usb: gadget: workaround storage command size issues

Try to workaround issues with bad SCSI implementations
by ignoring the command size error.

Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 17 insertions, 4 deletions

diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index 0c632d22a631..e0f616f39ba0 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -2676,11 +2676,24 @@ static int check_command(struct fsg_dev *fsg, int cmnd_size,
         /* Verify the length of the command itself */
         if (cmnd_size != fsg->cmnd_size) {
 
-                /* Special case workaround: MS-Windows issues REQUEST SENSE
-                 * with cbw->Length == 12 (it should be 6). */
-                if (fsg->cmnd[0] == SC_REQUEST_SENSE && fsg->cmnd_size == 12)
+                /* Special case workaround: There are plenty of buggy SCSI
+                 * implementations. Many have issues with cbw->Length
+                 * field passing a wrong command size. For those cases we
+                 * always try to work around the problem by using the length
+                 * sent by the host side provided it is at least as large
+                 * as the correct command length.
+                 * Examples of such cases would be MS-Windows, which issues
+                 * REQUEST SENSE with cbw->Length == 12 where it should
+                 * be 6, and xbox360 issuing INQUIRY, TEST UNIT READY and
+                 * REQUEST SENSE with cbw->Length == 10 where it should
+                 * be 6 as well.
+                 */
+                if (cmnd_size <= fsg->cmnd_size) {
+                        DBG(fsg, "%s is buggy! Expected length %d "
+                                        "but we got %d\n", name,
+                                        cmnd_size, fsg->cmnd_size);
                         cmnd_size = fsg->cmnd_size;
-                else {
+                } else {
                         fsg->phase_error = 1;
                         return -EINVAL;
                 }