Re: [PATCH 0/2] scsi: sd: use READ/WRITE/SYNC (16) commands per ZBC

[Damien Le Moal <damien.lemoal@opensource.wdc.com>]

On 11/10/22 17:19, hch@infradead.org wrote:
> On Thu, Nov 10, 2022 at 02:20:09AM +0000, Shinichiro Kawasaki wrote:
>> My point was to make the check strictly follow the ZBC spec. But now I see that
>> it's the better to keep enforcing 16 byte commands to host-aware devices. I will
>> drop the first patch and revise the second patch to enforce SYNC 16 on both
>> host-aware and host-managed devices.
> 
> We don't "enforce" anything.  We just don't send the legacy commands for
> devices that are guaranteed to be modern.  What is the advantage of
> ever sending 10 bytes commands (inluding SYNCHRONIZE CACHE) to a modern
> device?

The ZBC specs define SYNC 16 as optional while SYNC 10 is mandatory. So
the device may not support SYNC 16 and we would get an invalid opcode
error. For SYNC, no advantages between SYNC 10 and SYNC 16. Not even
sure why they both exist. The point here is making sure we use the one
that the drive MUST support. That is, SYNC 16 for host managed and SYNC
10 for host aware (but these likely all also support SYNC 16, but we
cannot be sure of it).

-- 
Damien Le Moal
Western Digital Research