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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Rui Miguel Silva <rui.silva@linaro.org>
Cc: kernel test robot <lkp@intel.com>,
	clang-built-linux@googlegroups.com, kbuild-all@lists.01.org,
	linux-usb@vger.kernel.org
Subject: Re: [usb:usb-testing 54/97] drivers/usb/isp1760/isp1760-hcd.c:735:2: warning: Value stored to 'scratch' is never read [clang-analyzer-deadcode.DeadStores]
Date: Thu, 19 Aug 2021 16:59:04 +0200	[thread overview]
Message-ID: <YR5xuManlukIAf3L@kroah.com> (raw)
In-Reply-To: <CDNBNHH65Z6Z.3P3H9W04XAHDB@arch-thunder>

On Thu, Aug 19, 2021 at 08:47:37AM +0100, Rui Miguel Silva wrote:
> Hi,
> On Wed Aug 18, 2021 at 11:09 PM WEST, kernel test robot wrote:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> > head:   e4788edc730a0d2b26e1ae1f08fbb3f635b92dbb
> > commit: 7de14c88272c05d86fce83a5cead36832ce3a424 [54/97] usb: isp1760: remove debug message as error
> > config: riscv-randconfig-c006-20210818 (attached as .config)
> > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project d2b574a4dea5b718e4386bf2e26af0126e5978ce)
> > reproduce (this is a W=1 build):
> >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> >         chmod +x ~/bin/make.cross
> >         # install riscv cross compiling tool for clang build
> >         # apt-get install binutils-riscv64-linux-gnu
> >         # https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/?id=7de14c88272c05d86fce83a5cead36832ce3a424
> >         git remote add usb https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
> >         git fetch --no-tags usb usb-testing
> >         git checkout 7de14c88272c05d86fce83a5cead36832ce3a424
> >         # save the attached .config to linux build tree
> >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=riscv clang-analyzer 
> >
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <lkp@intel.com>
> >
> >
> > clang-analyzer warnings: (new ones prefixed by >>)
> >                    ^      ~
> >    drivers/target/target_core_configfs.c:2627:23: warning: Value stored to 'alua_lu_gp_cg' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
> >            struct config_group *alua_lu_gp_cg = &lu_gp->lu_gp_group;
> >                                 ^~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:2627:23: note: Value stored to 'alua_lu_gp_cg' during its initialization is never read
> >            struct config_group *alua_lu_gp_cg = &lu_gp->lu_gp_group;
> >                                 ^~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:2731:2: warning: Value stored to 'alua_lu_gp_ci' is never read [clang-analyzer-deadcode.DeadStores]
> >            alua_lu_gp_ci = &alua_lu_gp_cg->cg_item;
> >            ^               ~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:2731:2: note: Value stored to 'alua_lu_gp_ci' is never read
> >            alua_lu_gp_ci = &alua_lu_gp_cg->cg_item;
> >            ^               ~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:2748:25: warning: Value stored to 'lu_gp' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
> >            struct t10_alua_lu_gp *lu_gp = container_of(to_config_group(item),
> >                                   ^~~~~
> >    drivers/target/target_core_configfs.c:2748:25: note: Value stored to 'lu_gp' during its initialization is never read
> >            struct t10_alua_lu_gp *lu_gp = container_of(to_config_group(item),
> >                                   ^~~~~
> >    drivers/target/target_core_configfs.c:3026:23: warning: Value stored to 'alua_tg_pt_gp_cg' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
> >            struct config_group *alua_tg_pt_gp_cg = &tg_pt_gp->tg_pt_gp_group;
> >                                 ^~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:3026:23: note: Value stored to 'alua_tg_pt_gp_cg' during its initialization is never read
> >            struct config_group *alua_tg_pt_gp_cg = &tg_pt_gp->tg_pt_gp_group;
> >                                 ^~~~~~~~~~~~~~~~   ~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:3163:2: warning: Value stored to 'alua_tg_pt_gp_ci' is never read [clang-analyzer-deadcode.DeadStores]
> >            alua_tg_pt_gp_ci = &alua_tg_pt_gp_cg->cg_item;
> >            ^                  ~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:3163:2: note: Value stored to 'alua_tg_pt_gp_ci' is never read
> >            alua_tg_pt_gp_ci = &alua_tg_pt_gp_cg->cg_item;
> >            ^                  ~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/target/target_core_configfs.c:3179:28: warning: Value stored to 'tg_pt_gp' during its initialization is never read [clang-analyzer-deadcode.DeadStores]
> >            struct t10_alua_tg_pt_gp *tg_pt_gp = container_of(to_config_group(item),
> >                                      ^~~~~~~~
> >    drivers/target/target_core_configfs.c:3179:28: note: Value stored to 'tg_pt_gp' during its initialization is never read
> >            struct t10_alua_tg_pt_gp *tg_pt_gp = container_of(to_config_group(item),
> >                                      ^~~~~~~~
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    6 warnings generated.
> >    drivers/misc/eeprom/at24.c:334:2: warning: Value stored to 'client' is never read [clang-analyzer-deadcode.DeadStores]
> >            client = at24_client->client;
> >            ^        ~~~~~~~~~~~~~~~~~~~
> >    drivers/misc/eeprom/at24.c:334:2: note: Value stored to 'client' is never read
> >            client = at24_client->client;
> >            ^        ~~~~~~~~~~~~~~~~~~~
> >    drivers/misc/eeprom/at24.c:397:2: warning: Value stored to 'client' is never read [clang-analyzer-deadcode.DeadStores]
> >            client = at24_client->client;
> >            ^        ~~~~~~~~~~~~~~~~~~~
> >    drivers/misc/eeprom/at24.c:397:2: note: Value stored to 'client' is never read
> >            client = at24_client->client;
> >            ^        ~~~~~~~~~~~~~~~~~~~
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    5 warnings generated.
> >    drivers/usb/isp1760/isp1760-core.c:490:2: warning: Value stored to 'udc_enabled' is never read [clang-analyzer-deadcode.DeadStores]
> >            udc_enabled = ((devflags & ISP1760_FLAG_ISP1763) ||
> >            ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    drivers/usb/isp1760/isp1760-core.c:490:2: note: Value stored to 'udc_enabled' is never read
> >            udc_enabled = ((devflags & ISP1760_FLAG_ISP1763) ||
> >            ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    4 warnings generated.
> >    Suppressed 4 warnings (4 in non-user code).
> >    Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
> >    9 warnings generated.
> > >> drivers/usb/isp1760/isp1760-hcd.c:735:2: warning: Value stored to 'scratch' is never read [clang-analyzer-deadcode.DeadStores]
> >            scratch = isp1760_hcd_read(hcd, HC_CHIP_ID_HIGH);
> >            ^         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> yeah, this is desired behaviour, this read is only to make sure  that
> we make something different than the pattern to test go over the bus.
> However I will take a look to this warning and other clang warnings
> that I am seeing in this report.

This is why I hate this type of warning, doing a read like this is
totally normal for drivers.  Compilers that think this is something they
can ignore or warn about are just wrong.

greg k-h

  reply	other threads:[~2021-08-19 14:59 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 22:09 [usb:usb-testing 54/97] drivers/usb/isp1760/isp1760-hcd.c:735:2: warning: Value stored to 'scratch' is never read [clang-analyzer-deadcode.DeadStores] kernel test robot
2021-08-19  7:47 ` Rui Miguel Silva
2021-08-19 14:59   ` Greg Kroah-Hartman [this message]
2021-08-19 15:06     ` Alan Stern

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