docs: sysfs-block: Clarify integrity sysfs attributes

The /sys/block/<disk>/integrity fields are historically set
if T10 protection Information is enabled.

It is not set if some upper layer uses integrity metadata.
Document it.

Signed-off-by: Milan Broz <[email protected]>
Co-developed-by: Martin K. Petersen <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: mbroz

Documentation/ABI/stable/sysfs-block

@@ -109,6 +109,10 @@ Contact:	Martin K. Petersen <[email protected]>
 Description:
 		Indicates whether a storage device is capable of storing
 		integrity metadata. Set if the device is T10 PI-capable.
+		This flag is set to 1 if the storage media is formatted
+		with T10 Protection Information. If the storage media is
+		not formatted with T10 Protection Information, this flag
+		is set to 0.
 
 
 What:		/sys/block/<disk>/integrity/format
@@ -117,6 +121,13 @@ Contact:	Martin K. Petersen <[email protected]>
 Description:
 		Metadata format for integrity capable block device.
 		E.g. T10-DIF-TYPE1-CRC.
+		This field describes the type of T10 Protection Information
+		that the block device can send and receive.
+		If the device can store application integrity metadata but
+		no T10 Protection Information profile is used, this field
+		contains "nop".
+		If the device does not support integrity metadata, this
+		field contains "none".
 
 
 What:		/sys/block/<disk>/integrity/protection_interval_bytes
@@ -142,7 +153,17 @@ Date:		June 2008
 Contact:	Martin K. Petersen <[email protected]>
 Description:
 		Number of bytes of integrity tag space available per
-		512 bytes of data.
+		protection_interval_bytes, which is typically
+		the device's logical block size.
+		This field describes the size of the application tag
+		if the storage device is formatted with T10 Protection
+		Information and permits use of the application tag.
+		The tag_size is reported in bytes and indicates the
+		space available for adding an opaque tag to each block
+		(protection_interval_bytes).
+		If the device does not support T10 Protection Information
+		(even if the device provides application integrity
+		metadata space), this field is set to 0.
 
 
 What:		/sys/block/<disk>/integrity/write_generate