libata: implement dump_id force param

Add dump_id libata.force parameter.  If specified, libata dumps full
IDENTIFY data during device configuration.  This is to aid debugging.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Larry Baker <baker@usgs.gov>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

Documentation/kernel-parameters.txt

@@ -1252,6 +1252,8 @@ and is between 256 and 4096 characters. It is defined in the file
 			* nohrst, nosrst, norst: suppress hard, soft
                           and both resets.
 
+			* dump_id: dump IDENTIFY data.
+
 			If there are multiple matching configurations changing
 			the same attribute, the last one is used.
 

drivers/ata/libata-core.c

@@ -2126,6 +2126,14 @@ int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
 		goto err_out;
 	}
 
+	if (dev->horkage & ATA_HORKAGE_DUMP_ID) {
+		ata_dev_printk(dev, KERN_DEBUG, "dumping IDENTIFY data, "
+			       "class=%d may_fallback=%d tried_spinup=%d\n",
+			       class, may_fallback, tried_spinup);
+		print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET,
+			       16, 2, id, ATA_ID_WORDS * sizeof(*id), true);
+	}
+
 	/* Falling back doesn't make sense if ID data was read
 	 * successfully at least once.
 	 */
@@ -6377,6 +6385,7 @@ static int __init ata_parse_force_one(char **cur,
 		{ "3.0Gbps",	.spd_limit	= 2 },
 		{ "noncq",	.horkage_on	= ATA_HORKAGE_NONCQ },
 		{ "ncq",	.horkage_off	= ATA_HORKAGE_NONCQ },
+		{ "dump_id",	.horkage_on	= ATA_HORKAGE_DUMP_ID },
 		{ "pio0",	.xfer_mask	= 1 << (ATA_SHIFT_PIO + 0) },
 		{ "pio1",	.xfer_mask	= 1 << (ATA_SHIFT_PIO + 1) },
 		{ "pio2",	.xfer_mask	= 1 << (ATA_SHIFT_PIO + 2) },

include/linux/libata.h

@@ -386,6 +386,7 @@ enum {
 	ATA_HORKAGE_1_5_GBPS	= (1 << 13),	/* force 1.5 Gbps */
 	ATA_HORKAGE_NOSETXFER	= (1 << 14),	/* skip SETXFER, SATA only */
 	ATA_HORKAGE_BROKEN_FPDMA_AA	= (1 << 15),	/* skip AA */
+	ATA_HORKAGE_DUMP_ID	= (1 << 16),	/* dump IDENTIFY data */
 
 	 /* DMA mask for user DMA control: User visible values; DO NOT
 	    renumber */