[PATCH 4/4] libata: Limit ATAPI DMA to R/W commands only for TORiSAN DVD drives

[Albert Lee <albertcc@tw.ibm.com>]

patch 4/4:

  Limit ATAPI DMA to R/W commands only for TORiSAN DRD-N216 DVD-ROM drives
  (http://bugzilla.kernel.org/show_bug.cgi?id=6710)

Signed-off-by: Albert Lee <albertcc@tw.ibm.com>
---
I guess maybe other commands like READ_DVD_STRUCTURE and READ_CD also
work under ATAPI DMA, but not confirmed by Vlad yet. So, allow ATAPI DMA
only for Read/Write here for safty.

Patch against libata-dev tree, for your review, thanks.

diff -Nrup 03_max_sect/drivers/ata/libata-core.c 04_dma_rw_only/drivers/ata/libata-core.c
--- 03_max_sect/drivers/ata/libata-core.c	2007-03-31 14:11:33.000000000 +0800
+++ 04_dma_rw_only/drivers/ata/libata-core.c	2007-03-31 14:27:47.000000000 +0800
@@ -1787,6 +1787,10 @@ int ata_dev_configure(struct ata_device 
 	if (ata_device_blacklisted(dev) & ATA_HORKAGE_MAX_SEC_240)
 		dev->max_sectors = min(ATA_MAX_SECTORS_240, dev->max_sectors);
 
+	/* limit ATAPI DMA to R/W commands only */
+	if (ata_device_blacklisted(dev) & ATA_HORKAGE_DMA_RW_ONLY)
+		dev->horkage |= ATA_HORKAGE_DMA_RW_ONLY;
+
 	if (ap->ops->dev_config)
 		ap->ops->dev_config(ap, dev);
 
@@ -3356,7 +3360,8 @@ static const struct ata_blacklist_entry 
 	{ "SAMSUNG CD-ROM SN-124","N001",	ATA_HORKAGE_NODMA },
 
 	/* Weird ATAPI devices */
-	{ "TORiSAN DVD-ROM DRD-N216", NULL,	ATA_HORKAGE_MAX_SEC_240 },
+	{ "TORiSAN DVD-ROM DRD-N216", NULL,	ATA_HORKAGE_MAX_SEC_240 |
+						ATA_HORKAGE_DMA_RW_ONLY },
 
 	/* Devices we expect to fail diagnostics */
 
@@ -3676,6 +3681,26 @@ int ata_check_atapi_dma(struct ata_queue
 	struct ata_port *ap = qc->ap;
 	int rc = 0; /* Assume ATAPI DMA is OK by default */
 
+	/* some drives can only do ATAPI DMA on read/write */
+	if (unlikely(qc->dev->horkage & ATA_HORKAGE_DMA_RW_ONLY)) {
+		struct scsi_cmnd *cmd = qc->scsicmd;
+		u8 *scsicmd = cmd->cmnd;
+
+		switch (scsicmd[0]) {
+		case READ_10:
+		case WRITE_10:
+		case READ_12:
+		case WRITE_12:
+		case READ_6:
+		case WRITE_6:
+			/* atapi dma maybe ok */
+			break;
+		default:
+			/* turn off atapi dma */
+			return 1;
+		}
+	}
+
 	if (ap->ops->check_atapi_dma)
 		rc = ap->ops->check_atapi_dma(qc);
 
diff -Nrup 03_max_sect/include/linux/libata.h 04_dma_rw_only/include/linux/libata.h
--- 03_max_sect/include/linux/libata.h	2007-03-31 14:07:49.000000000 +0800
+++ 04_dma_rw_only/include/linux/libata.h	2007-03-31 14:08:31.000000000 +0800
@@ -312,6 +312,7 @@ enum {
 	ATA_HORKAGE_NODMA	= (1 << 1),	/* DMA problems */
 	ATA_HORKAGE_NONCQ	= (1 << 2),	/* Don't use NCQ */
 	ATA_HORKAGE_MAX_SEC_240	= (1 << 3),	/* Limit max sects below 256 */
+	ATA_HORKAGE_DMA_RW_ONLY	= (1 << 4),	/* ATAPI DMA for RW only */
 };
 
 enum hsm_task_states {