Patch "tty/isicom: fix big-endian compile warning" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

tty/isicom: fix big-endian compile warning

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tty-isicom-fix-big-endian-compile-warning.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Arnd Bergmann <[email protected]>
Date: Tue, 13 Jan 2015 22:59:47 +0100
Subject: tty/isicom: fix big-endian compile warning

From: Arnd Bergmann <[email protected]>

commit f3e2d56dce47dbd0bb3f69f84741b439542fef37 upstream.

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.

---
 drivers/tty/isicom.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -1055,7 +1055,7 @@ static int isicom_send_break(struct tty_
 
 	outw(0x8000 | ((port->channel) << (card->shift_count)) | 0x3, base);
 	outw((length & 0xff) << 8 | 0x00, base);
-	outw((length & 0xff00), base);
+	outw((length & 0xff00u), base);
 	InterruptTheCard(base);
 
 	unlock_card(card);

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/ib-iser-fix-sparse-warnings.patch queue-3.18/cred-userns-define-current_user_ns-as-a-function.patch queue-3.18/pci-xilinx-fix-harmless-format-string-warning.patch queue-3.18/arm64-build-vdso-without-libgcov.patch queue-3.18/arm64-provide-a-namespace-to-ncaps.patch queue-3.18/alsa-ppc-awacs-shut-up-maybe-uninitialized-warning.patch queue-3.18/net-tg3-avoid-uninitialized-variable-warning.patch queue-3.18/tty-isicom-fix-big-endian-compile-warning.patch queue-3.18/mtd-avoid-stack-overflow-in-mtd-cfi-code.patch queue-3.18/ib-qib-rename-bits_per_page-to-rvt_bits_per_page.patch queue-3.18/ips-remove-pointless-warning.patch queue-3.18/powerpc-ptrace-fix-out-of-bounds-array-access-warning.patch queue-3.18/staging-imx-drm-fix-indentation-warning.patch queue-3.18/mlx5-avoid-build-warnings-on-32-bit.patch queue-3.18/mm-cma-silence-warnings-due-to-max-usage.patch queue-3.18/misdn-avoid-arch-specific-__builtin_return_address-call.patch queue-3.18/staging-bcm-add-32-bit-host-dependency.patch queue-3.18/staging-vt6655-fix-overly-large-stack-usage.patch queue-3.18/drbd-avoid-redefinition-of-bits_per_page.patch queue-3.18/infiniband-mlx5-avoid-a-compile-time-warning.patch queue-3.18/arm-cns3xxx-shut-up-frame-size-warning.patch queue-3.18/ib-ehca-fix-maybe-uninitialized-warnings.patch