libata-core: Document some limits/assumptions about ID_ATA

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 75ccf46972d8c6089cee90646d9b3488e1738dad..d2141a04fff1f3da7e345e6d3541b406971feb1b 100644 (file)
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -1618,6 +1618,9 @@ static u32 ata_pio_mask_no_iordy(const struct ata_device *adev)
  *     devices.  This function also issues ATA_CMD_INIT_DEV_PARAMS
  *     for pre-ATA4 drives.
  *
+ *     FIXME: ATA_CMD_ID_ATA is optional for early drives and right
+ *     now we abort if we hit that case. 
+ *
  *     LOCKING:
  *     Kernel thread context (may sleep)
  *
@@ -1745,10 +1748,13 @@ int ata_dev_read_id(struct ata_device *dev, unsigned int *p_class,
                /*
                 * The exact sequence expected by certain pre-ATA4 drives is:
                 * SRST RESET
-                * IDENTIFY
-                * INITIALIZE DEVICE PARAMETERS
+                * IDENTIFY (optional in early ATA)
+                * INITIALIZE DEVICE PARAMETERS (later IDE and ATA)
                 * anything else..
                 * Some drives were very specific about that exact sequence.
+                *
+                * Note that ATA4 says lba is mandatory so the second check
+                * shoud never trigger.
                 */
                if (ata_id_major_version(id) < 4 || !ata_id_has_lba(id)) {
                        err_mask = ata_dev_init_params(dev, id[3], id[6]);