查找register_chrdev()等设备驱动函数的GNU/Linux手册及相关信息

Great question! Let's break this down clearly so you can get the detailed documentation you need, and clear up the confusion about what these functions actually are.

一、获取详细man手册的正确方式 #

These functions are part of Linux's kernel-space character device driver API, so their proper documentation lives in the kernel API man pages (section 9). Here's how to access them:

• Local system man pages: First, install the kernel development documentation package for your distro:
  • On Debian/Ubuntu-based systems: Install linux-manpages-dev via sudo apt install linux-manpages-dev
  • On RHEL/CentOS/Fedora: Install kernel-doc via sudo dnf install kernel-doc
  • Once installed, you can pull up the full docs with terminal commands:

    man 9 register_chrdev
    man 9 alloc_chrdev_region
    

  These man pages will include all the details you're missing: function prototypes, required header files, return values, error codes, and usage notes.
• Kernel source code docs: If you don't want to install the man packages, you can check the Linux kernel source directly. The Documentation/ directory has extensive driver-focused guides, and the function definitions in <linux/fs.h> (where these APIs live) include detailed comments covering all the specifics you need.

二、Are these system calls? #

Short answer: No, they are not system calls.

• System calls are the standardized interfaces that user-space programs use to request kernel services (like open() or read(), documented in man section 2). They have a defined user-to-kernel transition mechanism, and any user-space app can call them.
• register_chrdev() and alloc_chrdev_region() are kernel-internal API functions. They're only meant to be called from kernel modules (i.e., device drivers) running in kernel space. There's no way for a user-space program to invoke them directly—they exist purely to help driver developers set up character devices properly.

Quick Reference for Key Details #

• Header file: Both functions are declared in <linux/fs.h>
• Return values & errors:
  • alloc_chrdev_region(): Returns 0 on success; on failure, returns a negative error code (e.g., -EINVAL for invalid parameters, -EBUSY if the requested device range is already in use)
  • register_chrdev() (an older API—modern drivers prefer alloc_chrdev_region() + cdev_init()): Returns the assigned major device number on success; returns a negative error code on failure (common ones include -EBUSY if the major number is already taken)

内容的提问来源于stack exchange，提问作者Dr. Essen