gpu/drm: Create panelRegDA sysfs to expose panel's reg

Since ALS sensor's Firmware needs to keep track the PWM duty cycle of
each panels' version, therefore the panels' register 0xDA will be used
to identify the PWM duty cycle programmed in each panels' version.
The new /sys/class/drm/card0-DSI1/panelRegDA sysfs will be created.

Change-Id: I8abc7f31067614ce410348757aa8f75392788fb8
Signed-off-by: daiss1 <daiss1@lenovo.com>
Reviewed-on: https://gerrit.mot.com/1514795
SLTApproved: Slta Waiver
SME-Granted: SME Approvals Granted
Tested-by: Jira Key
Reviewed-by: Guobin Zhang <zhanggb@motorola.com>
Submit-Approved: Jira Key
Reviewed-on: https://gerrit.mot.com/1583968
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>

drivers/gpu/drm/drm_sysfs.c

@@ -234,13 +234,14 @@ static ssize_t panelId_show(struct device *device,
 			char *buf)
 {
 	struct drm_connector *connector = to_drm_connector(device);
+	int written = 0;
 
 	mutex_lock(&connector->dev->mode_config.mutex);
-	snprintf(buf, PAGE_SIZE, "0x%016llx\n",
+	written = snprintf(buf, PAGE_SIZE, "0x%016llx\n",
 	connector->display_info.panel_id);
 	mutex_unlock(&connector->dev->mode_config.mutex);
 
-	return 20;
+	return written;
 }
 
 static ssize_t panelVer_show(struct device *device,
@@ -248,13 +249,14 @@ static ssize_t panelVer_show(struct device *device,
 			char *buf)
 {
 	struct drm_connector *connector = to_drm_connector(device);
+	int written = 0;
 
 	mutex_lock(&connector->dev->mode_config.mutex);
-	snprintf(buf, PAGE_SIZE, "0x%016llx\n",
+	written = snprintf(buf, PAGE_SIZE, "0x%016llx\n",
 	connector->display_info.panel_ver);
 	mutex_unlock(&connector->dev->mode_config.mutex);
 
-	return 20;
+	return written;
 }
 
 static ssize_t panelName_show(struct device *device,
@@ -262,14 +264,30 @@ static ssize_t panelName_show(struct device *device,
 			char *buf)
 {
 	struct drm_connector *connector = to_drm_connector(device);
+	int written = 0;
 
 	mutex_lock(&connector->dev->mode_config.mutex);
-	snprintf(buf, PAGE_SIZE, "%s\n", connector->display_info.panel_name);
+	written = snprintf(buf, PAGE_SIZE, "%s\n", connector->display_info.panel_name);
 	mutex_unlock(&connector->dev->mode_config.mutex);
 
-	return sizeof(connector->display_info.panel_name);
+	return written;
 }
 
+static ssize_t panelRegDA_show(struct device *device,
+			struct device_attribute *attr,
+			char *buf)
+{
+	struct drm_connector *connector = to_drm_connector(device);
+	int written = 0;
+
+	mutex_lock(&connector->dev->mode_config.mutex);
+	written = snprintf(buf, PAGE_SIZE, "0x%02x\n", connector->display_info.panel_regDA);
+	mutex_unlock(&connector->dev->mode_config.mutex);
+
+	return written;
+}
+
+
 static DEVICE_ATTR_RW(status);
 static DEVICE_ATTR_RO(enabled);
 static DEVICE_ATTR_RO(dpms);
@@ -277,6 +295,7 @@ static DEVICE_ATTR_RO(modes);
 static DEVICE_ATTR_RO(panelId);
 static DEVICE_ATTR_RO(panelVer);
 static DEVICE_ATTR_RO(panelName);
+static DEVICE_ATTR_RO(panelRegDA);
 
 
 static struct attribute *connector_dev_attrs[] = {
@@ -287,6 +306,7 @@ static struct attribute *connector_dev_attrs[] = {
 	&dev_attr_panelId.attr,
 	&dev_attr_panelVer.attr,
 	&dev_attr_panelName.attr,
+	&dev_attr_panelRegDA.attr,
 	NULL
 };
 

include/drm/drm_connector.h

@@ -270,6 +270,7 @@ struct drm_display_info {
 
 	u64 panel_id;
 	u64 panel_ver;
+	u32 panel_regDA;
 	char panel_name[DRM_DISPLAY_NAME_LEN];
 
 

include/drm/drm_modes.h

@@ -290,6 +290,7 @@ struct drm_display_mode {
 
 	u64 panel_id;
 	u64 panel_ver;
+	u32 panel_regDA;
 	char panel_name[DRM_MODE_DISPLAY_NAME_LEN];
 	/**
 	 * @flags: