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Message-ID: <b9040273-aca8-432a-83aa-b0d6b1b88529@kadam.mountain>
Date:   Thu, 3 Aug 2023 13:13:04 +0300
From:   Dan Carpenter <dan.carpenter@...aro.org>
To:     oe-kbuild@...ts.linux.dev,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Michael Walle <michael@...le.cc>, linux-kernel@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Daniel Golle <daniel@...rotopia.org>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: [PATCH v7 5/7] nvmem: core: Rework layouts to become platform
 devices

Hi Miquel,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Miquel-Raynal/nvmem-core-Create-all-cells-before-adding-the-nvmem-device/20230802-022331
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20230801182132.1058707-6-miquel.raynal%40bootlin.com
patch subject: [PATCH v7 5/7] nvmem: core: Rework layouts to become platform devices
config: x86_64-randconfig-m001-20230730 (https://download.01.org/0day-ci/archive/20230803/202308030002.DnSFOrMB-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce: (https://download.01.org/0day-ci/archive/20230803/202308030002.DnSFOrMB-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>
| Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
| Closes: https://lore.kernel.org/r/202308030002.DnSFOrMB-lkp@intel.com/

New smatch warnings:
drivers/nvmem/core.c:1003 nvmem_register() warn: 'layout_np' is an error pointer or valid
drivers/nvmem/core.c:2130 nvmem_try_loading_layout_driver() warn: 'layout_np' is an error pointer or valid

Old smatch warnings:
drivers/nvmem/core.c:761 nvmem_add_cells_from_fixed_layout() warn: 'layout_np' is an error pointer or valid
drivers/nvmem/core.c:802 nvmem_layout_get() warn: 'layout_np' is an error pointer or valid

vim +/layout_np +1003 drivers/nvmem/core.c

266570f496b90d Michael Walle         2023-04-04  1000  
00d059fd6702f0 Miquel Raynal         2023-08-01  1001  	/* Populate layouts as devices */
00d059fd6702f0 Miquel Raynal         2023-08-01  1002  	layout_np = of_nvmem_layout_get_container(nvmem);
00d059fd6702f0 Miquel Raynal         2023-08-01 @1003  	if (layout_np) {

So, ugh, of_nvmem_layout_get_container() return NULL on error or error
pointer if either CONFIG_NVMEM or CONFIG_OF is turned off.  I feel like
that's a mistake.  Normally when a function returns both error pointers
and NULL then the NULL means the feature is disabled and the error
pointers mean there was an error.  Here it is the opposite.

I have written a blog about this:
https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/

At first I thought that this was to do with CONFIG_COMPILE_TEST but
actually that is disabled.  The issue here is that CONFIG_OF is turned
off.  So this is a genuine bug, we're compiling a module which will
always crash.

So I guess the fix is easy that this should return NULL if either
CONFIG_NVMEM or CONFIG_OF is turned off.  That was a long explanation
which is no longer required now that it's not a COMPILE_TEST issue.  :P

00d059fd6702f0 Miquel Raynal         2023-08-01  1004  		rval = of_platform_populate(nvmem->dev.of_node, NULL, NULL, NULL);
00d059fd6702f0 Miquel Raynal         2023-08-01  1005  		if (rval)
00d059fd6702f0 Miquel Raynal         2023-08-01  1006  			goto err_remove_cells;
00d059fd6702f0 Miquel Raynal         2023-08-01  1007  		of_node_put(layout_np);
00d059fd6702f0 Miquel Raynal         2023-08-01  1008  	}
00d059fd6702f0 Miquel Raynal         2023-08-01  1009  
25c9b5d3aa24a0 Miquel Raynal         2023-08-01  1010  	mutex_lock(&nvmem_devices_mutex);
25c9b5d3aa24a0 Miquel Raynal         2023-08-01  1011  	list_add_tail(&nvmem->node, &nvmem_devices_list);
25c9b5d3aa24a0 Miquel Raynal         2023-08-01  1012  	mutex_unlock(&nvmem_devices_mutex);
25c9b5d3aa24a0 Miquel Raynal         2023-08-01  1013  
f4853e1c321edb Bartosz Golaszewski   2019-02-15  1014  	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);
bee1138bea15a6 Bartosz Golaszewski   2018-09-21  1015  
eace75cfdcf7d9 Srinivas Kandagatla   2015-07-27  1016  	return nvmem;
3360acdf839170 Johan Hovold          2017-06-09  1017  
b985f4cba6dbb3 Bartosz Golaszewski   2018-09-21  1018  err_remove_cells:
b985f4cba6dbb3 Bartosz Golaszewski   2018-09-21  1019  	nvmem_device_remove_all_cells(nvmem);
fa72d847d68d78 Bartosz Golaszewski   2018-09-21  1020  	if (config->compat)
ae0c2d725512f3 Srinivas Kandagatla   2019-04-16  1021  		nvmem_sysfs_remove_compat(nvmem, config);
3360acdf839170 Johan Hovold          2017-06-09  1022  err_put_device:
3360acdf839170 Johan Hovold          2017-06-09  1023  	put_device(&nvmem->dev);
3360acdf839170 Johan Hovold          2017-06-09  1024  
b6c217ab9be689 Andrew Lunn           2016-02-26  1025  	return ERR_PTR(rval);
eace75cfdcf7d9 Srinivas Kandagatla   2015-07-27  1026  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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