USB: Allow autosuspend delay to equal 0

This patch (as867) adds an entry for the new power/autosuspend
attribute in Documentation/ABI/testing, and it changes the behavior of
the delay value.  Now a delay of 0 means to autosuspend as soon as
possible, and negative values will prevent autosuspend.

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

6 files changed, 29 insertions, 10 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
new file mode 100644
index 000000000000..00a84326325f
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -0,0 +1,15 @@
+What:           /sys/bus/usb/devices/.../power/autosuspend
+Date:           March 2007
+KernelVersion:  2.6.21
+Contact:        Alan Stern <stern@rowland.harvard.edu>
+Description:
+                Each USB device directory will contain a file named
+                power/autosuspend.  This file holds the time (in seconds)
+                the device must be idle before it will be autosuspended.
+                0 means the device will be autosuspended as soon as
+                possible.  Negative values will prevent the device from
+                being autosuspended at all, and writing a negative value
+                will resume the device if it is already suspended.
+
+                The autosuspend delay for newly-created devices is set to
+                the value of the usbcore.autosuspend module parameter.
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 12533a958c51..2017942e0966 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1792,7 +1792,7 @@ and is between 256 and 4096 characters. It is defined in the file
                         for newly-detected USB devices (default 2).  This
                         is the time required before an idle device will be
                         autosuspended.  Devices for which the delay is set
-                        to 0 won't be autosuspended at all.
+                        to a negative value won't be autosuspended at all.
 
         usbhid.mousepoll=
                         [USBHID] The interval which mice are to be polled at.
diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index abea48de8766..884179f1e163 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -970,7 +970,7 @@ static int autosuspend_check(struct usb_device *udev)
         udev->do_remote_wakeup = device_may_wakeup(&udev->dev);
         if (udev->pm_usage_cnt > 0)
                 return -EBUSY;
-        if (!udev->autosuspend_delay)
+        if (udev->autosuspend_delay < 0)
                 return -EPERM;
 
         if (udev->actconfig) {
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 311d5df80386..731001f7d2c1 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -165,7 +165,7 @@ 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);
+        return sprintf(buf, "%d\n", udev->autosuspend_delay / HZ);
 }
 
 static ssize_t
@@ -173,17 +173,21 @@ 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;
+        int value;
 
-        if (sscanf(buf, "%u", &value) != 1 || value >= INT_MAX/HZ)
+        if (sscanf(buf, "%d", &value) != 1 || value >= INT_MAX/HZ ||
+                        value <= - INT_MAX/HZ)
                 return -EINVAL;
         value *= HZ;
 
-        old = udev->autosuspend_delay;
         udev->autosuspend_delay = value;
-        if (value > 0 && old == 0)
+        if (value >= 0)
                 usb_try_autosuspend_device(udev);
-
+        else {
+                usb_lock_device(udev);
+                usb_external_resume_device(udev);
+                usb_unlock_device(udev);
+        }
         return count;
 }
 
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 138252e0a1cf..6f35dce8a95d 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -55,7 +55,7 @@ struct workqueue_struct *ksuspend_usb_wq;
 #ifdef  CONFIG_USB_SUSPEND
 static int usb_autosuspend_delay = 2;           /* Default delay value,
                                                  * in seconds */
-module_param_named(autosuspend, usb_autosuspend_delay, uint, 0644);
+module_param_named(autosuspend, usb_autosuspend_delay, int, 0644);
 MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
 
 #else
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 87dc75a6cee1..cc24d089faa0 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -394,7 +394,7 @@ struct usb_device {
         struct delayed_work autosuspend; /* for delayed autosuspends */
         struct mutex pm_mutex;          /* protects PM operations */
 
-        unsigned autosuspend_delay;     /* in jiffies */
+        int autosuspend_delay;          /* in jiffies */
 
         unsigned auto_pm:1;             /* autosuspend/resume in progress */
         unsigned do_remote_wakeup:1;    /* remote wakeup should be enabled */