ide: add ->dma_check method

* Add (an optional) ->dma_check method for checking if DMA can be
  used for a given command and fail DMA setup in ide_dma_prepare()
  if necessary.

* Convert alim15x3 and trm290 host drivers to use ->dma_check.

* Rename ali15x3_dma_setup() to ali_dma_check() while at it.

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>

drivers/ide/alim15x3.c

@@ -189,20 +189,20 @@ static void ali_set_dma_mode(ide_drive_t *drive, const u8 speed)
 }
 
 /**
- *	ali15x3_dma_setup	-	begin a DMA phase
+ *	ali_dma_check	-	DMA check
  *	@drive:	target device
  *	@cmd: command
  *
  *	Returns 1 if the DMA cannot be performed, zero on success.
  */
 
-static int ali15x3_dma_setup(ide_drive_t *drive, struct ide_cmd *cmd)
+static int ali_dma_check(ide_drive_t *drive, struct ide_cmd *cmd)
 {
 	if (m5229_revision < 0xC2 && drive->media != ide_disk) {
 		if (cmd->tf_flags & IDE_TFLAG_WRITE)
 			return 1;	/* try PIO instead of DMA */
 	}
-	return ide_dma_setup(drive, cmd);
+	return 0;
 }
 
 /**
@@ -503,11 +503,12 @@ static const struct ide_port_ops ali_port_ops = {
 
 static const struct ide_dma_ops ali_dma_ops = {
 	.dma_host_set		= ide_dma_host_set,
-	.dma_setup		= ali15x3_dma_setup,
+	.dma_setup		= ide_dma_setup,
 	.dma_start		= ide_dma_start,
 	.dma_end		= ide_dma_end,
 	.dma_test_irq		= ide_dma_test_irq,
 	.dma_lost_irq		= ide_dma_lost_irq,
+	.dma_check		= ali_dma_check,
 	.dma_timer_expiry	= ide_dma_sff_timer_expiry,
 	.dma_sff_read_status	= ide_dma_sff_read_status,
 };

drivers/ide/ide-dma.c

@@ -566,9 +566,12 @@ EXPORT_SYMBOL_GPL(ide_allocate_dma_engine);
 
 int ide_dma_prepare(ide_drive_t *drive, struct ide_cmd *cmd)
 {
+	const struct ide_dma_ops *dma_ops = drive->hwif->dma_ops;
+
 	if ((drive->dev_flags & IDE_DFLAG_USING_DMA) == 0 ||
+	    (dma_ops->dma_check && dma_ops->dma_check(drive, cmd)) ||
 	    ide_build_sglist(drive, cmd) == 0 ||
-	    drive->hwif->dma_ops->dma_setup(drive, cmd))
+	    dma_ops->dma_setup(drive, cmd))
 		return 1;
 	return 0;
 }

drivers/ide/trm290.c

@@ -176,19 +176,21 @@ static void trm290_selectproc (ide_drive_t *drive)
 	trm290_prepare_drive(drive, !!(drive->dev_flags & IDE_DFLAG_USING_DMA));
 }
 
-static int trm290_dma_setup(ide_drive_t *drive, struct ide_cmd *cmd)
+static int trm290_dma_check(ide_drive_t *drive, struct ide_cmd *cmd)
 {
-	ide_hwif_t *hwif = drive->hwif;
-	unsigned int count, rw;
-
 	if (cmd->tf_flags & IDE_TFLAG_WRITE) {
 #ifdef TRM290_NO_DMA_WRITES
 		/* always use PIO for writes */
 		return 1;
 #endif
-		rw = 1;
-	} else
-		rw = 2;
+	}
+	return 0;
+}
+
+static int trm290_dma_setup(ide_drive_t *drive, struct ide_cmd *cmd)
+{
+	ide_hwif_t *hwif = drive->hwif;
+	unsigned int count, rw = (cmd->tf_flags & IDE_TFLAG_WRITE) ? 1 : 2;
 
 	count = ide_build_dmatable(drive, cmd);
 	if (count == 0) {
@@ -312,6 +314,7 @@ static struct ide_dma_ops trm290_dma_ops = {
 	.dma_end		= trm290_dma_end,
 	.dma_test_irq		= trm290_dma_test_irq,
 	.dma_lost_irq		= ide_dma_lost_irq,
+	.dma_check		= trm290_dma_check,
 };
 
 static const struct ide_port_info trm290_chipset __devinitdata = {

include/linux/ide.h

@@ -717,6 +717,7 @@ struct ide_dma_ops {
 	int	(*dma_test_irq)(struct ide_drive_s *);
 	void	(*dma_lost_irq)(struct ide_drive_s *);
 	/* below ones are optional */
+	int	(*dma_check)(struct ide_drive_s *, struct ide_cmd *);
 	int	(*dma_timer_expiry)(struct ide_drive_s *);
 	void	(*dma_clear)(struct ide_drive_s *);
 	/*