USB: unconfigure devices which have config 0

Some USB devices do have a configuration 0, in contravention of the
USB spec.  Normally 0 is supposed to indicate that a device is
unconfigured.

While we can't change what the device is doing, we can change usbcore.
This patch (as852) allows usb_set_configuration() to accept a config
value of -1 as indicating that the device should be unconfigured.  The
request actually sent to the device will still contain 0 as the value.
But even if the device does have a configuration 0, dev->actconfig
will be set to NULL and dev->state will be set to USB_STATE_ADDRESS.

Without some sort of special-case handling like this, there is no way
to unconfigure these non-compliant devices.

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

4 files changed, 22 insertions, 8 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 2087766f9e88..274f14f1633e 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -857,11 +857,11 @@ static int proc_setintf(struct dev_state *ps, void __user *arg)
 
 static int proc_setconfig(struct dev_state *ps, void __user *arg)
 {
-        unsigned int u;
+        int u;
         int status = 0;
         struct usb_host_config *actconfig;
 
-        if (get_user(u, (unsigned int __user *)arg))
+        if (get_user(u, (int __user *)arg))
                 return -EFAULT;
 
         actconfig = ps->dev->actconfig;
diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
index b531a4fd30c2..9bbcb20e2d94 100644
--- a/drivers/usb/core/generic.c
+++ b/drivers/usb/core/generic.c
@@ -184,7 +184,7 @@ static void generic_disconnect(struct usb_device *udev)
         /* if this is only an unbind, not a physical disconnect, then
          * unconfigure the device */
         if (udev->actconfig)
-                usb_set_configuration(udev, 0);
+                usb_set_configuration(udev, -1);
 
         usb_remove_sysfs_dev_files(udev);
 }
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index 8aca3574c2b5..74edaea5665d 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1316,6 +1316,14 @@ static void release_interface(struct device *dev)
  * use this kind of configurability; many devices only have one
  * configuration.
  *
+ * @configuration is the value of the configuration to be installed.
+ * According to the USB spec (e.g. section 9.1.1.5), configuration values
+ * must be non-zero; a value of zero indicates that the device in
+ * unconfigured.  However some devices erroneously use 0 as one of their
+ * configuration values.  To help manage such devices, this routine will
+ * accept @configuration = -1 as indicating the device should be put in
+ * an unconfigured state.
+ *
  * USB device configurations may affect Linux interoperability,
  * power consumption and the functionality available.  For example,
  * the default configuration is limited to using 100mA of bus power,
@@ -1347,10 +1355,15 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
         struct usb_interface **new_interfaces = NULL;
         int n, nintf;
 
-        for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
-                if (dev->config[i].desc.bConfigurationValue == configuration) {
-                        cp = &dev->config[i];
-                        break;
+        if (configuration == -1)
+                configuration = 0;
+        else {
+                for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
+                        if (dev->config[i].desc.bConfigurationValue ==
+                                        configuration) {
+                                cp = &dev->config[i];
+                                break;
+                        }
                 }
         }
         if ((!cp && configuration != 0))
@@ -1359,6 +1372,7 @@ int usb_set_configuration(struct usb_device *dev, int configuration)
         /* The USB spec says configuration 0 means unconfigured.
          * But if a device includes a configuration numbered 0,
          * we will accept it as a correctly configured state.
+         * Use -1 if you really want to unconfigure the device.
          */
         if (cp && configuration == 0)
                 dev_warn(&dev->dev, "config 0 descriptor??\n");
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index 4eaa0ee8e72f..0edfbafd702c 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -63,7 +63,7 @@ set_bConfigurationValue(struct device *dev, struct device_attribute *attr,
         struct usb_device       *udev = to_usb_device(dev);
         int                     config, value;
 
-        if (sscanf(buf, "%u", &config) != 1 || config > 255)
+        if (sscanf(buf, "%d", &config) != 1 || config < -1 || config > 255)
                 return -EINVAL;
         usb_lock_device(udev);
         value = usb_set_configuration(udev, config);