4 files changed, 31 insertions, 0 deletions

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 62679bc031fb..0b387c1a8b7e 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1824,6 +1824,20 @@ static int proc_release_port(struct dev_state *ps, void __user *arg)
         return usb_hub_release_port(ps->dev, portnum, ps);
 }
 
+static int proc_get_capabilities(struct dev_state *ps, void __user *arg)
+{
+        __u32 caps;
+
+        caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM;
+        if (!ps->dev->bus->no_stop_on_short)
+                caps |= USBDEVFS_CAP_BULK_CONTINUATION;
+
+        if (put_user(caps, (__u32 __user *)arg))
+                return -EFAULT;
+
+        return 0;
+}
+
 /*
  * NOTE:  All requests here that have interface numbers as parameters
  * are assuming that somehow the configuration has been prevented from
@@ -1994,6 +2008,9 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
                 snoop(&dev->dev, "%s: RELEASE_PORT\n", __func__);
                 ret = proc_release_port(ps, p);
                 break;
+        case USBDEVFS_GET_CAPABILITIES:
+                ret = proc_get_capabilities(ps, p);
+                break;
         }
         usb_unlock_device(dev);
         if (ret >= 0)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index a979cd0dbe0f..7648b2d4b268 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4450,6 +4450,8 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
 
         /* Accept arbitrarily long scatter-gather lists */
         hcd->self.sg_tablesize = ~0;
+        /* XHCI controllers don't stop the ep queue on short packets :| */
+        hcd->self.no_stop_on_short = 1;
 
         if (usb_hcd_is_primary_hcd(hcd)) {
                 xhci = kzalloc(sizeof(struct xhci_hcd), GFP_KERNEL);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index f717fbdaee8e..d4f9de1acd45 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -331,6 +331,11 @@ struct usb_bus {
         u8 otg_port;                    /* 0, or number of OTG/HNP port */
         unsigned is_b_host:1;           /* true during some HNP roleswitches */
         unsigned b_hnp_enable:1;        /* OTG: did A-Host enable HNP? */
+        unsigned no_stop_on_short:1;    /*
+                                         * Quirk: some controllers don't stop
+                                         * the ep queue on a short transfer
+                                         * with the URB_SHORT_NOT_OK flag set.
+                                         */
         unsigned sg_tablesize;          /* 0 or largest number of sg list entries */
 
         int devnum_next;                /* Next open device number in
diff --git a/include/linux/usbdevice_fs.h b/include/linux/usbdevice_fs.h
index 15591d2ea400..07b2ceaaad70 100644
--- a/include/linux/usbdevice_fs.h
+++ b/include/linux/usbdevice_fs.h
@@ -125,6 +125,11 @@ struct usbdevfs_hub_portinfo {
         char port [127];        /* e.g. port 3 connects to device 27 */
 };
 
+/* Device capability flags */
+#define USBDEVFS_CAP_ZERO_PACKET                0x01
+#define USBDEVFS_CAP_BULK_CONTINUATION          0x02
+#define USBDEVFS_CAP_NO_PACKET_SIZE_LIM         0x04
+
 #ifdef __KERNEL__
 #ifdef CONFIG_COMPAT
 #include <linux/compat.h>
@@ -204,4 +209,6 @@ struct usbdevfs_ioctl32 {
 #define USBDEVFS_CONNECT           _IO('U', 23)
 #define USBDEVFS_CLAIM_PORT        _IOR('U', 24, unsigned int)
 #define USBDEVFS_RELEASE_PORT      _IOR('U', 25, unsigned int)
+#define USBDEVFS_GET_CAPABILITIES  _IOR('U', 26, __u32)
+
 #endif /* _LINUX_USBDEVICE_FS_H */