libata: add a host flag to ignore detected ATA devices

Where devices are visible via more than one host we sometimes wish to
indicate that cirtain devices should be ignored on a specific host.  Add a
host flag indicating that this host wishes to ignore ATA specific devices.
Signed-off-by: NAndy Whitcroft <apw@canonical.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-core.c

@@ -1973,6 +1973,12 @@ int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
 	if (class == ATA_DEV_ATA) {
 		if (!ata_id_is_ata(id) && !ata_id_is_cfa(id))
 			goto err_out;
+		if (ap->host->flags & ATA_HOST_IGNORE_ATA &&
+							ata_id_is_ata(id)) {
+			ata_dev_dbg(dev,
+				"host indicates ignore ATA devices, ignored\n");
+			return -ENOENT;
+		}
 	} else {
 		if (ata_id_is_ata(id))
 			goto err_out;

include/linux/libata.h

@@ -247,6 +247,7 @@ enum {
 	ATA_HOST_SIMPLEX	= (1 << 0),	/* Host is simplex, one DMA channel per host only */
 	ATA_HOST_STARTED	= (1 << 1),	/* Host started */
 	ATA_HOST_PARALLEL_SCAN	= (1 << 2),	/* Ports on this host can be scanned in parallel */
+	ATA_HOST_IGNORE_ATA	= (1 << 3),	/* Ignore ATA devices on this host. */
 
 	/* bits 24:31 of host->flags are reserved for LLD specific flags */