usbdevfs: Use scatter-gather lists for large bulk transfers

When using urb->transfer_buffer we need to allocate physical contiguous buffers
for the entire transfer, which is pretty much guaranteed to fail with large
transfers.

Currently userspace works around this by breaking large transfers into multiple
urbs. For large bulk transfers this leads to all kind of complications.

This patch makes it possible for userspace to reliable submit large bulk
transfers to scatter-gather capable host controllers in one go, by using a
scatterlist to break the transfer up in managable chunks.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/usbdevice_fs.h b/include/linux/usbdevice_fs.h
index 07b2ceaaad70..3b74666be027 100644
--- a/include/linux/usbdevice_fs.h
+++ b/include/linux/usbdevice_fs.h
@@ -129,6 +129,7 @@ struct usbdevfs_hub_portinfo {
 #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
 
 #ifdef __KERNEL__
 #ifdef CONFIG_COMPAT