libata: add support for ATA_16 on ATAPI

Add support for issuing ATA_16 passthru commands to ATAPI devices
managed by libata.  It requires the previous CDB length fix patch.

A boot/module parameter, "atapi_passthru16=0" can be used to globally
disable this feature, if ever desired.

tj: restructured __ata_scsi_queuecmd() according to Jeff's suggestion.

Signed-off-by: Mark Lord <liml@rtr.ca>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

3 files changed, 41 insertions, 16 deletions

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index fc0679370638..75ccf46972d8 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -86,6 +86,10 @@ int atapi_dmadir = 0;
 module_param(atapi_dmadir, int, 0444);
 MODULE_PARM_DESC(atapi_dmadir, "Enable ATAPI DMADIR bridge support (0=off, 1=on)");
 
+int atapi_passthru16 = 1;
+module_param(atapi_passthru16, int, 0444);
+MODULE_PARM_DESC(atapi_passthru16, "Enable ATA_16 passthru for ATAPI devices; on by default (0=off, 1=on)");
+
 int libata_fua = 0;
 module_param_named(fua, libata_fua, int, 0444);
 MODULE_PARM_DESC(fua, "FUA support (0=off, 1=on)");
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 58051ee40f1a..7d66c986a54c 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2761,28 +2761,48 @@ static inline int __ata_scsi_queuecmd(struct scsi_cmnd *scmd,
                                       void (*done)(struct scsi_cmnd *),
                                       struct ata_device *dev)
 {
+        u8 scsi_op = scmd->cmnd[0];
+        ata_xlat_func_t xlat_func;
         int rc = 0;
 
-        if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len)) {
-                DPRINTK("bad CDB len=%u, max=%u\n",
-                        scmd->cmd_len, dev->cdb_len);
-                scmd->result = DID_ERROR << 16;
-                done(scmd);
-                return 0;
-        }
-
         if (dev->class == ATA_DEV_ATA) {
-                ata_xlat_func_t xlat_func = ata_get_xlat_func(dev,
-                                                              scmd->cmnd[0]);
+                if (unlikely(!scmd->cmd_len || scmd->cmd_len > dev->cdb_len))
+                        goto bad_cdb_len;
 
-                if (xlat_func)
-                        rc = ata_scsi_translate(dev, scmd, done, xlat_func);
-                else
-                        ata_scsi_simulate(dev, scmd, done);
-        } else
-                rc = ata_scsi_translate(dev, scmd, done, atapi_xlat);
+                xlat_func = ata_get_xlat_func(dev, scsi_op);
+        } else {
+                if (unlikely(!scmd->cmd_len))
+                        goto bad_cdb_len;
+
+                xlat_func = NULL;
+                if (likely((scsi_op != ATA_16) || !atapi_passthru16)) {
+                        /* relay SCSI command to ATAPI device */
+                        if (unlikely(scmd->cmd_len > dev->cdb_len))
+                                goto bad_cdb_len;
+
+                        xlat_func = atapi_xlat;
+                } else {
+                        /* ATA_16 passthru, treat as an ATA command */
+                        if (unlikely(scmd->cmd_len > 16))
+                                goto bad_cdb_len;
+
+                        xlat_func = ata_get_xlat_func(dev, scsi_op);
+                }
+        }
+
+        if (xlat_func)
+                rc = ata_scsi_translate(dev, scmd, done, xlat_func);
+        else
+                ata_scsi_simulate(dev, scmd, done);
 
         return rc;
+
+ bad_cdb_len:
+        DPRINTK("bad CDB len=%u, scsi_op=0x%02x, max=%u\n",
+                scmd->cmd_len, scsi_op, dev->cdb_len);
+        scmd->result = DID_ERROR << 16;
+        done(scmd);
+        return 0;
 }
 
 /**
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 6d85edefa7c6..11f64a43b38a 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -56,6 +56,7 @@ extern unsigned int ata_print_id;
 extern struct workqueue_struct *ata_aux_wq;
 extern int atapi_enabled;
 extern int atapi_dmadir;
+extern int atapi_passthru16;
 extern int libata_fua;
 extern int libata_noacpi;
 extern struct ata_queued_cmd *ata_qc_new_init(struct ata_device *dev);