From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: kernel test robot <lkp@intel.com>,
kbuild-all@lists.01.org, clang-built-linux@googlegroups.com,
linux-kernel@vger.kernel.org,
Mauro Carvalho Chehab <mchehab@kernel.org>,
linux-media@vger.kernel.org
Subject: Re: drivers/media/pci/intel/ipu3/ipu3-cio2.c:163:56: warning: implicit conversion from 'unsigned long' to 'u16' (aka 'unsigned short') changes value from 131072 to 0
Date: Mon, 14 Dec 2020 17:29:55 +0200 [thread overview]
Message-ID: <20201214152955.GH4077@smile.fi.intel.com> (raw)
In-Reply-To: <20201211165614.GC26370@paasikivi.fi.intel.com>
On Fri, Dec 11, 2020 at 06:56:14PM +0200, Sakari Ailus wrote:
> On Mon, Nov 23, 2020 at 12:40:18PM +0200, Andy Shevchenko wrote:
> > On Sat, Nov 21, 2020 at 04:23:05PM +0800, kernel test robot wrote:
...
> > > All warnings (new ones prefixed by >>):
> > >
> > > >> drivers/media/pci/intel/ipu3/ipu3-cio2.c:163:56: warning: implicit conversion from 'unsigned long' to 'u16' (aka 'unsigned short') changes value from 131072 to 0 [-Wconstant-conversion]
> > > entry[1].second_entry.num_of_pages = CIO2_LOP_ENTRIES * CIO2_MAX_LOPS;
> > > ~ ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
> > > 1 warning generated.
> >
> > Okay, now we have an interesting case. The IP is quite unlikely be used on
> > ARM64, but my patches made the clear picture about use of PAGE_SIZE here.
> >
> > So, I see at least the following options to mitigate the above, i.e.:
> > 1/ reduce driver scope to X86
> > 2/ fix the variables to be wider type to be able to hold PAGE_SIZE > 4k
> > 3/ switch to custom PAGE_SIZE / _SHIFT / _MASK and accompanying macros
> >
> > And I still consider 3/ is silly move because as we see the driver was
> > never assumed to work with big page sizes (besides unsigned short type
> > here, PAGE_SHIFT and PAGE_MASK in the original code was as is and on ARM64
> > they compiled to 0 values w/o warnings, effectively make the driver
> > improperly functioning anyway).
>
> Apologies for the late answer.
>
> I think I'd favour the first option. It's not really useful to be able to
> compile this elsewhere; as such the driver doesn't do anything special that
> would make it prone to breakage through changes elsewhere.
>
> Would you like to send a patch? :-)
Done.
--
With Best Regards,
Andy Shevchenko
WARNING: multiple messages have this Message-ID (diff)
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: kbuild-all@lists.01.org
Subject: Re: drivers/media/pci/intel/ipu3/ipu3-cio2.c:163:56: warning: implicit conversion from 'unsigned long' to 'u16' (aka 'unsigned short') changes value from 131072 to 0
Date: Mon, 14 Dec 2020 17:29:55 +0200 [thread overview]
Message-ID: <20201214152955.GH4077@smile.fi.intel.com> (raw)
In-Reply-To: <20201211165614.GC26370@paasikivi.fi.intel.com>
[-- Attachment #1: Type: text/plain, Size: 1814 bytes --]
On Fri, Dec 11, 2020 at 06:56:14PM +0200, Sakari Ailus wrote:
> On Mon, Nov 23, 2020 at 12:40:18PM +0200, Andy Shevchenko wrote:
> > On Sat, Nov 21, 2020 at 04:23:05PM +0800, kernel test robot wrote:
...
> > > All warnings (new ones prefixed by >>):
> > >
> > > >> drivers/media/pci/intel/ipu3/ipu3-cio2.c:163:56: warning: implicit conversion from 'unsigned long' to 'u16' (aka 'unsigned short') changes value from 131072 to 0 [-Wconstant-conversion]
> > > entry[1].second_entry.num_of_pages = CIO2_LOP_ENTRIES * CIO2_MAX_LOPS;
> > > ~ ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
> > > 1 warning generated.
> >
> > Okay, now we have an interesting case. The IP is quite unlikely be used on
> > ARM64, but my patches made the clear picture about use of PAGE_SIZE here.
> >
> > So, I see at least the following options to mitigate the above, i.e.:
> > 1/ reduce driver scope to X86
> > 2/ fix the variables to be wider type to be able to hold PAGE_SIZE > 4k
> > 3/ switch to custom PAGE_SIZE / _SHIFT / _MASK and accompanying macros
> >
> > And I still consider 3/ is silly move because as we see the driver was
> > never assumed to work with big page sizes (besides unsigned short type
> > here, PAGE_SHIFT and PAGE_MASK in the original code was as is and on ARM64
> > they compiled to 0 values w/o warnings, effectively make the driver
> > improperly functioning anyway).
>
> Apologies for the late answer.
>
> I think I'd favour the first option. It's not really useful to be able to
> compile this elsewhere; as such the driver doesn't do anything special that
> would make it prone to breakage through changes elsewhere.
>
> Would you like to send a patch? :-)
Done.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-12-14 15:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-21 8:23 drivers/media/pci/intel/ipu3/ipu3-cio2.c:163:56: warning: implicit conversion from 'unsigned long' to 'u16' (aka 'unsigned short') changes value from 131072 to 0 kernel test robot
2020-11-21 8:23 ` kernel test robot
2020-11-23 10:40 ` Andy Shevchenko
2020-11-23 10:40 ` Andy Shevchenko
2020-12-11 16:56 ` Sakari Ailus
2020-12-11 16:56 ` Sakari Ailus
2020-12-14 15:29 ` Andy Shevchenko [this message]
2020-12-14 15:29 ` Andy Shevchenko
2021-01-04 23:16 kernel test robot
2021-01-04 23:16 ` kernel test robot
2021-01-04 23:24 ` Sakari Ailus
2021-01-04 23:24 ` Sakari Ailus
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