From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S939642AbdD1IdZ (ORCPT ); Fri, 28 Apr 2017 04:33:25 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55620 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424851AbdD1Ib1 (ORCPT ); Fri, 28 Apr 2017 04:31:27 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann Subject: [PATCH 4.4 05/17] tty: nozomi: avoid a harmless gcc warning Date: Fri, 28 Apr 2017 10:30:18 +0200 Message-Id: <20170428082911.047502434@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170428082910.160564394@linuxfoundation.org> References: <20170428082910.160564394@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Arnd Bergmann commit a4f642a8a3c2838ad09fe8313d45db46600e1478 upstream. The nozomi wireless data driver has its own helper function to transfer data from a FIFO, doing an extra byte swap on big-endian architectures, presumably to bring the data back into byte-serial order after readw() or readl() perform their implicit byteswap. This helper function is used in the receive_data() function to first read the length into a 32-bit variable, which causes a compile-time warning: drivers/tty/nozomi.c: In function 'receive_data': drivers/tty/nozomi.c:857:9: warning: 'size' may be used uninitialized in this function [-Wmaybe-uninitialized] The problem is that gcc is unsure whether the data was actually read or not. We know that it is at this point, so we can replace it with a single readl() to shut up that warning. I am leaving the byteswap in there, to preserve the existing behavior, even though this seems fishy: Reading the length of the data into a cpu-endian variable should normally not use a second byteswap on big-endian systems, unless the hardware is aware of the CPU endianess. There appears to be a lot more confusion about endianess in this driver, so it probably has not worked on big-endian systems in a long time, if ever, and I have no way to test it. It's well possible that this driver has not been used by anyone in a while, the last patch that looks like it was tested on the hardware is from 2008. Signed-off-by: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman --- drivers/tty/nozomi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/tty/nozomi.c +++ b/drivers/tty/nozomi.c @@ -823,7 +823,7 @@ static int receive_data(enum port_type i struct tty_struct *tty = tty_port_tty_get(&port->port); int i, ret; - read_mem32((u32 *) &size, addr, 4); + size = __le32_to_cpu(readl(addr)); /* DBG1( "%d bytes port: %d", size, index); */ if (tty && test_bit(TTY_THROTTLED, &tty->flags)) {