patch for skip "no device bus reset operations"

Signed-off-by: Joe Jin <lkmaillist@gmail.com>
---

--- linux-2.6.18.orig/drivers/scsi/libata-core.c	2006-09-29 16:58:38.000000000 +0800
+++ linux-2.6.18.new/drivers/scsi/libata-core.c	2006-09-29 16:53:20.000000000 +0800
@@ -2631,8 +2631,20 @@
 {
 	struct ata_eh_context *ehc = &ap->eh_context;
 	const unsigned long *timing = sata_ehc_deb_timing(ehc);
+	unsigned int slave_possible = ap->flags & ATA_FLAG_SLAVE_POSS;
+	unsigned int devmask = 0;
 	int rc;
 
+	if (ata_port_offline(ap)) {
+		return 0;
+	}
+
+	/* determine if device 0/1 are present */
+	if (ata_devchk(ap, 0))
+		devmask |= (1 << 0);
+	if (slave_possible && ata_devchk(ap, 1))
+		devmask |= (1 << 1);
+
 	/* handle link resume & hotplug spinup */
 	if ((ehc->i.flags & ATA_EHI_RESUME_LINK) &&
 	    (ap->flags & ATA_FLAG_HRST_TO_RESUME))
@@ -2660,7 +2672,8 @@
 	/* Wait for !BSY if the controller can wait for the first D2H
 	 * Reg FIS and we don't know that no device is attached.
 	 */
-	if (!(ap->flags & ATA_FLAG_SKIP_D2H_BSY) && !ata_port_offline(ap))
+	if (!(ap->flags & ATA_FLAG_SKIP_D2H_BSY) && 
+            !ata_port_offline(ap) && devmask)
 		ata_busy_sleep(ap, ATA_TMOUT_BOOT_QUICK, ATA_TMOUT_BOOT);
 
 	return 0;
@@ -2697,6 +2710,10 @@
 		devmask |= (1 << 0);
 	if (slave_possible && ata_devchk(ap, 1))
 		devmask |= (1 << 1);
+	
+	/* have not a invalid device been found */
+	if (!devmask)
+		return 0;
 
 	/* select device 0 again */
 	ap->ops->dev_select(ap, 0);