ide: add ide_dma_prepare() helper

* Add ide_dma_prepare() helper.

* Convert ide_issue_pc() and do_rw_taskfile() to use it.

* Make ide_build_sglist() static.

There should be no functional changes caused by this patch.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide-atapi.c b/drivers/ide/ide-atapi.c
index 1481f71f..89d2339 100644
--- a/drivers/ide/ide-atapi.c
+++ b/drivers/ide/ide-atapi.c
@@ -638,7 +638,6 @@
 {
 	struct ide_atapi_pc *pc;
 	ide_hwif_t *hwif = drive->hwif;
-	const struct ide_dma_ops *dma_ops = hwif->dma_ops;
 	ide_expiry_t *expiry = NULL;
 	struct request *rq = hwif->rq;
 	unsigned int timeout;
@@ -652,12 +651,8 @@
 		expiry = ide_cd_expiry;
 		timeout = ATAPI_WAIT_PC;
 
-		if (drive->dma) {
-			if (ide_build_sglist(drive, cmd))
-				drive->dma = !dma_ops->dma_setup(drive, cmd);
-			else
-				drive->dma = 0;
-		}
+		if (drive->dma)
+			drive->dma = !ide_dma_prepare(drive, cmd);
 	} else {
 		pc = drive->pc;
 
@@ -675,13 +670,8 @@
 			ide_dma_off(drive);
 		}
 
-		if ((pc->flags & PC_FLAG_DMA_OK) &&
-		     (drive->dev_flags & IDE_DFLAG_USING_DMA)) {
-			if (ide_build_sglist(drive, cmd))
-				drive->dma = !dma_ops->dma_setup(drive, cmd);
-			else
-				drive->dma = 0;
-		}
+		if (pc->flags & PC_FLAG_DMA_OK)
+			drive->dma = !ide_dma_prepare(drive, cmd);
 
 		if (!drive->dma)
 			pc->flags &= ~PC_FLAG_DMA_OK;