[PATCH v3 2/4] drm/edid: Add a function to check monitor string

[Hsin-Yi Wang <hsinyi@chromium.org>]

Add a function to check if the EDID base block contains a given string.

One of the use cases is fetching panel from a list of panel names, since
some panel vendors put the monitor name after EDID_DETAIL_MONITOR_STRING
instead of EDID_DETAIL_MONITOR_NAME.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
v2->v3: move string matching to drm_edid
---
 drivers/gpu/drm/drm_edid.c | 49 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_edid.h     |  1 +
 2 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 13454bc64ca2..fcdc2bd143dd 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2789,6 +2789,55 @@ u32 drm_edid_get_panel_id(struct edid_base_block *base_block)
 }
 EXPORT_SYMBOL(drm_edid_get_panel_id);
 
+/**
+ * drm_edid_has_monitor_string - Check if a EDID base block has certain string.
+ * @base_block: EDID base block to check.
+ * @str: pointer to a character array to hold the string to be checked.
+ *
+ * Check if the detailed timings section of a EDID base block has the given
+ * string.
+ *
+ * Return: True if the EDID base block contains the string, false otherwise.
+ */
+bool drm_edid_has_monitor_string(struct edid_base_block *base_block, const char *str)
+{
+	unsigned int i, j, k, buflen = strlen(str);
+
+	for (i = 0; i < EDID_DETAILED_TIMINGS; i++) {
+		struct detailed_timing *timing = &base_block->edid.detailed_timings[i];
+		unsigned int size = ARRAY_SIZE(timing->data.other_data.data.str.str);
+
+		if (buflen > size || timing->pixel_clock != 0 ||
+		    timing->data.other_data.pad1 != 0 ||
+		    (timing->data.other_data.type != EDID_DETAIL_MONITOR_NAME &&
+		     timing->data.other_data.type != EDID_DETAIL_MONITOR_STRING))
+			continue;
+
+		for (j = 0; j < buflen; j++) {
+			char c = timing->data.other_data.data.str.str[j];
+
+			if (c != str[j] ||  c == '\n')
+				break;
+		}
+
+		if (j == buflen) {
+			/* Allow trailing white spaces. */
+			for (k = j; k < size; k++) {
+				char c = timing->data.other_data.data.str.str[k];
+
+				if (c == '\n')
+					return true;
+				else if (c != ' ')
+					break;
+			}
+			if (k == size)
+				return true;
+		}
+	}
+
+	return false;
+}
+
 /**
  * drm_edid_get_base_block - Get a panel's EDID base block
  * @adapter: I2C adapter to use for DDC
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 2455d6ab2221..248ddb0a6b5d 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -416,6 +416,7 @@ struct edid *drm_get_edid(struct drm_connector *connector,
 			  struct i2c_adapter *adapter);
 struct edid_base_block *drm_edid_get_base_block(struct i2c_adapter *adapter);
 u32 drm_edid_get_panel_id(struct edid_base_block *base_block);
+bool drm_edid_has_monitor_string(struct edid_base_block *base_block, const char *str);
 struct edid *drm_get_edid_switcheroo(struct drm_connector *connector,
 				     struct i2c_adapter *adapter);
 struct edid *drm_edid_duplicate(const struct edid *edid);
-- 
2.44.0.rc1.240.g4c46232300-goog