scsi: zfcp: fix wrong data and display format of SFP+ temperature

When implementing support for retrieval of local diagnostic data from the
FCP channel, the wrong data format was assumed for the temperature of the
local SFP+ connector. The Fibre Channel Link Services (FC-LS-3)
specification is not clear on the format of the stored integer, and only
after consulting the SNIA specification SFF-8472 did we realize it is
stored as two's complement. Thus, the used data and display format is
wrong, and highly misleading for users when the temperature should drop
below 0°C (however unlikely that may be).

To fix this, change the data format in `struct fsf_qtcb_bottom_port` from
unsigned to signed, and change the printf format string used to generate
`zfcp_sysfs_adapter_diag_sfp_temperature_show()` from `%hu` to `%hd`.

Link: https://lore.kernel.org/r/d6e3be5428da5c9490cfff4df7cae868bc9f1a7e.1582039501.git.bblock@linux.ibm.com
Fixes: a10a61e807b0 ("scsi: zfcp: support retrieval of SFP Data via Exchange Port Data")
Fixes: 6028f7c4cd87 ("scsi: zfcp: introduce sysfs interface for diagnostics of local SFP transceiver")
Cc: <stable@vger.kernel.org> # 5.5+
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Reviewed-by: Fedor Loshakov <loshakov@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/s390/scsi/zfcp_fsf.h b/drivers/s390/scsi/zfcp_fsf.h
index 2b1e4da1944f..4bfb79f20588 100644
--- a/drivers/s390/scsi/zfcp_fsf.h
+++ b/drivers/s390/scsi/zfcp_fsf.h
@@ -410,7 +410,7 @@ struct fsf_qtcb_bottom_port {
 	u8 cb_util;
 	u8 a_util;
 	u8 res2;
-	u16 temperature;
+	s16 temperature;
 	u16 vcc;
 	u16 tx_bias;
 	u16 tx_power;