[PATCH V5 07/16] usb: image: microtek: use sg helper to operate scatterlist

[Ming Lei]

Use the scatterlist iterators and remove direct indexing of the
scatterlist array.

This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.

Cc: Oliver Neukum <oli...@neukum.org>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: linux-...@vger.kernel.org
Reviewed-by: Bart Van Assche <bvanass...@acm.org>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/usb/image/microtek.c | 20 ++++++++------------
 drivers/usb/image/microtek.h |  2 +-
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/image/microtek.c b/drivers/usb/image/microtek.c
index 607be1f4fe27..0a57c2cc8e5a 100644
--- a/drivers/usb/image/microtek.c
+++ b/drivers/usb/image/microtek.c
@@ -488,7 +488,6 @@ static void mts_command_done( struct urb *transfer )
 
 static void mts_do_sg (struct urb* transfer)
 {
-       struct scatterlist * sg;
        int status = transfer->status;
        MTS_INT_INIT();
 
@@ -500,13 +499,12 @@ static void mts_do_sg (struct urb* transfer)
                mts_transfer_cleanup(transfer);
         }
 
-       sg = scsi_sglist(context->srb);
-       context->fragment++;
+       context->curr_sg = sg_next(context->curr_sg);
        mts_int_submit_urb(transfer,
                           context->data_pipe,
-                          sg_virt(&sg[context->fragment]),
-                          sg[context->fragment].length,
-                          context->fragment + 1 == scsi_sg_count(context->srb) 
?
+                          sg_virt(context->curr_sg),
+                          context->curr_sg->length,
+                          sg_is_last(context->curr_sg) ?
                           mts_data_done : mts_do_sg);
 }
 
@@ -526,22 +524,20 @@ static void
 mts_build_transfer_context(struct scsi_cmnd *srb, struct mts_desc* desc)
 {
        int pipe;
-       struct scatterlist * sg;
-       
+
        MTS_DEBUG_GOT_HERE();
 
        desc->context.instance = desc;
        desc->context.srb = srb;
-       desc->context.fragment = 0;
 
        if (!scsi_bufflen(srb)) {
                desc->context.data = NULL;
                desc->context.data_length = 0;
                return;
        } else {
-               sg = scsi_sglist(srb);
-               desc->context.data = sg_virt(&sg[0]);
-               desc->context.data_length = sg[0].length;
+               desc->context.curr_sg = scsi_sglist(srb);
+               desc->context.data = sg_virt(desc->context.curr_sg);
+               desc->context.data_length = desc->context.curr_sg->length;
        }
 
 
diff --git a/drivers/usb/image/microtek.h b/drivers/usb/image/microtek.h
index 66685e59241a..7bd5f4639c4a 100644
--- a/drivers/usb/image/microtek.h
+++ b/drivers/usb/image/microtek.h
@@ -21,7 +21,7 @@ struct mts_transfer_context
        void *data;
        unsigned data_length;
        int data_pipe;
-       int fragment;
+       struct scatterlist *curr_sg;
 
        u8 *scsi_status; /* status returned from ep_response after command 
completion */
 };
-- 
2.20.1

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