USB: add power/level sysfs attribute

This patch (as874) adds another piece to the user-visible part of the
USB autosuspend interface.  The new power/level sysfs attribute allows
users to force the device on (with autosuspend off), force the device
to sleep (with autoresume off), or return to normal automatic operation.

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

3 files changed, 90 insertions, 8 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 884179f1e163..9b6a60fafddb 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -872,8 +872,10 @@ static int usb_resume_device(struct usb_device *udev)
 
 done:
         // dev_dbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
-        if (status == 0)
+        if (status == 0) {
+                udev->autoresume_disabled = 0;
                 udev->dev.power.power_state.event = PM_EVENT_ON;
+        }
         return status;
 }
 
@@ -970,7 +972,7 @@ 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 < 0)
+        if (udev->autosuspend_delay < 0 || udev->autosuspend_disabled)
                 return -EPERM;
 
         if (udev->actconfig) {
@@ -1116,6 +1118,8 @@ static int usb_resume_both(struct usb_device *udev)
         struct usb_interface    *intf;
         struct usb_device       *parent = udev->parent;
 
+        if (udev->auto_pm && udev->autoresume_disabled)
+                return -EPERM;
         cancel_delayed_work(&udev->autosuspend);
         if (udev->state == USB_STATE_NOTATTACHED)
                 return -ENODEV;
@@ -1486,9 +1490,14 @@ static int usb_suspend(struct device *dev, pm_message_t message)
 
 static int usb_resume(struct device *dev)
 {
+        struct usb_device       *udev;
+
         if (!is_usb_device(dev))        /* Ignore PM for interfaces */
                 return 0;
-        return usb_external_resume_device(to_usb_device(dev));
+        udev = to_usb_device(dev);
+        if (udev->autoresume_disabled)
+                return -EPERM;
+        return usb_external_resume_device(udev);
 }
 
 #else
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index f08ec85a6d64..739f520908aa 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -42,7 +42,7 @@ static void usb_autosuspend_quirk(struct usb_device *udev)
 {
 #ifdef  CONFIG_USB_SUSPEND
         /* disable autosuspend, but allow the user to re-enable it via sysfs */
-        udev->autosuspend_delay = 0;
+        udev->autosuspend_disabled = 1;
 #endif
 }
 
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 731001f7d2c1..2ea47a38aefa 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -11,6 +11,7 @@
 
 
 #include <linux/kernel.h>
+#include <linux/string.h>
 #include <linux/usb.h>
 #include "usb.h"
 
@@ -184,9 +185,8 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
         if (value >= 0)
                 usb_try_autosuspend_device(udev);
         else {
-                usb_lock_device(udev);
-                usb_external_resume_device(udev);
-                usb_unlock_device(udev);
+                if (usb_autoresume_device(udev) == 0)
+                        usb_autosuspend_device(udev);
         }
         return count;
 }
@@ -194,22 +194,95 @@ set_autosuspend(struct device *dev, struct device_attribute *attr,
 static DEVICE_ATTR(autosuspend, S_IRUGO | S_IWUSR,
                 show_autosuspend, set_autosuspend);
 
+static const char on_string[] = "on";
+static const char auto_string[] = "auto";
+static const char suspend_string[] = "suspend";
+
+static ssize_t
+show_level(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        struct usb_device *udev = to_usb_device(dev);
+        const char *p = auto_string;
+
+        if (udev->state == USB_STATE_SUSPENDED) {
+                if (udev->autoresume_disabled)
+                        p = suspend_string;
+        } else {
+                if (udev->autosuspend_disabled)
+                        p = on_string;
+        }
+        return sprintf(buf, "%s\n", p);
+}
+
+static ssize_t
+set_level(struct device *dev, struct device_attribute *attr,
+                const char *buf, size_t count)
+{
+        struct usb_device *udev = to_usb_device(dev);
+        int len = count;
+        char *cp;
+        int rc = 0;
+
+        cp = memchr(buf, '\n', count);
+        if (cp)
+                len = cp - buf;
+
+        usb_lock_device(udev);
+
+        /* Setting the flags without calling usb_pm_lock is a subject to
+         * races, but who cares...
+         */
+        if (len == sizeof on_string - 1 &&
+                        strncmp(buf, on_string, len) == 0) {
+                udev->autosuspend_disabled = 1;
+                udev->autoresume_disabled = 0;
+                rc = usb_external_resume_device(udev);
+
+        } else if (len == sizeof auto_string - 1 &&
+                        strncmp(buf, auto_string, len) == 0) {
+                udev->autosuspend_disabled = 0;
+                udev->autoresume_disabled = 0;
+                rc = usb_external_resume_device(udev);
+
+        } else if (len == sizeof suspend_string - 1 &&
+                        strncmp(buf, suspend_string, len) == 0) {
+                udev->autosuspend_disabled = 0;
+                udev->autoresume_disabled = 1;
+                rc = usb_external_suspend_device(udev, PMSG_SUSPEND);
+
+        } else
+                rc = -EINVAL;
+
+        usb_unlock_device(udev);
+        return (rc < 0 ? rc : count);
+}
+
+static DEVICE_ATTR(level, S_IRUGO | S_IWUSR, show_level, set_level);
+
 static char power_group[] = "power";
 
 static int add_power_attributes(struct device *dev)
 {
         int rc = 0;
 
-        if (is_usb_device(dev))
+        if (is_usb_device(dev)) {
                 rc = sysfs_add_file_to_group(&dev->kobj,
                                 &dev_attr_autosuspend.attr,
                                 power_group);
+                if (rc == 0)
+                        rc = sysfs_add_file_to_group(&dev->kobj,
+                                        &dev_attr_level.attr,
+                                        power_group);
+        }
         return rc;
 }
 
 static void remove_power_attributes(struct device *dev)
 {
         sysfs_remove_file_from_group(&dev->kobj,
+                        &dev_attr_level.attr,
+                        power_group);
+        sysfs_remove_file_from_group(&dev->kobj,
                         &dev_attr_autosuspend.attr,
                         power_group);
 }