From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99A13C43462 for ; Mon, 10 May 2021 09:52:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7558B610CB for ; Mon, 10 May 2021 09:52:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231180AbhEJJyC (ORCPT ); Mon, 10 May 2021 05:54:02 -0400 Received: from smtprelay0211.hostedemail.com ([216.40.44.211]:50288 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S230497AbhEJJxX (ORCPT ); Mon, 10 May 2021 05:53:23 -0400 Received: from omf15.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay01.hostedemail.com (Postfix) with ESMTP id 21A4C100E7B42; Mon, 10 May 2021 09:52:17 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: joe@perches.com) by omf15.hostedemail.com (Postfix) with ESMTPA id C6992C4184; Mon, 10 May 2021 09:52:15 +0000 (UTC) Message-ID: <7c0f57c1208b09742c839b1c1e54e2b79c83b8af.camel@perches.com> Subject: Re: [PATCH] HID: ft260: fix format type warning in ft260_word_show() From: Joe Perches To: Michael Zaidman Cc: lkp@intel.com, kbuild-all@lists.01.org, clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, jikos@kernel.org, dan.carpenter@oracle.com, linux-input@vger.kernel.org Date: Mon, 10 May 2021 02:52:14 -0700 In-Reply-To: <20210510091730.GA2276@michael-VirtualBox> References: <202105060637.LeEC6ztp-lkp@intel.com> <20210509193213.5974-1-michael.zaidman@gmail.com> <26e1929386babea33d4a320b506c5247caacde77.camel@perches.com> <20210510091730.GA2276@michael-VirtualBox> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.38.1-1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspamout04 X-Rspamd-Queue-Id: C6992C4184 X-Stat-Signature: 6ttn4yrgzpd86o1w8ng177yj47jjhw4t X-Session-Marker: 6A6F6540706572636865732E636F6D X-Session-ID: U2FsdGVkX1+pan58tWSx0z0CVolnNbeqmvoWkh/6unM= X-HE-Tag: 1620640335-659357 Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On Mon, 2021-05-10 at 12:17 +0300, Michael Zaidman wrote: > On Sun, May 09, 2021 at 01:39:29PM -0700, Joe Perches wrote: > > On Sun, 2021-05-09 at 22:32 +0300, Michael Zaidman wrote: > > > Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver") > > > > > > Fix warning reported by static analysis when built with W=1 for arm64 by > > > clang version 13.0.0 > > > > > > > > drivers/hid/hid-ft260.c:794:44: warning: format specifies type 'short' but > > >    the argument has type 'int' [-Wformat] > > >            return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field)); > > >                                              ~~~ ^~~~~~~~~~~~~~~~~~~ > > >                                              %i > > >    include/linux/byteorder/generic.h:91:21: note: expanded from > > >                                             macro 'le16_to_cpu' > > >    #define le16_to_cpu __le16_to_cpu > > >                        ^ > > >    include/uapi/linux/byteorder/big_endian.h:36:26: note: expanded from > > >                                                     macro '__le16_to_cpu' > > >    #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x)) > > >                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > >    include/uapi/linux/swab.h:105:2: note: expanded from macro '__swab16' > > >            (__builtin_constant_p((__u16)(x)) ? \ > > >            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > > > > > Signed-off-by: Michael Zaidman > > > Reported-by: kernel test robot > > > --- > > >  drivers/hid/hid-ft260.c | 2 +- > > >  1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c > > > index 047aa85a7c83..38794a29599c 100644 > > > --- a/drivers/hid/hid-ft260.c > > > +++ b/drivers/hid/hid-ft260.c > > > @@ -791,7 +791,7 @@ static int ft260_word_show(struct hid_device *hdev, int id, u8 *cfg, int len, > > >   if (ret != len && ret >= 0) > > >   return -EIO; > > >   > > > > > > - return scnprintf(buf, PAGE_SIZE, "%hi\n", le16_to_cpu(*field)); > > > + return scnprintf(buf, PAGE_SIZE, "%d\n", le16_to_cpu(*field)); > > >  } > > > > There are 2 of these so I wonder about the static analysis. > > There is nothing wrong with the static analysis. The first scnprintf format > type is perfectly valid as far as its size is greater than the size of the > data pointed by the *field pointer, which is a one byte size in our case. > The static analysis warned about the second scnprintf case, where the format > type was shorter than the integer returned by the __builtin_constant_p. > This warning can be considered as a false positive since the le16_to_cpu is > all about the 16 bits numbers, but to silence it, I submitted the above fix. $ git grep __arch_swab16 arch/arm*/ arch/arm/include/asm/swab.h:#define __arch_swab16(x) ((__u16)__arch_swahb32(x)) otherwise: static inline __attribute_const__ __u16 __fswab16(__u16 val) { #if defined (__arch_swab16) return __arch_swab16(val); #else return ___constant_swab16(val); #endif } #define ___constant_swab16(x) ((__u16)( \ (((__u16)(x) & (__u16)0x00ffU) << 8) | \ (((__u16)(x) & (__u16)0xff00U) >> 8))) /** * __swab16 - return a byteswapped 16-bit value * @x: value to byteswap */ #ifdef __HAVE_BUILTIN_BSWAP16__ #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) #else #define __swab16(x) \ (__builtin_constant_p((__u16)(x)) ? \ ___constant_swab16(x) : \ __fswab16(x)) #endif Under what condition does the ?: return an int sized value rather than a u16 sized value? I fail to see a path where the compiler should promote the returned value to int _before_ the promotion done for the varargs use. If it's for the varargs use, then both instances are promoted. > > It's probably better to use sysfs_emit as well. > > The sysfs_emit was introduced in the 5.10 kernel: > 2efc459d06f16 (Joe Perches 2020-09-16 13:40:38 -0700 335) int sysfs_emit(...) > > But, the hid-ft260 driver will be used mostly with older kernels, at least, > for the next couple of years. Since older kernel versions do not have this API, > it will require patching the driver or kernel that I would like to avoid. > Nevertheless, we can reconsider the sysfs_emit usage in this driver in the > future, upon wider 5.10+ kernels' adoption. If this is only for older kernels, then it's not really useful upstream IMO. any sprintf style use of %h or %hh for a sub int sized value isn't particularly useful as integer promotion is done on the value so it should use %d (or %i, but %i is atypical) anyway. https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/ $ git grep '%d\b' | wc -l 109922 $ git grep '%i\b' | wc -l 3508