Re: [PATCH v5 5/6] ata: libata-scsi: probe additional LUNs for multi-LUN ATAPI devices

[Hannes Reinecke <hare@suse.de>]

On 5/12/26 22:27, Phil Pemberton wrote:
> After LUN 0 is added for an ATAPI device, check its BLIST_FORCELUN
> flag.  If set, bump dev->nr_luns to the host's max_lun so the LUN
> routing in atapi_xlat() accepts the probe INQUIRYs, then call
> scsi_scan_target() with SCAN_WILD_CARD to trigger the SCSI layer's
> built-in sequential LUN scan for that target only.  This probes
> LUNs 1..shost->max_lun, driven by the libata atapi_max_lun module
> parameter.
> 
> Devices without BLIST_FORCELUN (the vast majority of ATAPI devices)
> are left with only LUN 0 -- no sequential scan is triggered, so
> single-LUN devices like the iHAS124 DVD writer are completely
> unaffected.
> 
> Non-responding LUNs (PQ=0/PDT=0x1f) are silently skipped by
> scsi_probe_and_add_lun() when BLIST_NO_LUN_1F is set on the device
> via scsi_devinfo.
> 
> Signed-off-by: Phil Pemberton <philpem@philpem.me.uk>
> ---
>   drivers/ata/libata-scsi.c | 27 +++++++++++++++++++++++----
>   1 file changed, 23 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 2d714efc855f..a6f5557014c7 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -26,6 +26,7 @@
>   #include <scsi/scsi_device.h>
>   #include <scsi/scsi_tcq.h>
>   #include <scsi/scsi_transport.h>
> +#include <scsi/scsi_devinfo.h>
>   #include <linux/libata.h>
>   #include <linux/hdreg.h>
>   #include <linux/uaccess.h>
> @@ -4745,12 +4746,30 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
>   			sdev = __scsi_add_device(ap->scsi_host, channel, id, 0,
>   						 NULL);
>   			if (!IS_ERR(sdev)) {
> -				dev->sdev[0] = sdev;
> -				ata_scsi_assign_ofnode(dev, ap);
> +				/*
> +				 * For multi-LUN ATAPI (BLIST_FORCELUN), bump
> +				 * dev->nr_luns to the host max so the LUN
> +				 * routing in atapi_xlat() accepts the probe
> +				 * INQUIRYs to LUN > 0, then trigger the
> +				 * sequential scan.  pdt_1f_for_no_lun, set
> +				 * during LUN 0 configure, ensures
> +				 * non-responding LUNs are silently skipped;
> +				 * dev->sdev[] is populated by
> +				 * ata_scsi_dev_config() during the scan.
> +				 */
> +				if (dev->class == ATA_DEV_ATAPI &&
> +				    sdev->sdev_bflags & BLIST_FORCELUN) {
> +					dev->nr_luns = ap->scsi_host->max_lun;
> +					scsi_scan_target(
> +						&ap->scsi_host->shost_gendev,
> +						channel, id, SCAN_WILD_CARD,
> +						SCSI_SCAN_RESCAN);
> +				}

Again, nr_luns is not required here.
We only need to check that host->max_lun does not exceed ATAPI_MAX_LUN.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich