libata: Report zeroed read after TRIM and max discard size

Our current TRIM payload is a single sector that can accommodate 64 *
65535 blocks being unmapped.  Report this value in the Block Limits
Maximum Unmap LBA count field.

If a storage device supports TRIM and the DRAT and RZAT bits are set,
report TPRZ=1 in Read Capacity(16).

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/include/linux/ata.h b/include/linux/ata.h
index e2595e8..dfa2298 100644
--- a/include/linux/ata.h
+++ b/include/linux/ata.h
@@ -75,6 +75,7 @@
 	ATA_ID_EIDE_DMA_TIME	= 66,
 	ATA_ID_EIDE_PIO		= 67,
 	ATA_ID_EIDE_PIO_IORDY	= 68,
+	ATA_ID_ADDITIONAL_SUPP	= 69,
 	ATA_ID_QUEUE_DEPTH	= 75,
 	ATA_ID_MAJOR_VER	= 80,
 	ATA_ID_COMMAND_SET_1	= 82,
@@ -816,6 +817,16 @@
 	return 0;
 }
 
+static inline int ata_id_has_zero_after_trim(const u16 *id)
+{
+	/* DSM supported, deterministic read, and read zero after trim set */
+	if (ata_id_has_trim(id) &&
+	    (id[ATA_ID_ADDITIONAL_SUPP] & 0x4020) == 0x4020)
+		return 1;
+
+	return 0;
+}
+
 static inline int ata_id_current_chs_valid(const u16 *id)
 {
 	/* For ATA-1 devices, if the INITIALIZE DEVICE PARAMETERS command