[RFC PATCH 1/2] usb: usb port power off mechanism add "auto" option

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

This patch is to add "auto" option to attribute portX/control.
When echo "auto", the port's feature PORT_POWER would be clear
if the port's connect type was mark not-used(connectability and
visibility are both cleared) and with no device attached.

Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
---
 drivers/usb/core/hub.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b8a5af4..65c91300 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -42,6 +42,7 @@
 enum port_power_policy {
 	USB_PORT_POWER_ON = 0,
 	USB_PORT_POWER_OFF,
+	USB_PORT_POWER_AUTO,
 };
 
 struct usb_port {
@@ -105,6 +106,7 @@ struct device_type usb_port_device_type = {
 
 static const char on_string[] = "on";
 static const char off_string[] = "off";
+static const char auto_string[] = "auto";
 static const struct attribute_group *port_dev_group[];
 
 static inline int hub_is_superspeed(struct usb_device *hdev)
@@ -4703,6 +4705,9 @@ static ssize_t show_port_power_control(struct device *dev,
 	case USB_PORT_POWER_OFF:
 		result = off_string;
 		break;
+	case USB_PORT_POWER_AUTO:
+		result = auto_string;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -4741,6 +4746,18 @@ static ssize_t store_port_power_control(struct device *dev,
 		usb_autopm_put_interface(intf);
 		if (ret < 0)
 			return -EIO;
+	} else if (len == sizeof(auto_string) - 1
+			&& strncmp(buf, auto_string, len) == 0) {
+		hub_port->port_power_policy = USB_PORT_POWER_AUTO;
+		if (hub_port->connect_type
+			== USB_PORT_NOT_USED && !hub_port->child) {
+			usb_autopm_get_interface(intf);
+			ret = clear_port_feature(hdev, port1,
+				USB_PORT_FEAT_POWER);
+			usb_autopm_put_interface(intf);
+			if (ret < 0)
+				return -EIO;
+		}
 	} else
 		return -EINVAL;
 
-- 
1.7.9.5

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