3 files changed, 43 insertions, 10 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index daac0427bfd5..fc235b02ff27 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1606,7 +1606,6 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
                 struct usb_interface *new_intf)
 {
         int num_intfs, i, j;
-        struct usb_interface_cache *intf_cache;
         struct usb_host_interface *alt = NULL;
         int ret = 0;
         struct usb_hcd *hcd;
@@ -1654,15 +1653,8 @@ int usb_hcd_check_bandwidth(struct usb_device *udev,
                         }
                 }
                 for (i = 0; i < num_intfs; ++i) {
-
-                        /* Dig the endpoints for alt setting 0 out of the
-                         * interface cache for this interface
-                         */
-                        intf_cache = new_config->intf_cache[i];
-                        for (j = 0; j < intf_cache->num_altsetting; j++) {
-                                if (intf_cache->altsetting[j].desc.bAlternateSetting == 0)
-                                        alt = &intf_cache->altsetting[j];
-                        }
+                        /* Set up endpoints for alternate interface setting 0 */
+                        alt = usb_find_alt_setting(new_config, i, 0);
                         if (!alt) {
                                 printk(KERN_DEBUG "Did not find alt setting 0 for intf %d\n", i);
                                 continue;
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index d1e9440799de..99e54586a545 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -64,6 +64,43 @@ MODULE_PARM_DESC(autosuspend, "default autosuspend delay");
 
 
 /**
+ * usb_find_alt_setting() - Given a configuration, find the alternate setting
+ * for the given interface.
+ * @config - the configuration to search (not necessarily the current config).
+ * @iface_num - interface number to search in
+ * @alt_num - alternate interface setting number to search for.
+ *
+ * Search the configuration's interface cache for the given alt setting.
+ */
+struct usb_host_interface *usb_find_alt_setting(
+                struct usb_host_config *config,
+                unsigned int iface_num,
+                unsigned int alt_num)
+{
+        struct usb_interface_cache *intf_cache = NULL;
+        int i;
+
+        for (i = 0; i < config->desc.bNumInterfaces; i++) {
+                if (config->intf_cache[i]->altsetting[0].desc.bInterfaceNumber
+                                == iface_num) {
+                        intf_cache = config->intf_cache[i];
+                        break;
+                }
+        }
+        if (!intf_cache)
+                return NULL;
+        for (i = 0; i < intf_cache->num_altsetting; i++)
+                if (intf_cache->altsetting[i].desc.bAlternateSetting == alt_num)
+                        return &intf_cache->altsetting[i];
+
+        printk(KERN_DEBUG "Did not find alt setting %u for intf %u, "
+                        "config %u\n", alt_num, iface_num,
+                        config->desc.bConfigurationValue);
+        return NULL;
+}
+EXPORT_SYMBOL_GPL(usb_find_alt_setting);
+
+/**
  * usb_ifnum_to_if - get the interface object with a given interface number
  * @dev: the device whose current configuration is considered
  * @ifnum: the desired interface
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 6af3581e1114..e101a2d04d75 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -619,6 +619,10 @@ extern struct usb_interface *usb_ifnum_to_if(const struct usb_device *dev,
                 unsigned ifnum);
 extern struct usb_host_interface *usb_altnum_to_altsetting(
                 const struct usb_interface *intf, unsigned int altnum);
+extern struct usb_host_interface *usb_find_alt_setting(
+                struct usb_host_config *config,
+                unsigned int iface_num,
+                unsigned int alt_num);
 
 
 /**