libata: add ata_sg_is_last() helper, use it in several drivers

drivers/scsi/pdc_adma.c

@@ -293,14 +293,14 @@ static void adma_eng_timeout(struct ata_port *ap)
 
 static int adma_fill_sg(struct ata_queued_cmd *qc)
 {
-	struct scatterlist *sg = qc->sg;
+	struct scatterlist *sg;
 	struct ata_port *ap = qc->ap;
 	struct adma_port_priv *pp = ap->private_data;
 	u8  *buf = pp->pkt;
-	int nelem, i = (2 + buf[3]) * 8;
+	int i = (2 + buf[3]) * 8;
 	u8 pFLAGS = pORD | ((qc->tf.flags & ATA_TFLAG_WRITE) ? pDIRO : 0);
 
-	for (nelem = 0; nelem < qc->n_elem; nelem++,sg++) {
+	ata_for_each_sg(sg, qc) {
 		u32 addr;
 		u32 len;
 
@@ -312,7 +312,7 @@ static int adma_fill_sg(struct ata_queued_cmd *qc)
 		*(__le32 *)(buf + i) = cpu_to_le32(len);
 		i += 4;
 
-		if ((nelem + 1) == qc->n_elem)
+		if (ata_sg_is_last(sg, qc))
 			pFLAGS |= pEND;
 		buf[i++] = pFLAGS;
 		buf[i++] = qc->dev->dma_mode & 0xf;

drivers/scsi/sata_mv.c

@@ -785,22 +785,24 @@ static void mv_port_stop(struct ata_port *ap)
 static void mv_fill_sg(struct ata_queued_cmd *qc)
 {
 	struct mv_port_priv *pp = qc->ap->private_data;
-	unsigned int i;
+	unsigned int i = 0;
+	struct scatterlist *sg;
 
-	for (i = 0; i < qc->n_elem; i++) {
+	ata_for_each_sg(sg, qc) {
 		u32 sg_len;
 		dma_addr_t addr;
 
-		addr = sg_dma_address(&qc->sg[i]);
-		sg_len = sg_dma_len(&qc->sg[i]);
+		addr = sg_dma_address(sg);
+		sg_len = sg_dma_len(sg);
 
 		pp->sg_tbl[i].addr = cpu_to_le32(addr & 0xffffffff);
 		pp->sg_tbl[i].addr_hi = cpu_to_le32((addr >> 16) >> 16);
 		assert(0 == (sg_len & ~MV_DMA_BOUNDARY));
 		pp->sg_tbl[i].flags_size = cpu_to_le32(sg_len);
-	}
-	if (0 < qc->n_elem) {
-		pp->sg_tbl[qc->n_elem - 1].flags_size |= EPRD_FLAG_END_OF_TBL;
+		if (ata_sg_is_last(sg, qc))
+			pp->sg_tbl[i].flags_size |= cpu_to_le32(EPRD_FLAG_END_OF_TBL);
+
+		i++;
 	}
 }
 

drivers/scsi/sata_sil24.c

@@ -416,15 +416,20 @@ static void sil24_phy_reset(struct ata_port *ap)
 static inline void sil24_fill_sg(struct ata_queued_cmd *qc,
 				 struct sil24_cmd_block *cb)
 {
-	struct scatterlist *sg = qc->sg;
 	struct sil24_sge *sge = cb->sge;
-	unsigned i;
+	struct scatterlist *sg;
+	unsigned int idx = 0;
 
-	for (i = 0; i < qc->n_elem; i++, sg++, sge++) {
+	ata_for_each_sg(sg, qc) {
 		sge->addr = cpu_to_le64(sg_dma_address(sg));
 		sge->cnt = cpu_to_le32(sg_dma_len(sg));
-		sge->flags = 0;
-		sge->flags = i < qc->n_elem - 1 ? 0 : cpu_to_le32(SGE_TRM);
+		if (ata_sg_is_last(sg, qc))
+			sge->flags = cpu_to_le32(SGE_TRM);
+		else
+			sge->flags = 0;
+
+		sge++;
+		idx++;
 	}
 }
 

include/linux/libata.h

@@ -480,6 +480,18 @@ extern int pci_test_config_bits(struct pci_dev *pdev, struct pci_bits *bits);
 #endif /* CONFIG_PCI */
 
 
+static inline int
+ata_sg_is_last(struct scatterlist *sg, struct ata_queued_cmd *qc)
+{
+	if (sg == &qc->pad_sgent)
+		return 1;
+	if (qc->pad_len)
+		return 0;
+	if (((sg - qc->__sg) + 1) == qc->n_elem)
+		return 1;
+	return 0;
+}
+
 static inline struct scatterlist *
 ata_qc_next_sg(struct scatterlist *sg, struct ata_queued_cmd *qc)
 {