USB: usbfs: allow URBs to be reaped after disconnection

The usbfs API has a peculiar hole: Users are not allowed to reap their
URBs after the device has been disconnected.  There doesn't seem to be
any good reason for this; it is an ad-hoc inconsistency.

The patch allows users to issue the USBDEVFS_REAPURB and
USBDEVFS_REAPURBNDELAY ioctls (together with their 32-bit counterparts
on 64-bit systems) even after the device is gone.  If no URBs are
pending for a disconnected device then the ioctls will return -ENODEV
rather than -EAGAIN, because obviously no new URBs will ever be able
to complete.

The patch also adds a new capability flag for
USBDEVFS_GET_CAPABILITIES to indicate that the reap-after-disconnect
feature is supported.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Chris Dickens <christopher.a.dickens@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/uapi/linux/usbdevice_fs.h b/include/uapi/linux/usbdevice_fs.h
index abe5f4bd4d82..019ba1e0799a 100644
--- a/include/uapi/linux/usbdevice_fs.h
+++ b/include/uapi/linux/usbdevice_fs.h
@@ -128,11 +128,12 @@ struct usbdevfs_hub_portinfo {
         char port [127];        /* e.g. port 3 connects to device 27 */
 };
 
-/* Device capability flags */
+/* System and bus capability flags */
 #define USBDEVFS_CAP_ZERO_PACKET                0x01
 #define USBDEVFS_CAP_BULK_CONTINUATION          0x02
 #define USBDEVFS_CAP_NO_PACKET_SIZE_LIM         0x04
 #define USBDEVFS_CAP_BULK_SCATTER_GATHER        0x08
+#define USBDEVFS_CAP_REAP_AFTER_DISCONNECT      0x10
 
 /* USBDEVFS_DISCONNECT_CLAIM flags & struct */