config/patches/kmods/ddcci-driver/global-control-device.patch

diff --git a/ddcci-backlight/ddcci-backlight.c b/ddcci-backlight/ddcci-backlight.c
index 7a98522..e518bfc 100644
--- a/ddcci-backlight/ddcci-backlight.c
+++ b/ddcci-backlight/ddcci-backlight.c
@@ -29,6 +29,12 @@
 #define DDCCI_MONITOR_BACKLIGHT	0x13
 #define DDCCI_MONITOR_BL_WHITE		0x6B
 
+#define DDCCI_BL_MUX_MAX_DEVICES 8
+
+static struct backlight_device *ddcci_bl_global_control = NULL;
+static struct backlight_device *ddcci_bl_mux_devices[DDCCI_BL_MUX_MAX_DEVICES] = {NULL};
+static int ddcci_bl_mux_device_count = 0;
+
 static bool convenience_symlink = true;
 
 struct ddcci_monitor_drv_data {
@@ -101,13 +107,21 @@ static int ddcci_backlight_update_status(struct backlight_device *bl)
 	struct ddcci_monitor_drv_data *drv_data = bl_get_data(bl);
 	int brightness = bl->props.brightness;
 	int ret;
+  int i;
 
-	if (bl->props.power != FB_BLANK_UNBLANK ||
-	    bl->props.state & BL_CORE_FBBLANK)
-		brightness = 0;
+	if (drv_data == NULL) {
+		for (i = 0; i < ddcci_bl_mux_device_count; ++i) {
+			ddcci_bl_mux_devices[i]->props.brightness = bl->props.brightness;
+			ddcci_backlight_update_status(ddcci_bl_mux_devices[i]);
+		}
+	} else {
+		if (bl->props.power != FB_BLANK_UNBLANK ||
+				bl->props.state & BL_CORE_FBBLANK)
+			brightness = 0;
 
-	ret = ddcci_monitor_writectrl(drv_data->device, drv_data->used_vcp,
-				      brightness);
+		ret = ddcci_monitor_writectrl(drv_data->device, drv_data->used_vcp,
+								brightness);
+	}
 	if (ret > 0)
 		ret = 0;
 	return ret;
@@ -119,6 +133,10 @@ static int ddcci_backlight_get_brightness(struct backlight_device *bl)
 	int ret;
 	struct ddcci_monitor_drv_data *drv_data = bl_get_data(bl);
 
+	if (drv_data == NULL) {
+		return bl->props.brightness;
+	}
+
 	ret = ddcci_monitor_readctrl(drv_data->device, drv_data->used_vcp,
 				     &value, &maxval);
 	if (ret < 0)
@@ -277,6 +295,7 @@ static int ddcci_monitor_probe(struct ddcci_device *dev,
 {
 	struct ddcci_monitor_drv_data *drv_data;
 	struct backlight_properties props;
+	struct backlight_properties cprops;
 	struct backlight_device *bl = NULL;
 	int ret = 0;
 	bool support_luminance, support_bl_white;
@@ -369,6 +388,27 @@ static int ddcci_monitor_probe(struct ddcci_device *dev,
 		ddcci_backlight_create_symlink(dev);
 	}
 
+	if (ddcci_bl_global_control == NULL) {
+		printk(KERN_INFO "ddcci-backlight: registering global controller with brightness=%d, max_brightness=%d\n",
+				brightness, max_brightness);
+		cprops.type = BACKLIGHT_RAW;
+		cprops.max_brightness = max_brightness;
+		cprops.brightness = brightness;
+		ddcci_bl_global_control = devm_backlight_device_register(&dev->dev, "0000-ddcci_backlight_global_control",
+							&dev->dev, NULL,
+							&ddcci_backlight_ops, &cprops);
+	};
+
+	if(ddcci_bl_mux_device_count < DDCCI_BL_MUX_MAX_DEVICES) {
+		dev_info(&dev->dev, "registering backlight device %s as mux slave #%d",
+				dev_name(&dev->dev), ddcci_bl_mux_device_count);
+		ddcci_bl_mux_devices[ddcci_bl_mux_device_count] = bl;
+		dev_info(&dev->dev, "registered mux slave #%d successfully", ddcci_bl_mux_device_count);
+		++ddcci_bl_mux_device_count;
+	} else {
+		dev_info(&dev->dev, "new backlight device added, but mux slave array is at max capacity. global control will not work for this device.");
+	}
+
 	goto end;
 err_free:
 	devm_kfree(&dev->dev, drv_data);
@@ -378,8 +418,27 @@ end:
 
 static int ddcci_monitor_remove(struct ddcci_device *dev)
 {
+	int i,j;
+
 	dev_dbg(&dev->dev, "removing device\n");
 	ddcci_backlight_remove_symlink(dev);
+
+	for (i = 0; i < ddcci_bl_mux_device_count; ++i) {                                                 
+		struct backlight_device *bl = ddcci_bl_mux_devices[i];                                          
+		printk(KERN_INFO "ddcci-backlight: scan for remove global device %d from control array\n", i);     
+		if (dev == (struct ddcci_device*) bl_get_data(bl)) {                                       
+			printk(KERN_INFO "ddcci-backlight: removing global device %d from control array\n", i);          
+			ddcci_bl_mux_devices[i] = NULL;                                                               
+			for (j = i+1; j < ddcci_bl_mux_device_count; ++j) {                                           
+				if(ddcci_bl_mux_devices[j] != NULL) {                                                       
+					printk(KERN_INFO "ddcci-backlight: adjusting global devices %d -> %d\n", j, j-1);            
+					ddcci_bl_mux_devices[j-1] = ddcci_bl_mux_devices[j];                                          
+				}                                                                                       
+			}                                                                                         
+			--ddcci_bl_mux_device_count;                                                                  
+		}                                                                                           
+	}                                                                                             
+	
 	return 0;
 }