Re: [PATCH 3/3] ata: libata-scsi: probe additional LUNs for multi-LUN ATAPI devices

Damien Le Moal
2026-04-12T07:41:11Z

On 4/9/26 23:05, Phil Pemberton wrote:
> Some ATAPI devices (e.g. the Panasonic PD/CD combo drives) implement
> multiple logical units. For instance the aforementioned PD/CD has a CD
> drive on LUN 0 and the rewritable Phase-change Dual (PD) block device on
> LUN 1.
>
> ata_scsi_scan_host() previously only scanned LUN 0 via
> __scsi_add_device(). With the multi-LUN work now in place, extend this
> scan to probe for additional LUNs on devices which have BLIST_FORCELUN
> set in the SCSI device info table.
>
> Scanning stops when __scsi_add_device() fails, or the device reports
> device type 0x1f (unknown or no device type). The PD drive returns this
> for unimplemented LUNs.
>
> The aforementioned BLIST_FORCELUN guard prevents non-multilun devices
> from being affected.
>
> Tested with a Panasonic LF-1195C PD/CD with Compaq firmware, which now
> correctly enumerates as a CD drive (sr) and PD optical drive (sd).
>
> Also tested with a LITE-ON iHAS124 DVD drive, which has a single LUN and
> ignores the LUN parameter in the CDB. As a result, without the
> BLIST_FORCELUN guard, this drive would pop up as eight separate devices.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Phil Pemberton <philpem@philpem.me.uk>
> ---
> drivers/ata/libata-scsi.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index dc6829e60fb3..0a7ce44118fe 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -4732,6 +4732,35 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
> if (!IS_ERR(sdev)) {
> dev->sdev = sdev;
> ata_scsi_assign_ofnode(dev, ap);
> + /*
> + * Multi-LUN ATAPI devices (e.g. PD/CD combo
> + * drives) are flagged BLIST_FORCELUN in
> + * scsi_devinfo. Probe additional LUNs when
> + * the flag is set.
> + */
> + if (dev->class == ATA_DEV_ATAPI &&
> + (sdev->sdev_bflags & BLIST_FORCELUN)) {
> + u64 lun;
> +
> + for (lun = 1; lun < ap->scsi_host->max_lun;
> + lun++) {
> + struct scsi_device *extra;
> +
> + extra = __scsi_add_device(
> + ap->scsi_host,
> + channel, id, lun,
> + NULL);
> + if (IS_ERR(extra))
> + break;
> + /* PDT 0x1f: no device type */
> + if (extra->type == 0x1f) {
> + scsi_remove_device(extra);
> + scsi_device_put(extra);
> + break;
> + }
> + scsi_device_put(extra);
> + }
> + }

It would be a lot nicer and more readable to have this hunk as a helper
function, e.g.: ata_scsi_scan_atapi_luns().

> scsi_device_put(sdev);
> } else {
> dev->sdev = NULL;

--
Damien Le Moal
Western Digital Research