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tty/isicom: fix big-endian compile warning
Building an arm allmodconfig kernel triggers a lengthy but harmless
warning in the isicom driver:
drvers/tty/isicom.c: In function 'isicom_send_break':
uapi/linux/swab.h:13:15: warning: integer overflow in expression [-Woverflow]
(((__u16)(x) & (__u16)0x00ffU) << 8) | \
^
uapi/linux/swab.h:107:2: note: in expansion of macro '___constant_swab16'
___constant_swab16(x) : \
^
uapi/linux/byteorder/big_endian.h:34:43: note: in expansion of macro '__swab16'
#define __cpu_to_le16(x) ((__force __le16)__swab16((x)))
^
linux/byteorder/generic.h:89:21: note: in expansion of macro '__cpu_to_le16'
#define cpu_to_le16 __cpu_to_le16
^
include/asm/io.h:270:6: note: in expansion of macro 'cpu_to_le16'
cpu_to_le16(v),__io(p)); })
^
drivers/tty/isicom.c:1058:2: note: in expansion of macro 'outw'
outw((length & 0xff00), base);
^
Apparently, the problem is related to the fact that the value 0xff00,
when used as a 16-bit number, is negative and passed into bitwise
operands of the generic byte swapping code.
Marking the input argument as unsigned in both technically correct
and avoids the warning.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>