libata-scsi: Remove !use_sg code paths

     This is a minimal patch needed to remove use of !use_sg
     but it is not a complete clean up of the !use_sg paths.
     Libata-core still has the qc->flags & ATA_QCFLAG_SG
     and !qc->n_elem code paths. Perhaps an ata maintainer
     would have a go at it.

     - TODO: further cleanup of qc->flags & ATA_QCFLAG_SG
       and !qc->n_elem code paths in libata-core
     - TODO: Use scsi_dma_{map,unmap} where applicable.
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/ata/libata-scsi.c

@@ -450,13 +450,8 @@ static struct ata_queued_cmd *ata_scsi_qc_new(struct ata_device *dev,
 		qc->scsicmd = cmd;
 		qc->scsidone = done;
 
-		if (cmd->use_sg) {
-			qc->__sg = (struct scatterlist *) cmd->request_buffer;
-			qc->n_elem = cmd->use_sg;
-		} else if (cmd->request_bufflen) {
-			qc->__sg = &qc->sgent;
-			qc->n_elem = 1;
-		}
+		qc->__sg = (struct scatterlist *) cmd->request_buffer;
+		qc->n_elem = cmd->use_sg;
 	} else {
 		cmd->result = (DID_OK << 16) | (QUEUE_FULL << 1);
 		done(cmd);
@@ -1504,11 +1499,7 @@ static int ata_scsi_translate(struct ata_device *dev, struct scsi_cmnd *cmd,
 			goto err_did;
 		}
 
-		if (cmd->use_sg)
-			ata_sg_init(qc, cmd->request_buffer, cmd->use_sg);
-		else
-			ata_sg_init_one(qc, cmd->request_buffer,
-					cmd->request_bufflen);
+		ata_sg_init(qc, cmd->request_buffer, cmd->use_sg);
 
 		qc->dma_dir = cmd->sc_data_direction;
 	}
@@ -1562,15 +1553,14 @@ static unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
 	u8 *buf;
 	unsigned int buflen;
 
-	if (cmd->use_sg) {
-		struct scatterlist *sg;
+	struct scatterlist *sg = (struct scatterlist *) cmd->request_buffer;
 
-		sg = (struct scatterlist *) cmd->request_buffer;
+	if (sg) {
 		buf = kmap_atomic(sg->page, KM_IRQ0) + sg->offset;
 		buflen = sg->length;
 	} else {
-		buf = cmd->request_buffer;
-		buflen = cmd->request_bufflen;
+		buf = NULL;
+		buflen = 0;
 	}
 
 	*buf_out = buf;
@@ -1590,12 +1580,9 @@ static unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
 
 static inline void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, u8 *buf)
 {
-	if (cmd->use_sg) {
-		struct scatterlist *sg;
-
-		sg = (struct scatterlist *) cmd->request_buffer;
+	struct scatterlist *sg = (struct scatterlist *) cmd->request_buffer;
+	if (sg)
 		kunmap_atomic(buf - sg->offset, KM_IRQ0);
-	}
 }
 
 /**