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| author | Iustin Pop <iustin@k1024.org> | 2019-02-22 01:20:03 +0100 |
|---|---|---|
| committer | Martin K. Petersen <martin.petersen@oracle.com> | 2019-02-27 09:10:16 -0500 |
| commit | 6f46f718fcbe7b80ac95e4f4e1bade6efbcff84e (patch) | |
| tree | efec70cd0a6b86782511270426eced9cad412f79 | |
| parent | 5c17f87abb1a86eb4d2a108477e56389622cf195 (diff) | |
| download | linux-6f46f718fcbe7b80ac95e4f4e1bade6efbcff84e.tar.bz2 | |
scsi: st: osst: Remove negative constant left-shifts
Negative constant left-shift is undefined behaviour in the C standard, and
as such newer versions of clang (at least) warn against it. GCC supports it
for a long time, but it would be better to remove it and rely on defined
behaviour.
My understanding is "~(-1 << N)" in 2's complement is intended to generate
a bit pattern of zeroes ending with N '1' bits. The same can be achieved by
"(1 << N) - 1" in a well-defined way, so switch to it to remove the
warning.
Tested: building a kernel with generic SCSI tape, and checking basic
operations (mt status, mt eject) on a real LTO unit. Cannot test the osst
driver.
Signed-off-by: Iustin Pop <iustin@k1024.org>
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
| -rw-r--r-- | drivers/scsi/osst.c | 2 | ||||
| -rw-r--r-- | drivers/scsi/st.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/drivers/scsi/osst.c b/drivers/scsi/osst.c index 664c1238a87f..be3c73ebbfde 100644 --- a/drivers/scsi/osst.c +++ b/drivers/scsi/osst.c @@ -139,7 +139,7 @@ static int debugging = 1; #define OSST_TIMEOUT (200 * HZ) #define OSST_LONG_TIMEOUT (1800 * HZ) -#define TAPE_NR(x) (iminor(x) & ~(-1 << ST_MODE_SHIFT)) +#define TAPE_NR(x) (iminor(x) & ((1 << ST_MODE_SHIFT)-1)) #define TAPE_MODE(x) ((iminor(x) & ST_MODE_MASK) >> ST_MODE_SHIFT) #define TAPE_REWIND(x) ((iminor(x) & 0x80) == 0) #define TAPE_IS_RAW(x) (TAPE_MODE(x) & (ST_NBR_MODES >> 1)) diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c index 7c7a742a5ef7..19c022e66d63 100644 --- a/drivers/scsi/st.c +++ b/drivers/scsi/st.c @@ -169,7 +169,7 @@ static int debugging = DEBUG; /* Remove mode bits and auto-rewind bit (7) */ #define TAPE_NR(x) ( ((iminor(x) & ~255) >> (ST_NBR_MODE_BITS + 1)) | \ - (iminor(x) & ~(-1 << ST_MODE_SHIFT)) ) + (iminor(x) & ((1 << ST_MODE_SHIFT)-1))) #define TAPE_MODE(x) ((iminor(x) & ST_MODE_MASK) >> ST_MODE_SHIFT) /* Construct the minor number from the device (d), mode (m), and non-rewind (n) data */ |