On Sat, May 05, 2018 at 12:22:29AM +0200, Lucas Magasweran wrote: > Hi Jean and al, > > Thank you for your Kernel Recipes 2016 talk about the new hwmon > registration API [1]. > > I'm trying to use the latest hwmon_device_register_with_info() API > where hwmon core handles the sysfs attributes for me. However, I cannot > use it with a NULL parent struct device *dev and non-NULL struct > hwmon_chip_info *chip. My platform driver module_init() calls > hwmon_device_register_with_info(). __hwmon_device_register() has a NULL > pointer dereference error because it uses device managed memory > allocation internally. > > For example, > > my_hwmon_dev = hwmon_device_register_with_info(NULL, "my_name", NULL, > &my_hwmon_chip_info, > NULL); > --> __hwmon_device_register(NULL, "my_name", NULL, > &my_hwmon_chip_info, NULL); > ----> hwdev->groups = devm_kcalloc(NULL, ngroups, > sizeof(*groups), GFP_KERNEL); > > I see that later in the function dev is checked for NULL in "hdev- > >of_node = dev ? dev->of_node : NULL;" but it cannot be NULL for > devm_kcalloc(). > > I tried the following 4.10.17 patch because I expected the hwmon > attributes to be stored with the hwmon device directly and not the > struct device *dev parent. However, none of my attributes are showing > up in /sys/class/hwmon#/. > I assume you mean /sys/class/hwmon/hwmon#/. > Is my approach wrong? > Yes. Parent must not be NULL if chip is used. The use case of parent==NULL and chip!=NULL is not and will not be supported. Also, the only reason for supporting a NULL parent is that the thermal code uses it, and it is all but impossible to change the thermal code to provide a device pointer. I would strongly suggest to modify your code and provide a parent (a pointer to either a platform or hardware device). Most likely that means to convert it to a platform device. If you insist in not providing a parent, you'll have to use hwmon_device_register_with_groups(). Of course, that means you'll have to handle the attributes. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
