in kernel modeset clients, not for userspace kms users.

The "panel-orientation" connector property OTOH does support 90/270 degrees
as it leaves dealing with the rotation up to userspace and this does work
for userspace kms clients (at least those which support this property).

Changes in v2:
-Add missing ':' after @panel_orientation (reported by kbuild test robot)

BugLink: https://gitlab.freedesktop.org/plymouth/plymouth/merge_requests/83
Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118155134.30468-9-hdegoede@redhat.com

Documentation/fb/modedb.rst

@@ -65,6 +65,9 @@ Valid options are::
   - reflect_y (boolean): Perform an axial symmetry on the Y axis
   - rotate (integer): Rotate the initial framebuffer by x
     degrees. Valid values are 0, 90, 180 and 270.
+  - panel_orientation, one of "normal", "upside_down", "left_side_up", or
+    "right_side_up". For KMS drivers only, this sets the "panel orientation"
+    property on the kms connector as hint for kms users.
 
 
 -----------------------------------------------------------------------------

drivers/gpu/drm/drm_modes.c

@@ -1591,6 +1591,33 @@ static int drm_mode_parse_cmdline_int(const char *delim, unsigned int *int_ret)
 	return 0;
 }
 
+static int drm_mode_parse_panel_orientation(const char *delim,
+					    struct drm_cmdline_mode *mode)
+{
+	const char *value;
+
+	if (*delim != '=')
+		return -EINVAL;
+
+	value = delim + 1;
+	delim = strchr(value, ',');
+	if (!delim)
+		delim = value + strlen(value);
+
+	if (!strncmp(value, "normal", delim - value))
+		mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_NORMAL;
+	else if (!strncmp(value, "upside_down", delim - value))
+		mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_BOTTOM_UP;
+	else if (!strncmp(value, "left_side_up", delim - value))
+		mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_LEFT_UP;
+	else if (!strncmp(value, "right_side_up", delim - value))
+		mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_RIGHT_UP;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+
 static int drm_mode_parse_cmdline_options(const char *str,
 					  bool freestanding,
 					  const struct drm_connector *connector,
@@ -1657,6 +1684,9 @@ static int drm_mode_parse_cmdline_options(const char *str,
 				return -EINVAL;
 
 			mode->tv_margins.bottom = margin;
+		} else if (!strncmp(option, "panel_orientation", delim - option)) {
+			if (drm_mode_parse_panel_orientation(delim, mode))
+				return -EINVAL;
 		} else {
 			return -EINVAL;
 		}
@@ -1715,6 +1745,8 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
 	char *bpp_end_ptr = NULL, *refresh_end_ptr = NULL;
 	int i, len, ret;
 
+	mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
+
 #ifdef CONFIG_FB
 	if (!mode_option)
 		mode_option = fb_mode_option;

drivers/gpu/drm/selftests/drm_cmdline_selftests.h

@@ -64,3 +64,4 @@ cmdline_test(drm_cmdline_test_bpp_extra_and_option)
 cmdline_test(drm_cmdline_test_extra_and_option)
 cmdline_test(drm_cmdline_test_freestanding_options)
 cmdline_test(drm_cmdline_test_freestanding_force_e_and_options)
+cmdline_test(drm_cmdline_test_panel_orientation)

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

@@ -1092,6 +1092,28 @@ static int drm_cmdline_test_freestanding_force_e_and_options(void *ignored)
 	return 0;
 }
 
+static int drm_cmdline_test_panel_orientation(void *ignored)
+{
+	struct drm_cmdline_mode mode = { };
+
+	FAIL_ON(!drm_mode_parse_command_line_for_connector("panel_orientation=upside_down",
+							   &no_connector,
+							   &mode));
+	FAIL_ON(mode.specified);
+	FAIL_ON(mode.refresh_specified);
+	FAIL_ON(mode.bpp_specified);
+
+	FAIL_ON(mode.panel_orientation != DRM_MODE_PANEL_ORIENTATION_BOTTOM_UP);
+
+	FAIL_ON(mode.rb);
+	FAIL_ON(mode.cvt);
+	FAIL_ON(mode.interlace);
+	FAIL_ON(mode.margins);
+	FAIL_ON(mode.force != DRM_FORCE_UNSPECIFIED);
+
+	return 0;
+}
+
 #include "drm_selftest.c"
 
 static int __init test_drm_cmdline_init(void)

include/drm/drm_connector.h

@@ -1069,6 +1069,14 @@ struct drm_cmdline_mode {
 	 */
 	unsigned int rotation_reflection;
 
+	/**
+	 * @panel_orientation:
+	 *
+	 * drm-connector "panel orientation" property override value,
+	 * DRM_MODE_PANEL_ORIENTATION_UNKNOWN if not set.
+	 */
+	enum drm_panel_orientation panel_orientation;
+
 	/**
 	 * @tv_margins: TV margins to apply to the mode.
 	 */