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Subjectlibata: Simulate REPORT LUNS for ATAPI devices when not supported
The Quantum GoVault SATAPI removable disk device returns ATA_ERR in
response to a REPORT LUNS packet. If this happens to an ATAPI device
that is attached to a SAS controller (this is the case with sas_ata),
the device does not load because SCSI won't touch a "SCSI device"
that won't report its LUNs. If we see this command fail, we should
simulate a response that indicates the presence of LUN 0.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
drivers/ata/libata-core.c | 36 ++++++++++++++++++++++++++++++++----
drivers/ata/libata-scsi.c | 4 ++--
include/linux/libata.h | 2 ++
3 files changed, 36 insertions(+), 6 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 915a55a..a3d6217 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4455,6 +4455,35 @@ void ata_qc_complete(struct ata_queued_c
{
struct ata_port *ap = qc->ap;

+ /*
+ * If this is an ATAPI device that fails a REPORT LUN issued by SCSI,
+ * assume that LUN 0 exists and fake the return buffer as appropriate.
+ * ATA devices have REPORT LUN simulated for them.
+ */
+ if (is_atapi_taskfile(&qc->tf) &&
+ qc->scsicmd &&
+ qc->cdb[0] == REPORT_LUNS &&
+ qc->err_mask) {
+ unsigned int buflen;
+ struct scsi_cmnd *cmd = qc->scsicmd;
+ u8 *buf = NULL;
+
+ buflen = ata_scsi_rbuf_get(cmd, &buf);
+ memset(buf, 0, buflen);
+ buf[3] = 8;
+ ata_scsi_rbuf_put(cmd, buf);
+
+ qc->err_mask = 0;
+
+ /* read result TF if requested */
+ if (qc->flags & ATA_QCFLAG_RESULT_TF)
+ ap->ops->tf_read(ap, &qc->result_tf);
+ qc->result_tf.command &= ~ATA_ERR;
+ qc->flags &= ~ATA_QCFLAG_RESULT_TF;
+
+ goto finish_qc;
+ }
+
/* XXX: New EH and old EH use different mechanisms to
* synchronize EH with regular execution path.
*
@@ -4486,8 +4515,6 @@ void ata_qc_complete(struct ata_queued_c
/* read result TF if requested */
if (qc->flags & ATA_QCFLAG_RESULT_TF)
ap->ops->tf_read(ap, &qc->result_tf);
-
- __ata_qc_complete(qc);
} else {
if (qc->flags & ATA_QCFLAG_EH_SCHEDULED)
return;
@@ -4495,9 +4522,10 @@ void ata_qc_complete(struct ata_queued_c
/* read result TF if failed or requested */
if (qc->err_mask || qc->flags & ATA_QCFLAG_RESULT_TF)
ap->ops->tf_read(ap, &qc->result_tf);
-
- __ata_qc_complete(qc);
}
+
+finish_qc:
+ __ata_qc_complete(qc);
}

/**
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index 47ea111..da013a7 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1639,7 +1639,7 @@ defer:
* Length of response buffer.
*/

-static unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
+unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out)
{
u8 *buf;
unsigned int buflen;
@@ -1670,7 +1670,7 @@ static unsigned int ata_scsi_rbuf_get(st
* spin_lock_irqsave(host lock)
*/

-static inline void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, u8 *buf)
+void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, u8 *buf)
{
if (cmd->use_sg) {
struct scatterlist *sg;
diff --git a/include/linux/libata.h b/include/linux/libata.h
index abd2deb..b37b21f 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -723,6 +723,8 @@ extern int ata_scsi_detect(struct scsi_h
extern int ata_scsi_ioctl(struct scsi_device *dev, int cmd, void __user *arg);
extern int ata_scsi_queuecmd(struct scsi_cmnd *cmd, void (*done)(struct scsi_cmnd *));
extern int ata_scsi_release(struct Scsi_Host *host);
+unsigned int ata_scsi_rbuf_get(struct scsi_cmnd *cmd, u8 **buf_out);
+void ata_scsi_rbuf_put(struct scsi_cmnd *cmd, u8 *buf);
extern void ata_sas_port_destroy(struct ata_port *);
extern struct ata_port *ata_sas_port_alloc(struct ata_host *,
struct ata_port_info *, struct Scsi_Host *);
-
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