libata: make qc->nbytes include extra buffers

qc->nbytes didn't use to include extra buffers setup by libata core
layer and my be odd.  This patch makes qc->nbytes include any extra
buffers setup by libata core layer and guaranteed to be aligned on 4
byte boundary.

This value is to be used to program the host controller.  As this
represents the actual length of buffer available to the controller and
the controller must be able to deal with short transfers for ATAPI
commands which can transfer variable length, this shouldn't break any
controllers while making problems like rounding-down and controllers
choking up on odd transfer bytes much less likely.

The unmodified value is stored in new field qc->raw_nbytes.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 162f8b5509ac..7b7c78e42077 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -466,6 +466,7 @@ struct ata_queued_cmd {
         unsigned int            sect_size;
 
         unsigned int            nbytes;
+        unsigned int            raw_nbytes;
         unsigned int            curbytes;
 
         struct scatterlist      *cursg;
@@ -1362,7 +1363,7 @@ static inline void ata_qc_reinit(struct ata_queued_cmd *qc)
         qc->flags = 0;
         qc->cursg = NULL;
         qc->cursg_ofs = 0;
-        qc->nbytes = qc->curbytes = 0;
+        qc->nbytes = qc->raw_nbytes = qc->curbytes = 0;
         qc->n_elem = 0;
         qc->mapped_n_elem = 0;
         qc->n_iter = 0;