[PATCH v4 8/8] ata: libata-scsi: Make ata_scsi_qc_complete() more readable

[Igor Pylypiv <ipylypiv@google.com>]

The ATA PASS-THROUGH handling logic in ata_scsi_qc_complete() is hard
to read/understand. Improve the readability of the code by moving checks
into self-explanatory boolean variables.

Additionally, always set SAM_STAT_CHECK_CONDITION when CK_COND=1 because
SAT specification mandates that SATL shall return CHECK CONDITION if
the CK_COND bit is set.

Co-developed-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Igor Pylypiv <ipylypiv@google.com>
---
 drivers/ata/libata-scsi.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a66c177b6087..8f21b3b0bc75 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -1659,26 +1659,27 @@ static void ata_scsi_qc_complete(struct ata_queued_cmd *qc)
 {
 	struct scsi_cmnd *cmd = qc->scsicmd;
 	u8 *cdb = cmd->cmnd;
-	int need_sense = (qc->err_mask != 0) &&
-		!(qc->flags & ATA_QCFLAG_SENSE_VALID);
-	int need_passthru_sense = (qc->err_mask != 0) ||
-		(qc->flags & ATA_QCFLAG_SENSE_VALID);
+	bool have_sense = qc->flags & ATA_QCFLAG_SENSE_VALID;
+	bool is_ata_passthru = cdb[0] == ATA_16 || cdb[0] == ATA_12;
+	bool is_ck_cond_request = cdb[2] & 0x20;
+	bool is_error = qc->err_mask != 0;
 
 	/* For ATA pass thru (SAT) commands, generate a sense block if
 	 * user mandated it or if there's an error.  Note that if we
-	 * generate because the user forced us to [CK_COND =1], a check
+	 * generate because the user forced us to [CK_COND=1], a check
 	 * condition is generated and the ATA register values are returned
 	 * whether the command completed successfully or not. If there
-	 * was no error, we use the following sense data:
+	 * was no error, and CK_COND=1, we use the following sense data:
 	 * sk = RECOVERED ERROR
 	 * asc,ascq = ATA PASS-THROUGH INFORMATION AVAILABLE
 	 */
-	if (((cdb[0] == ATA_16) || (cdb[0] == ATA_12)) &&
-	    ((cdb[2] & 0x20) || need_passthru_sense)) {
-		if (!(qc->flags & ATA_QCFLAG_SENSE_VALID))
+	if (is_ata_passthru && (is_ck_cond_request || is_error || have_sense)) {
+		if (!have_sense)
 			ata_gen_passthru_sense(qc);
 		ata_scsi_set_passthru_sense_fields(qc);
-	} else if (need_sense) {
+		if (is_ck_cond_request)
+			set_status_byte(qc->scsicmd, SAM_STAT_CHECK_CONDITION);
+	} else if (is_error && !have_sense) {
 		ata_gen_ata_sense(qc);
 	} else {
 		/* Keep the SCSI ML and status byte, clear host byte. */
-- 
2.45.2.803.g4e1b14247a-goog