Re: [PATCH v7 5/7] nvmem: core: Rework layouts to become platform devices

[Miquel Raynal]

Hi Dan,

dan.carpenter@xxxxxxxxxx wrote on Thu, 3 Aug 2023 13:13:04 +0300:

> 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@xxxxxxxxx/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce: (https://download.01.org/0day-ci/archive/20230803/202308030002.DnSFOrMB-lkp@xxxxxxxxx/reproduce)
> 
> If you fix the issue in a separate patch/commit
> (i.e. not just a new version of the same patch/commit),

(Nice addition, a lot of newcomers would always add these tags
otherwise.)

> kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> | Closes: https://lore.kernel.org/r/202308030002.DnSFOrMB-lkp@xxxxxxxxx/
> 
> 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/

Nice (besides the huge spider which stared at me unexpectedly :-) )

> 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

I wanted to disable CONFIG_OF to make the test, I totally forget, I'll
handle this case and return NULL when this happens.

However I don't understand why you mention CONFIG_NVMEM, because if it
is not defined, this file will not compile at all?

> 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  }
> 


Thanks,
Miquèl