fine-grained PI control

[Anuj Gupta]

>
>Another wrinkle is that SCSI does not have a way to directly specify
>which tags to check. You can check guard only, check app+ref only, or
>all three. But you can't just check the ref tag if that's what you want
>to do.

Hi Martin,

When the drive is formatted with type1 integrity and dix is supported,
the block layer would generate/verify the guard and reftag. For scsi,
apptag would also need to be generated/verified as reftag-check can't
be specified alone. But I am not not able to find (in SCSI code) where
exactly: 
1. this apptag is being generated
2. and getting added to the PI buffer and scsi command.

Can you please point to where/how it is handled.

Thank you,
Anuj Gupta