[libata] split ATA_QCFLAG_SG into ATA_QCFLAG_{SG,SINGLE}

In part of the effort to remove SCSI specifics from the libata
internals, remove references to cmd->use_sg.  cmd->use_sg
becomes ATA_QCFLAG_SG, and !cmd->use_sg becomes ATA_QCFLAG_SINGLE.

Convenience constant ATA_QCFLAG_DMAMAP is created when the programmer
wishes to refer collectively to ATA_QCFLAG_{SG,SINGLE}.

drivers/scsi/libata-core.c

@@ -1750,26 +1750,24 @@ static void ata_dev_set_pio(struct ata_port *ap, unsigned int device)
 static void ata_sg_clean(struct ata_queued_cmd *qc)
 {
 	struct ata_port *ap = qc->ap;
-	struct scsi_cmnd *cmd = qc->scsicmd;
 	struct scatterlist *sg = qc->sg;
-	int dir = scsi_to_pci_dma_dir(cmd->sc_data_direction);
+	int dir = qc->pci_dma_dir;
 
-	assert(dir == SCSI_DATA_READ || dir == SCSI_DATA_WRITE);
-	assert(qc->flags & ATA_QCFLAG_SG);
+	assert(qc->flags & ATA_QCFLAG_DMAMAP);
 	assert(sg != NULL);
 
-	if (!cmd->use_sg)
+	if (qc->flags & ATA_QCFLAG_SINGLE)
 		assert(qc->n_elem == 1);
 
 	DPRINTK("unmapping %u sg elements\n", qc->n_elem);
 
-	if (cmd->use_sg)
+	if (qc->flags & ATA_QCFLAG_SG)
 		pci_unmap_sg(ap->host_set->pdev, sg, qc->n_elem, dir);
 	else
 		pci_unmap_single(ap->host_set->pdev, sg_dma_address(&sg[0]),
 				 sg_dma_len(&sg[0]), dir);
 
-	qc->flags &= ~ATA_QCFLAG_SG;
+	qc->flags &= ~ATA_QCFLAG_DMAMAP;
 	qc->sg = NULL;
 }
 
@@ -1830,7 +1828,7 @@ static void ata_fill_sg(struct ata_queued_cmd *qc)
  */
 void ata_qc_prep(struct ata_queued_cmd *qc)
 {
-	if (!(qc->flags & ATA_QCFLAG_SG))
+	if (!(qc->flags & ATA_QCFLAG_DMAMAP))
 		return;
 
 	ata_fill_sg(qc);
@@ -1851,7 +1849,7 @@ static int ata_sg_setup_one(struct ata_queued_cmd *qc)
 {
 	struct ata_port *ap = qc->ap;
 	struct scsi_cmnd *cmd = qc->scsicmd;
-	int dir = scsi_to_pci_dma_dir(cmd->sc_data_direction);
+	int dir = qc->pci_dma_dir;
 	struct scatterlist *sg = qc->sg;
 	dma_addr_t dma_address;
 
@@ -1893,11 +1891,11 @@ static int ata_sg_setup(struct ata_queued_cmd *qc)
 	struct scatterlist *sg;
 	int n_elem, dir;
 
-	VPRINTK("ENTER, ata%u, use_sg %d\n", ap->id, cmd->use_sg);
-	assert(cmd->use_sg > 0);
+	VPRINTK("ENTER, ata%u\n", ap->id);
+	assert(qc->flags & ATA_QCFLAG_SG);
 
 	sg = (struct scatterlist *)cmd->request_buffer;
-	dir = scsi_to_pci_dma_dir(cmd->sc_data_direction);
+	dir = qc->pci_dma_dir;
 	n_elem = pci_map_sg(ap->host_set->pdev, sg, cmd->use_sg, dir);
 	if (n_elem < 1)
 		return -1;
@@ -2058,7 +2056,7 @@ static void ata_pio_sector(struct ata_port *ap)
 	qc->cursect++;
 	qc->cursg_ofs++;
 
-	if (cmd->use_sg)
+	if (qc->flags & ATA_QCFLAG_SG)
 		if ((qc->cursg_ofs * ATA_SECT_SIZE) == sg_dma_len(&sg[qc->cursg])) {
 			qc->cursg++;
 			qc->cursg_ofs = 0;
@@ -2299,7 +2297,7 @@ void ata_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
 	assert(qc != NULL);	/* ata_qc_from_tag _might_ return NULL */
 	assert(qc->flags & ATA_QCFLAG_ACTIVE);
 
-	if (likely(qc->flags & ATA_QCFLAG_SG))
+	if (likely(qc->flags & ATA_QCFLAG_DMAMAP))
 		ata_sg_clean(qc);
 
 	/* call completion callback */
@@ -2346,17 +2344,13 @@ void ata_qc_complete(struct ata_queued_cmd *qc, u8 drv_stat)
 int ata_qc_issue(struct ata_queued_cmd *qc)
 {
 	struct ata_port *ap = qc->ap;
-	struct scsi_cmnd *cmd = qc->scsicmd;
 
 	if (qc->flags & ATA_QCFLAG_SG) {
-		/* set up SG table */
-		if (cmd->use_sg) {
-			if (ata_sg_setup(qc))
-				goto err_out;
-		} else {
-			if (ata_sg_setup_one(qc))
-				goto err_out;
-		}
+		if (ata_sg_setup(qc))
+			goto err_out;
+	} else if (qc->flags & ATA_QCFLAG_SINGLE) {
+		if (ata_sg_setup_one(qc))
+			goto err_out;
 	}
 
 	ap->ops->qc_prep(qc);

drivers/scsi/libata-scsi.c

@@ -386,6 +386,7 @@ static void ata_scsi_translate(struct ata_port *ap, struct ata_device *dev,
 	if (!qc)
 		return;
 
+	/* data is present; dma-map it */
 	if (cmd->sc_data_direction == SCSI_DATA_READ ||
 	    cmd->sc_data_direction == SCSI_DATA_WRITE) {
 		if (unlikely(cmd->request_bufflen < 1)) {
@@ -394,7 +395,12 @@ static void ata_scsi_translate(struct ata_port *ap, struct ata_device *dev,
 			goto err_out;
 		}
 
-		qc->flags |= ATA_QCFLAG_SG; /* data is present; dma-map it */
+		if (cmd->use_sg)
+			qc->flags |= ATA_QCFLAG_SG;
+		else
+			qc->flags |= ATA_QCFLAG_SINGLE;
+
+		qc->pci_dma_dir = scsi_to_pci_dma_dir(cmd->sc_data_direction);
 	}
 
 	qc->complete_fn = ata_scsi_qc_complete;

drivers/scsi/sata_sx4.c

@@ -449,7 +449,7 @@ static void pdc20621_qc_prep(struct ata_queued_cmd *qc)
 	unsigned int i, last, idx, total_len = 0, sgt_len;
 	u32 *buf = (u32 *) &pp->dimm_buf[PDC_DIMM_HEADER_SZ];
 
-	if (!(qc->flags & ATA_QCFLAG_SG))
+	if (!(qc->flags & ATA_QCFLAG_DMAMAP))
 		return;
 
 	VPRINTK("ata%u: ENTER\n", ap->id);

include/linux/libata.h

@@ -112,7 +112,9 @@ enum {
 
 	ATA_QCFLAG_ACTIVE	= (1 << 1), /* cmd not yet ack'd to scsi lyer */
 	ATA_QCFLAG_DMA		= (1 << 2), /* data delivered via DMA */
-	ATA_QCFLAG_SG		= (1 << 4), /* have s/g table? */
+	ATA_QCFLAG_SG		= (1 << 3), /* have s/g table? */
+	ATA_QCFLAG_SINGLE	= (1 << 4), /* no s/g, just a single buffer */
+	ATA_QCFLAG_DMAMAP	= ATA_QCFLAG_SG | ATA_QCFLAG_SINGLE,
 
 	/* various lengths of time */
 	ATA_TMOUT_EDD		= 5 * HZ,	/* hueristic */
@@ -216,10 +218,14 @@ struct ata_queued_cmd {
 	unsigned long		flags;		/* ATA_QCFLAG_xxx */
 	unsigned int		tag;
 	unsigned int		n_elem;
+
+	int			pci_dma_dir;
+
 	unsigned int		nsect;
 	unsigned int		cursect;
 	unsigned int		cursg;
 	unsigned int		cursg_ofs;
+
 	struct ata_taskfile	tf;
 	struct scatterlist	sgent;