I was looking for an answer in the same vein as the question posted by
Derek Lambert, but that said I can answer his.
What is happening is here:
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
Your drive is responding to a mode sense command page called
Informational Exceptions. The response from your drive is going to
dictate what happens next. So since you are getting SMART available
and enabled, you are inviting the next request from the smart tools
which is an ATA_PASSTHROUGH. You will typically see the opcode 0x85
which is the 16 byte SCSI version of the command that you are seeing
0xA1. If your drive can answer SMART is Available but Disabled you
will likely find that the kernel warnings will stop.