USB: make urb scatter-gather support more generic

The WHCI HCD will also support urbs with scatter-gather lists.  Add a
usb_bus field to indicated how many sg list elements are supported by
the HCD.  Use this to decide whether to pass the scatter-list to the HCD
or not.

Make the usb-storage driver use this new field.

Signed-off-by: David Vrabel <david.vrabel@csr.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c
index 01e43a13a6bf..1599d86154c4 100644
--- a/drivers/usb/storage/usb.c
+++ b/drivers/usb/storage/usb.c
@@ -843,6 +843,15 @@ static int usb_stor_scan_thread(void * __us)
         complete_and_exit(&us->scanning_done, 0);
 }
 
+static unsigned int usb_stor_sg_tablesize(struct usb_interface *intf)
+{
+        struct usb_device *usb_dev = interface_to_usbdev(intf);
+
+        if (usb_dev->bus->sg_tablesize) {
+                return usb_dev->bus->sg_tablesize;
+        }
+        return SG_ALL;
+}
 
 /* First part of general USB mass-storage probing */
 int usb_stor_probe1(struct us_data **pus,
@@ -871,6 +880,7 @@ int usb_stor_probe1(struct us_data **pus,
          * Allow 16-byte CDBs and thus > 2TB
          */
         host->max_cmd_len = 16;
+        host->sg_tablesize = usb_stor_sg_tablesize(intf);
         *pus = us = host_to_us(host);
         memset(us, 0, sizeof(struct us_data));
         mutex_init(&(us->dev_mutex));