Add association between DRM panels and backlight where defined

drivers/gpu/drm/bridge/panel.c

@@ -14,6 +14,7 @@
 #include <drm/drm_panel.h>
 #include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
+#include <linux/backlight.h>
 
 struct panel_bridge {
 	struct drm_bridge bridge;
@@ -86,6 +87,9 @@ static int panel_bridge_attach(struct drm_bridge *bridge,
 	drm_connector_attach_encoder(&panel_bridge->connector,
 					  bridge->encoder);
 
+	backlight_set_display_name(panel_bridge->panel->backlight,
+				   panel_bridge->connector.name);
+
 	if (bridge->dev->registered) {
 		if (connector->funcs->reset)
 			connector->funcs->reset(connector);

drivers/regulator/rpi-panel-v2-regulator.c

@@ -87,6 +87,39 @@ static const struct backlight_ops rpi_panel_v2_bl = {
 	.update_status	= rpi_panel_v2_update_status,
 };
 
+static int rpi_panel_v2_i2c_read(struct i2c_client *client, u8 reg, unsigned int *buf)
+{
+	struct i2c_msg msgs[1];
+	u8 addr_buf[1] = { reg };
+	u8 data_buf[1] = { 0, };
+	int ret;
+
+	/* Write register address */
+	msgs[0].addr = client->addr;
+	msgs[0].flags = 0;
+	msgs[0].len = ARRAY_SIZE(addr_buf);
+	msgs[0].buf = addr_buf;
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs))
+		return -EIO;
+
+	usleep_range(5000, 10000);
+
+	/* Read data from register */
+	msgs[0].addr = client->addr;
+	msgs[0].flags = I2C_M_RD;
+	msgs[0].len = 1;
+	msgs[0].buf = data_buf;
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs))
+		return -EIO;
+
+	*buf = data_buf[0];
+	return 0;
+}
+
 /*
  * I2C driver interface functions
  */
@@ -104,6 +137,7 @@ static int rpi_panel_v2_i2c_probe(struct i2c_client *i2c)
 		return -ENOMEM;
 
 	mutex_init(&state->lock);
+	i2c_set_clientdata(i2c, state);
 
 	regmap = devm_regmap_init_i2c(i2c, &rpi_panel_regmap_config);
 	if (IS_ERR(regmap)) {
@@ -113,7 +147,7 @@ static int rpi_panel_v2_i2c_probe(struct i2c_client *i2c)
 		goto error;
 	}
 
-	ret = regmap_read(regmap, REG_ID, &data);
+	ret = rpi_panel_v2_i2c_read(i2c, REG_ID, &data);
 	if (ret < 0) {
 		dev_err(&i2c->dev, "Failed to read REG_ID reg: %d\n", ret);
 		goto error;
@@ -168,6 +202,21 @@ static int rpi_panel_v2_i2c_probe(struct i2c_client *i2c)
 	return ret;
 }
 
+static void rpi_panel_v2_i2c_remove(struct i2c_client *client)
+{
+	struct rpi_panel_v2_lcd *state = i2c_get_clientdata(client);
+
+	mutex_destroy(&state->lock);
+}
+
+static void rpi_panel_v2_i2c_shutdown(struct i2c_client *client)
+{
+	struct rpi_panel_v2_lcd *state = i2c_get_clientdata(client);
+
+	regmap_write(state->regmap, REG_PWM, 0);
+	regmap_write(state->regmap, REG_POWERON, 0);
+}
+
 static const struct of_device_id rpi_panel_v2_dt_ids[] = {
 	{ .compatible = "raspberrypi,v2-touchscreen-panel-regulator" },
 	{},
@@ -180,6 +229,8 @@ static struct i2c_driver rpi_panel_v2_regulator_driver = {
 		.of_match_table = of_match_ptr(rpi_panel_v2_dt_ids),
 	},
 	.probe = rpi_panel_v2_i2c_probe,
+	.remove	= rpi_panel_v2_i2c_remove,
+	.shutdown = rpi_panel_v2_i2c_shutdown,
 };
 
 module_i2c_driver(rpi_panel_v2_regulator_driver);

drivers/video/backlight/backlight.c

@@ -285,6 +285,15 @@ static ssize_t max_brightness_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(max_brightness);
 
+static ssize_t display_name_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%s\n", bd->props.display_name);
+}
+static DEVICE_ATTR_RO(display_name);
+
 static ssize_t actual_brightness_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -365,6 +374,7 @@ static struct attribute *bl_device_attrs[] = {
 	&dev_attr_max_brightness.attr,
 	&dev_attr_scale.attr,
 	&dev_attr_type.attr,
+	&dev_attr_display_name.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(bl_device);
@@ -662,6 +672,17 @@ static int of_parent_match(struct device *dev, const void *data)
 	return dev->parent && dev->parent->of_node == data;
 }
 
+int backlight_set_display_name(struct backlight_device *bd, const char *name)
+{
+	if (!bd)
+		return -EINVAL;
+
+	strscpy_pad(bd->props.display_name, name, sizeof(bd->props.display_name));
+
+	return 0;
+}
+EXPORT_SYMBOL(backlight_set_display_name);
+
 /**
  * of_find_backlight_by_node() - find backlight device by device-tree node
  * @node: device-tree node of the backlight device

include/linux/backlight.h

@@ -270,6 +270,13 @@ struct backlight_properties {
 	 * @scale: The type of the brightness scale.
 	 */
 	enum backlight_scale scale;
+
+#define BL_DISPLAY_NAME_LEN 32
+	/**
+	 * @display_name: Optional name that can be registered to associate a
+	 * backlight device with a display device.
+	 */
+	char display_name[BL_DISPLAY_NAME_LEN];
 };
 
 /**
@@ -478,12 +485,20 @@ of_find_backlight_by_node(struct device_node *node)
 
 #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
 struct backlight_device *devm_of_find_backlight(struct device *dev);
+int backlight_set_display_name(struct backlight_device *bd, const char *name);
 #else
 static inline struct backlight_device *
 devm_of_find_backlight(struct device *dev)
 {
 	return NULL;
 }
+
+static inline int backlight_set_display_name(struct backlight_device *bd,
+					     const char *name)
+{
+	return 0;
+}
+
 #endif
 
 #endif