usb: expose usb port's pm qos flags to user space

This patch is to expose usb port's pm qos flags(pm_qos_no_power_off,
pm_qos_remote_wakeup) to user space. User can set pm_qos_no_power_off
flag to prohibit the port from being powered off.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 280433d80887..9a15b26944ec 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -67,6 +67,7 @@ static void usb_port_device_release(struct device *dev)
 {
         struct usb_port *port_dev = to_usb_port(dev);
 
+        dev_pm_qos_hide_flags(dev);
         usb_acpi_unregister_power_resources(dev);
         kfree(port_dev);
 }
@@ -176,7 +177,15 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
                 goto error_register;
 
         pm_runtime_set_active(&port_dev->dev);
-        pm_runtime_enable(&port_dev->dev);
+
+        /* It would be dangerous if user space couldn't
+         * prevent usb device from being powered off. So don't
+         * enable port runtime pm if failed to expose port's pm qos.
+         */
+        if (!dev_pm_qos_expose_flags(&port_dev->dev,
+                        PM_QOS_FLAG_NO_POWER_OFF))
+                pm_runtime_enable(&port_dev->dev);
+
 
         retval = usb_acpi_register_power_resources(&port_dev->dev);
         if (retval && retval != -ENODEV)