linux-kernel - Re: [PATCH v8 4/4] gpio: xilinx: Utilize for_each_set

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Message-ID: <20200619090500.GC2428291@smile.fi.intel.com>
Date:   Fri, 19 Jun 2020 12:05:00 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Syed Nayyar Waris <syednwaris@...il.com>
Cc:     kernel test robot <lkp@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kbuild-all@...ts.01.org,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michal Simek <michal.simek@...inx.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 4/4] gpio: xilinx: Utilize for_each_set_clump macro

On Fri, Jun 19, 2020 at 11:38:59AM +0300, Andy Shevchenko wrote:
> On Fri, Jun 19, 2020 at 10:02 AM Syed Nayyar Waris <syednwaris@...il.com> wrote:
> 
> ...
> 
> > > config: sparc64-randconfig-s032-20200615 (attached as .config)
> > > compiler: sparc64-linux-gcc (GCC) 9.3.0
> > > reproduce:
> > >         # apt-get install sparse
> > >         # sparse version: v0.6.2-rc1-3-g55607964-dirty
> > >         # save the attached .config to linux build tree
> > >         make W=1 C=1 ARCH=sparc64 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__'
> 
> ...
> 
> > > sparse warnings: (new ones prefixed by >>)
> > >
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > >    include/linux/bitmap.h:594:63: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:639:45: sparse: sparse: shift too big (64) for type unsigned long
> > > >> include/linux/bitmap.h:638:17: sparse: sparse: invalid access past the end of 'old' (8 8)
> 
> > It seems to me that to reproduce this warning, I have to use the
> > sparc64 compiler. I have installed 'sparc64-linux-gnu-gcc' on my
> > computer.
> 
> Sparse is not a compiler.

On x86_64:

  CHECK   drivers/gpio/gpio-xilinx.c
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:594:63: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:639:45: warning: shift too big (64) for type unsigned long
  include/linux/bitmap.h:638:17: warning: invalid access past the end of 'old' (8 8)

> > I have to specify that this compiler needs to be used for build
> > process. How/ Where do I specify this?
> >
> > I have downloaded the config.gz (has config file) and placed it at the
> > root of the linux kernel project tree. But the Makefile STILL has
> > 'gcc' as the compiler. When I build, it is the 'gcc' compiler being
> > used and not 'sparc64-linux-gnu-gcc'. I know I can manually change the
> > Makefile to use sparc64 compiler, but I think there must be some more
> > elegant way to do this, perhaps using make menuconfig?
> 
> If you wish to run a compilation, download a compiler from [1], and,
> after adding its bin/ folder to PATH, run
> make CROSS_COMPILE=sparc64-linux- ARCH=sparc64 ... # first generate .config
> 
> > Kindly illuminate as to how shall I reproduce the compiler warning.
> 
> > > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @638           map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
> > > 803024b6c8a375 Syed Nayyar Waris      2020-06-15 @639           map[index + 1] |= (value >> space);
> 
> Hmm... I think I sent a reply [2] where I explained how space can be
> 64. Do you agree with analysis?
> 
> [1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
> [2]: https://lore.kernel.org/lkml/20200616081428.GP2428291@smile.fi.intel.com/

-- 
With Best Regards,
Andy Shevchenko