Re: [PATCH 2/3] ata: libata-scsi: Improve CDL control

[Igor Pylypiv <ipylypiv@google.com>]

On Wed, Apr 16, 2025 at 05:42:37PM +0900, Damien Le Moal wrote:
> With ATA devices supporting the CDL feature, using CDL requires that the
> feature be enabled with a SET FEATURES command. This command is issued
> as the translated command for the MODE SELECT command issued by
> scsi_cdl_enable() when the user enables CDL through the device
> cdl_enable sysfs attribute.
> 
> Currently, ata_mselect_control_ata_feature() always translates a MODE
> SELECT command for the ATA features subpage of the control mode page to
> a SET FEATURES command to enable or disable CDL based on the cdl_ctrl
> field. However, there is no need to issue the SET FEATURES command if:
> 1) The MODE SELECT command requests disabling CDL and CDL is already
>    disabled.
> 2) The MODE SELECT command requests enabling CDL and CDL is already
>    enabled.
> 
> Fix ata_mselect_control_ata_feature() to issue the SET FEATURES command
> only when necessary. Since enabling CDL also implies a reset of the CDL
> statistics log page, avoiding useless CDL enable operations also avoids
> clearing the CDL statistics log.
> 
> Also add debug messages to clearly signal when CDL is being enabled or
> disabled using a SET FEATURES command.
> 
> Fixes: df60f9c64576 ("scsi: ata: libata: Add ATA feature control sub-page translation")
> Cc: stable@vger.kernel.org
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>

Reviewed-by: Igor Pylypiv <ipylypiv@google.com>