Re: [PATCH 3/5] iio: mcp9600: Recognize chip id for mcp9601

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Mon, 18 Aug 2025 08:06:59 -0700
Nathan Chancellor <nathan@kernel.org> wrote:

> Hi Jonathan,
> 
> On Sat, Aug 16, 2025 at 11:02:43AM +0100, Jonathan Cameron wrote:
> > On Sat, 16 Aug 2025 16:46:12 +0800
> > kernel test robot <lkp@intel.com> wrote:
> >   
> > > Hi Ben,
> > > 
> > > kernel test robot noticed the following build warnings:
> > > 
> > > [auto build test WARNING on jic23-iio/togreg]
> > > [also build test WARNING on linus/master v6.17-rc1 next-20250815]
> > > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > > And when submitting patch, we suggest to use '--base' as documented in
> > > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > > 
> > > url:    https://github.com/intel-lab-lkp/linux/commits/Ben-Collins/dt-bindings-iio-mcp9600-Add-compatible-for-microchip-mcp9601/20250816-005705
> > > base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
> > > patch link:    https://lore.kernel.org/r/20250815164627.22002-4-bcollins%40watter.com
> > > patch subject: [PATCH 3/5] iio: mcp9600: Recognize chip id for mcp9601
> > > config: riscv-randconfig-001-20250816 (https://download.01.org/0day-ci/archive/20250816/202508161646.PDl6V4EU-lkp@intel.com/config)
> > > compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 93d24b6b7b148c47a2fa228a4ef31524fa1d9f3f)
> > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250816/202508161646.PDl6V4EU-lkp@intel.com/reproduce)
> > > 
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202508161646.PDl6V4EU-lkp@intel.com/
> > > 
> > > All warnings (new ones prefixed by >>):  
> 
> <trim unrelated -Wnull-pointer-arithmetic>
> 
> > > >> drivers/iio/temperature/mcp9600.c:440:53: warning: invalid conversion specifier '\x0a' [-Wformat-invalid-specifier]    
> > >      440 |                                 "Expected id %02x, but device responded with %02\n",
> > >          |                                                                              ~~~^
> > >    include/linux/dev_printk.h:156:62: note: expanded from macro 'dev_warn'
> > >      156 |         dev_printk_index_wrap(_dev_warn, KERN_WARNING, dev, dev_fmt(fmt), ##__VA_ARGS__)
> > >          |                                                                     ^~~
> > >    include/linux/dev_printk.h:19:22: note: expanded from macro 'dev_fmt'
> > >       19 | #define dev_fmt(fmt) fmt
> > >          |                      ^~~
> > >    include/linux/dev_printk.h:110:16: note: expanded from macro 'dev_printk_index_wrap'
> > >      110 |                 _p_func(dev, fmt, ##__VA_ARGS__);                       \
> > >          |                              ^~~  
> > > >> drivers/iio/temperature/mcp9600.c:441:26: warning: data argument not used by format string [-Wformat-extra-args]    
> > >      440 |                                 "Expected id %02x, but device responded with %02\n",
> > >          |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >      441 |                                  chip_info->chip_id, dev_id);
> > >          |                                                      ^
> > >    include/linux/dev_printk.h:156:70: note: expanded from macro 'dev_warn'
> > >      156 |         dev_printk_index_wrap(_dev_warn, KERN_WARNING, dev, dev_fmt(fmt), ##__VA_ARGS__)
> > >          |                                                                     ~~~     ^
> > >    include/linux/dev_printk.h:110:23: note: expanded from macro 'dev_printk_index_wrap'
> > >      110 |                 _p_func(dev, fmt, ##__VA_ARGS__);                       \
> > >          |                              ~~~    ^
> > >    drivers/iio/temperature/mcp9600.c:428:22: warning: unused variable 'ret' [-Wunused-variable]
> > >      428 |         int ch_sel, dev_id, ret;
> > >          |                             ^~~
> > >    10 warnings generated.
> > > 
> > > 
> > > vim +/x0a +440 drivers/iio/temperature/mcp9600.c
> > > 
> > >    422	
> > >    423	static int mcp9600_probe(struct i2c_client *client)
> > >    424	{
> > >    425		const struct mcp_chip_info *chip_info = i2c_get_match_data(client);  
> > 
> > Probably a false positive as I don't think we can probe without something matching and hence
> > that not being NULL but an error check on that match is still a nice to have and should
> > resolve this build warning.  Note there is very little chance a compiler could ever figure
> > out if this can be NULL or not so it's a reasonable warning!  
> 
> I am not sure I follow if you are referring to the -Wformat warnings
> above. Isn't it pointing out that the second specifier is missing the
> actual type? Shouldn't it be '%02x' or something of the sort?

I think I completely misread the report!  Sorry about that. Ignore my comment.

Jonathan

> 
> Cheers,
> Nathan
>