The below table provides a sub-list of sysfs APIs that can be used to provide data to user space from a kernel module. For a more comprehensive list – refer sysfs.h file in the specific Linux Kernel version that you are working with.
| Kernel API | Description |
| struct kobject *kobject_create_and_add(const char *name, struct kobject *parent) | This function creates a kobject structure dynamically and registers it with sysfs |
| void kobject_del(struct kobject *kobj) | Remove an object added using kobject_add or kobject_create_and_add |
| int sysfs_create_dir(struct kobject *kobj); | To create a directory in sysfs. The recent versions as of the day (Linux 5.14 has sysfs_create_dir_ns) accepts a custom namespace tag as a parameter |
| void sysfs_remove_dir(struct kobject *kobj); | To remove a directory in sysfs file system. |
| int sysfs_rename_dir(struct kobject *kobj. const char *new_name); | To rename a directory in sysfs. The recent versions as of the day (Linux 5.14 has sysfs_rename_dir_ns) accepts a custom namespace tag as a parameter |
| int sysfs_create_file(struct kobject *kobj, const struct attribute *attr) | Create a kobject attribute. The recent versions as of the day (Linux 5.14 has sysfs_create_file_ns) accepts a custom namespace tag as a parameter |
| void sysfs_remove_file(struct kobject *kobj, const struct attribute *attr) | Remove a file attribute. The recent versions as of the day (Linux 5.14 has sysfs_remove_file_ns) accepts a custom namespace tag as a parameter |
| int sysfs_create_group(struct kobject *kobj, const struct attribute_group *grp) | Similar to sysfs_create_file, but allows to create a group of attributes |
The Below code shows a sample implementation for Kernel 5.11.
The Makefile for the code is shown below
The output of the sysfs example code is shown below. Modifying the value in sysfs_exmpl requires the shell to be “root”.
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