[PATCH v10 10/15] ata: libata-scsi: add atapi_max_lun module parameter

[Phil Pemberton]

libata sets shost->max_lun to 1, so SCSI scans stop at LUN 0. Panasonic
LF-1195C and COMPAQ PD-1 drives expose their PD media on LUN 1, and
Nakamichi MJ-x.y CD changers expose a LUN for each disc slot.

Add the atapi_max_lun module parameter to set the host's scan limit.
Keep the default of 1 and clamp the value to 1..8, covering SCSI-2 LUNs
0..7. Later patches enable automatic scanning of additional LUNs for
ATAPI devices marked BLIST_FORCELUN.

Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Assisted-by: LLM
Signed-off-by: Phil Pemberton <philpem@xxxxxxxxxxxxx>
---
 drivers/ata/libata-core.c | 5 +++++
 drivers/ata/libata-scsi.c | 2 +-
 drivers/ata/libata.h      | 1 +
 include/linux/libata.h    | 1 +
 4 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 5518525357ce..f2f5ad727d20 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -123,6 +123,11 @@ int atapi_passthru16 = 1;
 module_param(atapi_passthru16, int, 0444);
 MODULE_PARM_DESC(atapi_passthru16, "Enable ATA_16 passthru for ATAPI devices (0=off, 1=on [default])");
 
+int atapi_max_lun = 1;
+module_param(atapi_max_lun, int, 0444);
+MODULE_PARM_DESC(atapi_max_lun,
+		 "Number of LUNs to scan on ATAPI devices flagged BLIST_FORCELUN (1 [default] = LUN 0 only, 8 = all SCSI-2 LUNs 0..7)");
+
 int libata_fua = 0;
 module_param_named(fua, libata_fua, int, 0444);
 MODULE_PARM_DESC(fua, "FUA support (0=off [default], 1=on)");
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 8f9aa97a519d..3131d84204ed 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -5230,7 +5230,7 @@ int ata_scsi_add_hosts(struct ata_host *host, const struct scsi_host_template *s
 		shost->transportt = &ata_scsi_transportt;
 		shost->unique_id = ap->print_id;
 		shost->max_id = 16;
-		shost->max_lun = 1;
+		shost->max_lun = clamp(atapi_max_lun, 1, ATAPI_MAX_LUN);
 		shost->max_channel = 1;
 		shost->max_cmd_len = 32;
 
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 48274691cd0e..aedc6b61196b 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -33,6 +33,7 @@ enum {
 #define ATA_PORT_TYPE_NAME	"ata_port"
 
 extern int atapi_passthru16;
+extern int atapi_max_lun;
 extern int libata_fua;
 extern int libata_noacpi;
 extern int libata_allow_tpm;
diff --git a/include/linux/libata.h b/include/linux/libata.h
index 48bde275968d..03511280800f 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -180,6 +180,7 @@ enum {
 	ATA_SHORT_PAUSE		= 16,
 
 	ATAPI_MAX_DRAIN		= 16 << 10,
+	ATAPI_MAX_LUN		= 8,	/* SCSI-2 cap (LUN values 0..7) */
 
 	ATA_ALL_DEVICES		= (1 << ATA_MAX_DEVICES) - 1,
 
-- 
2.43.0