如何在Yocto构建的Raspberry Pi CM3系统启动时自动加载内核模块？

Hey there! Let's sort out that kernel module auto-loading problem for your Raspberry Pi CM3 Yocto build. Since you already have the modules sitting in /lib/modules on your target device, we’ve got a couple of reliable approaches to get them loading automatically on boot—plus we’ll fix those dependency headaches at the same time.

Method 1: Configure Auto-Loading in Your Yocto Recipe (Recommended, Fix at Build Time) #

If your drivers were added via a custom recipe or .bbappend, you can set this up directly in your Yocto build so the configuration ships with the image (no post-flash edits needed):

• For a single module:
  Add this line to your .bb or .bbappend file:

  MODULES_AUTOLOAD += "your-module-name"
  

  This variable tells Yocto to generate the necessary modprobe configs, which will auto-load the module on boot and handle dependencies automatically (modprobe is way smarter than insmod about resolving dependent modules).
• For multiple modules, just space-separate them:

  MODULES_AUTOLOAD += "module1 module2 module3"
  

• If your module needs load-time parameters, use MODULES_CONF to add a custom config:

  MODULES_CONF += "your-module.conf"
  

  Then create your-module.conf in your recipe's files directory with content like:

  options your-module-name param1=value1 param2=value2
  

  This ensures the parameters are applied automatically when the module loads.

Method 2: Manually Configure on the Target System (Great for Testing or Post-Flash Edits) #

If you don't want to rebuild your Yocto image, you can set this up directly on your Raspberry Pi CM3:

• First, stop using insmod—switch to modprobe your-module-name instead. It will automatically detect and load any dependent modules, which eliminates those dependency issues you were hitting.
• To set up auto-load on boot:
  1. Create or edit a file in /etc/modules-load.d/ (e.g., /etc/modules-load.d/my-drivers.conf), adding each module name on its own line:

     your-module-name
     another-dependent-module
     

     Systemd reads all configs in this directory on boot and uses modprobe to load the listed modules.
  2. For module parameters, create a file in /etc/modprobe.d/ (e.g., /etc/modprobe.d/my-driver.conf):

     options your-module-name param1=value1
     

• To verify your setup works:
  Use systemctl status systemd-modules-load.service to check the status of the module-loading service, or reboot and run lsmod | grep your-module-name to confirm the module is loaded.

Quick Notes to Avoid Headaches #

• Double-check that your module matches your kernel version: Run uname -r on the target, and make sure there's a matching directory in /lib/modules/ (modules are stored per kernel version).
• Ensure your Yocto kernel config has dynamic module support enabled (CONFIG_MODULES=y)—this is usually default in meta-raspberrypi, but it's worth confirming if you've tweaked kernel settings.
• If you built the module directly into the kernel (not as a dynamic module), you don't need to load it manually—it will be present on boot automatically. But since you're seeing it in /lib/modules, you're using dynamic modules, so the above methods apply.

内容的提问来源于stack exchange，提问作者Asma Maaroufi