drm/connector: Add a function to lookup a TV mode by its name

As part of the command line parsing rework coming in the next patches,
we'll need to lookup drm_connector_tv_mode values by their name, already
defined in drm_tv_mode_enum_list.

In order to avoid any code duplication, let's do a function that will
perform a lookup of a TV mode name and return its value.

Reviewed-by: Noralf Trønnes <[e-mail]>
Tested-by: Mateusz Kwiatkowski <[e-mail]>
Acked-in-principle-or-something-like-that-by: Daniel Vetter <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>

drivers/gpu/drm/drm_connector.c

···
 };
 DRM_ENUM_NAME_FN(drm_get_tv_mode_name, drm_tv_mode_enum_list)
 
+/**
+ * drm_get_tv_mode_from_name - Translates a TV mode name into its enum value
+ * @name: TV Mode name we want to convert
+ * @len: Length of @name
+ *
+ * Translates @name into an enum drm_connector_tv_mode.
+ *
+ * Returns: the enum value on success, a negative errno otherwise.
+ */
+int drm_get_tv_mode_from_name(const char *name, size_t len)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(drm_tv_mode_enum_list); i++) {
+		const struct drm_prop_enum_list *item = &drm_tv_mode_enum_list[i];
+
+		if (strlen(item->name) == len && !strncmp(item->name, name, len))
+			return item->type;
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(drm_get_tv_mode_from_name);
+
 static const struct drm_prop_enum_list drm_tv_select_enum_list[] = {
 	{ DRM_MODE_SUBCONNECTOR_Automatic, "Automatic" }, /* DVI-I and TV-out */
 	{ DRM_MODE_SUBCONNECTOR_Composite, "Composite" }, /* TV-out */

drivers/gpu/drm/tests/Makefile

···
 obj-$(CONFIG_DRM_KUNIT_TEST) += \
 	drm_buddy_test.o \
 	drm_cmdline_parser_test.o \
+	drm_connector_test.o \
 	drm_damage_helper_test.o \
 	drm_dp_mst_helper_test.o \
 	drm_format_helper_test.o \

drivers/gpu/drm/tests/drm_connector_test.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Kunit test for drm_modes functions
+ */
+
+#include <drm/drm_connector.h>
+
+#include <kunit/test.h>
+
+struct drm_get_tv_mode_from_name_test {
+	const char *name;
+	enum drm_connector_tv_mode expected_mode;
+};
+
+#define TV_MODE_NAME(_name, _mode)		\
+	{					\
+		.name = _name,			\
+		.expected_mode = _mode,		\
+	}
+
+static void drm_test_get_tv_mode_from_name_valid(struct kunit *test)
+{
+	const struct drm_get_tv_mode_from_name_test *params = test->param_value;
+
+	KUNIT_EXPECT_EQ(test,
+			drm_get_tv_mode_from_name(params->name, strlen(params->name)),
+			params->expected_mode);
+}
+
+static const
+struct drm_get_tv_mode_from_name_test drm_get_tv_mode_from_name_valid_tests[] = {
+	TV_MODE_NAME("NTSC", DRM_MODE_TV_MODE_NTSC),
+	TV_MODE_NAME("NTSC-443", DRM_MODE_TV_MODE_NTSC_443),
+	TV_MODE_NAME("NTSC-J", DRM_MODE_TV_MODE_NTSC_J),
+	TV_MODE_NAME("PAL", DRM_MODE_TV_MODE_PAL),
+	TV_MODE_NAME("PAL-M", DRM_MODE_TV_MODE_PAL_M),
+	TV_MODE_NAME("PAL-N", DRM_MODE_TV_MODE_PAL_N),
+	TV_MODE_NAME("SECAM", DRM_MODE_TV_MODE_SECAM),
+};
+
+static void
+drm_get_tv_mode_from_name_valid_desc(const struct drm_get_tv_mode_from_name_test *t,
+				     char *desc)
+{
+	sprintf(desc, "%s", t->name);
+}
+
+KUNIT_ARRAY_PARAM(drm_get_tv_mode_from_name_valid,
+		  drm_get_tv_mode_from_name_valid_tests,
+		  drm_get_tv_mode_from_name_valid_desc);
+
+static void drm_test_get_tv_mode_from_name_truncated(struct kunit *test)
+{
+	const char *name = "NTS";
+	int ret;
+
+	ret = drm_get_tv_mode_from_name(name, strlen(name));
+	KUNIT_EXPECT_LT(test, ret, 0);
+};
+
+static struct kunit_case drm_get_tv_mode_from_name_tests[] = {
+	KUNIT_CASE_PARAM(drm_test_get_tv_mode_from_name_valid,
+			 drm_get_tv_mode_from_name_valid_gen_params),
+	KUNIT_CASE(drm_test_get_tv_mode_from_name_truncated),
+	{ }
+};
+
+static struct kunit_suite drm_get_tv_mode_from_name_test_suite = {
+	.name = "drm_get_tv_mode_from_name",
+	.test_cases = drm_get_tv_mode_from_name_tests,
+};
+
+kunit_test_suite(drm_get_tv_mode_from_name_test_suite);
+
+MODULE_AUTHOR("Maxime Ripard <[e-mail]>");
+MODULE_LICENSE("GPL");

include/drm/drm_connector.h

···
 const char *drm_get_content_protection_name(int val);
 const char *drm_get_hdcp_content_type_name(int val);
 
+int drm_get_tv_mode_from_name(const char *name, size_t len);
+
 int drm_mode_create_dvi_i_properties(struct drm_device *dev);
 void drm_connector_attach_dp_subconnector_property(struct drm_connector *connector);