From 6f46f718fcbe7b80ac95e4f4e1bade6efbcff84e Mon Sep 17 00:00:00 2001 From: Iustin Pop Date: Fri, 22 Feb 2019 01:20:03 +0100 Subject: 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 Reviewed-by: Lee Duncan Signed-off-by: Martin K. Petersen --- drivers/scsi/osst.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/scsi/osst.c') 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)) -- cgit v1.2.3-59-g8ed1b