Re: [PATCH] scsi: core: Disabe CDL by default

[Damien Le Moal <dlemoal@kernel.org>]

On 6/7/24 00:48, Bart Van Assche wrote:
> On 6/5/24 23:46, Damien Le Moal wrote:
>> For scsi devices supporting the Command Duration Limits feature set, the
>> user can enable/disable this feature use through the sysfs device
>> attribute cdl_enable. This attribute modification triggers a call to
>> scsi_cdl_enable() to enable and disable the feature for ATA devices and
>> set the scsi device cdl_enable to the user provided bool value.
> 
> Do we really need to disable CDL by default? Has it been considered to
> enable CDL by default if the Command Duration Limit mode pages that have
> been defined in SPC-5 are supported?

We cannot do that as that would potentially break users of ATA NCQ priority. The
reason is that for ATA drives that support both NCQ priority and CDL, if CDL is
enabled, NCQ priority cannot be used. If we were to change CDL to be enabled by
default, NCQ priority users would need to disable it before enabling NCQ
priority. That can break existing setups.

And this has been like this since kernel 6.5, so I am not going to change this now.

-- 
Damien Le Moal
Western Digital Research