Re: [PATCH 20/22] gpio: protect the pointer to gpio_chip in gpio_device with SRCU

[kernel test robot <lkp@xxxxxxxxx>]

Hi Bartosz,

kernel test robot noticed the following build warnings:

[auto build test WARNING on brgl/gpio/for-next]
[also build test WARNING on linus/master v6.8-rc2 next-20240130]
[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/Bartosz-Golaszewski/gpio-protect-the-list-of-GPIO-devices-with-SRCU/20240130-205537
base:   https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git gpio/for-next
patch link:    https://lore.kernel.org/r/20240130124828.14678-21-brgl%40bgdev.pl
patch subject: [PATCH 20/22] gpio: protect the pointer to gpio_chip in gpio_device with SRCU
config: x86_64-randconfig-122-20240131 (https://download.01.org/0day-ci/archive/20240131/202401311050.YNdm98Hv-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240131/202401311050.YNdm98Hv-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), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401311050.YNdm98Hv-lkp@xxxxxxxxx/

sparse warnings: (new ones prefixed by >>)
>> drivers/gpio/gpiolib.c:444:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:444:22: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:444:22: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:1103:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:1103:9: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:1103:9: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:1182:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:1182:22: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:1182:22: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:2970:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:2970:14: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:2970:14: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:3004:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:3004:22: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:3004:22: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:3585:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:3585:14: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:3585:14: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:4772:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:4772:14: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:4772:14: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c:4846:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.c:4846:14: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.c:4846:14: sparse:    struct gpio_chip *
   drivers/gpio/gpiolib.c: note: in included file:
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
   drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *

vim +444 drivers/gpio/gpiolib.c

   422	
   423	/*
   424	 * Convert a GPIO name to its descriptor
   425	 * Note that there is no guarantee that GPIO names are globally unique!
   426	 * Hence this function will return, if it exists, a reference to the first GPIO
   427	 * line found that matches the given name.
   428	 */
   429	static struct gpio_desc *gpio_name_to_desc(const char * const name)
   430	{
   431		struct gpio_device *gdev;
   432		struct gpio_desc *desc;
   433		struct gpio_chip *gc;
   434	
   435		if (!name)
   436			return NULL;
   437	
   438		guard(srcu)(&gpio_devices_srcu);
   439	
   440		list_for_each_entry_srcu(gdev, &gpio_devices, list,
   441					 srcu_read_lock_held(&gpio_devices_srcu)) {
   442			guard(srcu)(&gdev->srcu);
   443	
 > 444			gc = rcu_dereference(gdev->chip);
   445			if (!gc)
   446				continue;
   447	
   448			for_each_gpio_desc(gc, desc) {
   449				if (desc->name && !strcmp(desc->name, name))
   450					return desc;
   451			}
   452		}
   453	
   454		return NULL;
   455	}
   456	

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