USB: Export if an interface driver supports autosuspend.

Create a new sysfs file per interface named supports_autosuspend.  This
file returns true if an interface driver's .supports_autosuspend flag is
set.  It also returns true if the interface is unclaimed (since the USB
core will autosuspend a device if an interface is not claimed).

This new sysfs file will be useful for user space scripts to test whether
a USB device correctly auto-suspends.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 40 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 11a3c1682cec..df6c8a0159f1 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -85,3 +85,19 @@ Description:
 Users:
                 PowerTOP <power@bughost.org>
                 http://www.lesswatts.org/projects/powertop/
+
+What:           /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
+Date:           January 2008
+KernelVersion:  2.6.27
+Contact:        Sarah Sharp <sarah.a.sharp@intel.com>
+Description:
+                When read, this file returns 1 if the interface driver
+                for this interface supports autosuspend.  It also
+                returns 1 if no driver has claimed this interface, as an
+                unclaimed interface will not stop the device from being
+                autosuspended if all other interface drivers are idle.
+                The file returns 0 if autosuspend support has not been
+                added to the driver.
+Users:
+                USB PM tool
+                git://git.moblin.org/users/sarah/usb-pm-tool/
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 5e1f5d55bf04..f66fba11fbd5 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -743,6 +743,29 @@ static ssize_t show_modalias(struct device *dev,
 }
 static DEVICE_ATTR(modalias, S_IRUGO, show_modalias, NULL);
 
+static ssize_t show_supports_autosuspend(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct usb_interface *intf;
+        struct usb_device *udev;
+        int ret;
+
+        intf = to_usb_interface(dev);
+        udev = interface_to_usbdev(intf);
+
+        usb_lock_device(udev);
+        /* Devices will be autosuspended even when an interface isn't claimed */
+        if (!intf->dev.driver ||
+                        to_usb_driver(intf->dev.driver)->supports_autosuspend)
+                ret = sprintf(buf, "%u\n", 1);
+        else
+                ret = sprintf(buf, "%u\n", 0);
+        usb_unlock_device(udev);
+
+        return ret;
+}
+static DEVICE_ATTR(supports_autosuspend, S_IRUGO, show_supports_autosuspend, NULL);
+
 static struct attribute *intf_attrs[] = {
         &dev_attr_bInterfaceNumber.attr,
         &dev_attr_bAlternateSetting.attr,
@@ -751,6 +774,7 @@ static struct attribute *intf_attrs[] = {
         &dev_attr_bInterfaceSubClass.attr,
         &dev_attr_bInterfaceProtocol.attr,
         &dev_attr_modalias.attr,
+        &dev_attr_supports_autosuspend.attr,
         NULL,
 };
 static struct attribute_group intf_attr_grp = {