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

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Date:   Fri, 4 Aug 2023 17:46:25 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     oe-kbuild@...ts.linux.dev,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        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>
Subject: Re: [PATCH v7 5/7] nvmem: core: Rework layouts to become platform
 devices

Hi again Dan,

miquel.raynal@...tlin.com wrote on Fri, 4 Aug 2023 17:39:03 +0200:

> Hi Dan,
> 
> dan.carpenter@...aro.org 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@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),
> 
> (Nice addition, a lot of newcomers would always add these tags
> otherwise.)
> 
> > 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/
> 
> 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.

Actually of_nvmem_layout_get_container() already returns NULL if
CONFIG_OF is not defined. This helper returns either a valid pointer of
NULL. Where can it return an error pointer?

> 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


Thanks,
Miquèl