usb: phy: introduce usb_phy device type with its own uevent handler

The USB charger type and status was already propagated to userspace
through kobject_uevent_env during charger notify work. Nevertheless the
uevent could be lost e.g. because it could be fired at an early kernel
boot stage, way before udev daemon or any other user-space app was able
to catch it. Registering uevent hook for introduced usb_phy_dev_type
will allow to query sysfs 'uevent' file to restore that information at
any time.

Reviewed-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Link: https://lore.kernel.org/r/20210531122222.453628-1-grzegorz.jaszczyk@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/phy/phy.c

@@ -42,6 +42,12 @@ static const char *const usb_chger_type[] = {
 	[ACA_TYPE]			= "USB_CHARGER_ACA_TYPE",
 };
 
+static const char *const usb_chger_state[] = {
+	[USB_CHARGER_DEFAULT]	= "USB_CHARGER_DEFAULT",
+	[USB_CHARGER_PRESENT]	= "USB_CHARGER_PRESENT",
+	[USB_CHARGER_ABSENT]	= "USB_CHARGER_ABSENT",
+};
+
 static struct usb_phy *__usb_find_phy(struct list_head *list,
 	enum usb_phy_type type)
 {
@@ -74,6 +80,18 @@ static struct usb_phy *__of_usb_find_phy(struct device_node *node)
 	return ERR_PTR(-EPROBE_DEFER);
 }
 
+static struct usb_phy *__device_to_usb_phy(struct device *dev)
+{
+	struct usb_phy *usb_phy;
+
+	list_for_each_entry(usb_phy, &phy_list, head) {
+		if (usb_phy->dev == dev)
+			break;
+	}
+
+	return usb_phy;
+}
+
 static void usb_phy_set_default_current(struct usb_phy *usb_phy)
 {
 	usb_phy->chg_cur.sdp_min = DEFAULT_SDP_CUR_MIN;
@@ -105,35 +123,49 @@ static void usb_phy_set_default_current(struct usb_phy *usb_phy)
 static void usb_phy_notify_charger_work(struct work_struct *work)
 {
 	struct usb_phy *usb_phy = container_of(work, struct usb_phy, chg_work);
-	char uchger_state[50] = { 0 };
-	char uchger_type[50] = { 0 };
-	char *envp[] = { uchger_state, uchger_type, NULL };
 	unsigned int min, max;
 
 	switch (usb_phy->chg_state) {
 	case USB_CHARGER_PRESENT:
 		usb_phy_get_charger_current(usb_phy, &min, &max);
 
 		atomic_notifier_call_chain(&usb_phy->notifier, max, usb_phy);
-		snprintf(uchger_state, ARRAY_SIZE(uchger_state),
-			 "USB_CHARGER_STATE=%s", "USB_CHARGER_PRESENT");
 		break;
 	case USB_CHARGER_ABSENT:
 		usb_phy_set_default_current(usb_phy);
 
 		atomic_notifier_call_chain(&usb_phy->notifier, 0, usb_phy);
-		snprintf(uchger_state, ARRAY_SIZE(uchger_state),
-			 "USB_CHARGER_STATE=%s", "USB_CHARGER_ABSENT");
 		break;
 	default:
 		dev_warn(usb_phy->dev, "Unknown USB charger state: %d\n",
 			 usb_phy->chg_state);
 		return;
 	}
 
+	kobject_uevent(&usb_phy->dev->kobj, KOBJ_CHANGE);
+}
+
+static int usb_phy_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct usb_phy *usb_phy;
+	char uchger_state[50] = { 0 };
+	char uchger_type[50] = { 0 };
+
+	usb_phy = __device_to_usb_phy(dev);
+
+	snprintf(uchger_state, ARRAY_SIZE(uchger_state),
+		 "USB_CHARGER_STATE=%s", usb_chger_state[usb_phy->chg_state]);
+
 	snprintf(uchger_type, ARRAY_SIZE(uchger_type),
 		 "USB_CHARGER_TYPE=%s", usb_chger_type[usb_phy->chg_type]);
-	kobject_uevent_env(&usb_phy->dev->kobj, KOBJ_CHANGE, envp);
+
+	if (add_uevent_var(env, uchger_state))
+		return -ENOMEM;
+
+	if (add_uevent_var(env, uchger_type))
+		return -ENOMEM;
+
+	return 0;
 }
 
 static void __usb_phy_get_charger_type(struct usb_phy *usb_phy)
@@ -661,6 +693,11 @@ int usb_add_phy(struct usb_phy *x, enum usb_phy_type type)
 }
 EXPORT_SYMBOL_GPL(usb_add_phy);
 
+static struct device_type usb_phy_dev_type = {
+	.name = "usb_phy",
+	.uevent = usb_phy_uevent,
+};
+
 /**
  * usb_add_phy_dev - declare the USB PHY
  * @x: the USB phy to be used; or NULL
@@ -684,6 +721,8 @@ int usb_add_phy_dev(struct usb_phy *x)
 	if (ret)
 		return ret;
 
+	x->dev->type = &usb_phy_dev_type;
+
 	ATOMIC_INIT_NOTIFIER_HEAD(&x->notifier);
 
 	spin_lock_irqsave(&phy_lock, flags);