Re: [PATCH v6 09/19] scsi: allow enabling and disabling command duration limits

Damien Le Moal
2023-04-11T08:40:53Z

On 4/11/23 16:23, Christoph Hellwig wrote:
> On Tue, Apr 11, 2023 at 04:09:34PM +0900, Damien Le Moal wrote:
>> But yes, I guess we could just unconditionally enable CDL for ATA on device scan
>> to be on par with scsi, which has CDL always enabled.
>
> I'd prefer that. With a module option to not enable it just to be
> safe.

Thinking more about this, we cannot unconditionally enable CDL. The reason is
that CDL and NCQ priority are mutually exclusive: if CDL is enabled, NCQ
priority cannot be used. So with CDL unconditionally enabled, we cannot have NCQ
priority enabled, preventing the user from choosing its preferred IO latency
control method.