USB: export autosuspend delay in sysfs

This patch (as861) adds sysfs attributes to expose the autosuspend
delay value for each USB device.  If the user changes the delay from 0
(no autosuspend) to a positive value, an autosuspend is attempted.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 87 insertions, 1 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index a420d72a0254..9e3e943f313c 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1225,6 +1225,26 @@ void usb_autosuspend_device(struct usb_device *udev)
 }
 
 /**
+ * usb_try_autosuspend_device - attempt an autosuspend of a USB device and its interfaces
+ * @udev: the usb_device to autosuspend
+ *
+ * This routine should be called when a core subsystem thinks @udev may
+ * be ready to autosuspend.
+ *
+ * @udev's usage counter left unchanged.  If it or any of the usage counters
+ * for an active interface is greater than 0, or autosuspend is not allowed
+ * for any other reason, no autosuspend request will be queued.
+ *
+ * This routine can run only in process context.
+ */
+void usb_try_autosuspend_device(struct usb_device *udev)
+{
+        usb_autopm_do_device(udev, 0);
+        // dev_dbg(&udev->dev, "%s: cnt %d\n",
+        //              __FUNCTION__, udev->pm_usage_cnt);
+}
+
+/**
  * usb_autoresume_device - immediately autoresume a USB device and its interfaces
  * @udev: the usb_device to autoresume
  *
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index cad4fb323f6c..311d5df80386 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -158,6 +158,65 @@ show_quirks(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR(quirks, S_IRUGO, show_quirks, NULL);
 
+#ifdef  CONFIG_USB_SUSPEND
+
+static ssize_t
+show_autosuspend(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        struct usb_device *udev = to_usb_device(dev);
+
+        return sprintf(buf, "%u\n", udev->autosuspend_delay / HZ);
+}
+
+static ssize_t
+set_autosuspend(struct device *dev, struct device_attribute *attr,
+                const char *buf, size_t count)
+{
+        struct usb_device *udev = to_usb_device(dev);
+        unsigned value, old;
+
+        if (sscanf(buf, "%u", &value) != 1 || value >= INT_MAX/HZ)
+                return -EINVAL;
+        value *= HZ;
+
+        old = udev->autosuspend_delay;
+        udev->autosuspend_delay = value;
+        if (value > 0 && old == 0)
+                usb_try_autosuspend_device(udev);
+
+        return count;
+}
+
+static DEVICE_ATTR(autosuspend, S_IRUGO | S_IWUSR,
+                show_autosuspend, set_autosuspend);
+
+static char power_group[] = "power";
+
+static int add_power_attributes(struct device *dev)
+{
+        int rc = 0;
+
+        if (is_usb_device(dev))
+                rc = sysfs_add_file_to_group(&dev->kobj,
+                                &dev_attr_autosuspend.attr,
+                                power_group);
+        return rc;
+}
+
+static void remove_power_attributes(struct device *dev)
+{
+        sysfs_remove_file_from_group(&dev->kobj,
+                        &dev_attr_autosuspend.attr,
+                        power_group);
+}
+
+#else
+
+#define add_power_attributes(dev)       0
+#define remove_power_attributes(dev)    do {} while (0)
+
+#endif  /* CONFIG_USB_SUSPEND */
+
 /* Descriptor fields */
 #define usb_descriptor_attr_le16(field, format_string)                  \
 static ssize_t                                                          \
@@ -230,6 +289,10 @@ int usb_create_sysfs_dev_files(struct usb_device *udev)
         if (retval)
                 return retval;
 
+        retval = add_power_attributes(dev);
+        if (retval)
+                goto error;
+
         if (udev->manufacturer) {
                 retval = device_create_file(dev, &dev_attr_manufacturer);
                 if (retval)
@@ -262,6 +325,7 @@ void usb_remove_sysfs_dev_files(struct usb_device *udev)
         device_remove_file(dev, &dev_attr_manufacturer);
         device_remove_file(dev, &dev_attr_product);
         device_remove_file(dev, &dev_attr_serial);
+        remove_power_attributes(dev);
         sysfs_remove_group(&dev->kobj, &dev_attr_grp);
 }
 
diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
index b0a35f45b099..08b5a04e3755 100644
--- a/drivers/usb/core/usb.h
+++ b/drivers/usb/core/usb.h
@@ -66,11 +66,13 @@ static inline void usb_pm_unlock(struct usb_device *udev) {}
 #ifdef CONFIG_USB_SUSPEND
 
 extern void usb_autosuspend_device(struct usb_device *udev);
+extern void usb_try_autosuspend_device(struct usb_device *udev);
 extern int usb_autoresume_device(struct usb_device *udev);
 
 #else
 
-#define usb_autosuspend_device(udev)    do {} while (0)
+#define usb_autosuspend_device(udev)            do {} while (0)
+#define usb_try_autosuspend_device(udev)        do {} while (0)
 static inline int usb_autoresume_device(struct usb_device *udev)
 {
         return 0;