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

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Message-Id: <81628282-E80B-46BD-851E-6DCC48CCC953@watter.com>
Date: Mon, 18 Aug 2025 11:11:57 -0400
From: Ben Collins <bcollins@...ter.com>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Jonathan Cameron <jic23@...nel.org>,
 kernel test robot <lkp@...el.com>,
 David Lechner <dlechner@...libre.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>,
 llvm@...ts.linux.dev,
 oe-kbuild-all@...ts.linux.dev,
 linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] iio: mcp9600: Recognize chip id for mcp9601


> On Aug 18, 2025, at 11:06 AM, Nathan Chancellor <nathan@...nel.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@...el.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@...el.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?

That actually was the issue and has already been fixed in follow up.

Thanks