Re: [PATCH v2] ata: libata-scsi: Fix get identity data failed

John Garry
2023-05-22T11:29:00Z

On 22/05/2023 09:00, Jason Yan wrote:
>
> OK, so the issue is that __ata_scsi_find_dev() calls ata_find_dev() with
> devno
> == scsidev->id. This leads to devno being 0, 1, 2 and 3 for connected
> drives

This numbering comes from sas_rphy_add():
...
if (identify->device_type == SAS_END_DEVICE &&
(identify->target_port_protocols &
(SAS_PROTOCOL_SSP | SAS_PROTOCOL_STP | SAS_PROTOCOL_SATA)))
rphy->scsi_target_id = sas_host->next_target_id++;

..

scsi_scan_target(&rphy->dev, 0, rphy->scsi_target_id, lun,
SCSI_SCAN_INITIAL);
}

So libata and scsi_transport_sas just use different sdev id numbering
schemes for host scan.

> sdd, sd1, sdf and sdg, as shown by lsscsi. However, each drive has its own
> port+link, with the link for each one having  ata_link_max_devices() ==
> 1, so
> ata_find_dev() works only for the first drive with scsidev->id == 0 and
> fails
> for the others. A naive fix would be this:
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 7bb12deab70c..e4d6f17d7ccc 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -2718,7 +2718,7 @@ static struct ata_device *__ata_scsi_find_dev(struct
> ata_port *ap,
>          if (!sata_pmp_attached(ap)) {
>                  if (unlikely(scsidev->channel || scsidev->lun))
>                          return NULL;
> -               devno = scsidev->id;
> +               devno = 0;
Would this pattern work:

ata_for_each_dev(ata_dev, link, ALL) {
if (ata_dev->sdev == sdev)
return ata_dev;
}

If not, I think it's ok to have devno = 0 assignment under SAS_HOST
flag, even though it's far from ideal. Not both of these are not
preferred, then, as I mentioned before, some per-port callback to do the
conversion.

Thanks,
John