Yocto环境下如何添加树外设备驱动？

Hey there! Since you're new to Yocto and already have a working build environment for uboot+kernel+rootfs, let's break down how to integrate that bcmdhd driver properly—we'll take it step by step, no jargon overload.

1. Stick to Out-of-Tree Module Best Practices #

Your driver is built separately from the mainline kernel, so we'll create a dedicated Yocto recipe for it. This keeps your kernel source clean and aligns with Yocto's modular workflow.

2. Set Up Your Custom Layer (Recommended) #

First, create a custom layer to house your driver recipe—this avoids messing with Yocto's core layers:

• Make a directory like meta-my-drivers
• Add the standard layer structure inside:

  meta-my-drivers/
  ├── conf/
  │   └── layer.conf
  └── recipes-kernel/
      └── bcmdhd/
          ├── bcmdhd/
          │   └── [drop your full bcmdhd driver source here]
          └── bcmdhd_%.bb
  

Pro tip: If your driver lives in a git repo, you can use SRC_URI to pull it directly instead of copying files—we'll cover that in the recipe.

3. Write the BCMDHD Recipe (bcmdhd_%.bb) #

Here's a tailored recipe that mimics your native build command. Adjust placeholders to match your setup:

DESCRIPTION = "Broadcom BCMDHD WiFi Driver (BCM4359 PCIe)"
LICENSE = "Proprietary"
LIC_FILES_CHKSUM = "file://LICENSE;md5=[replace-with-actual-md5-of-your-license-file]"

# Use this if your driver is local, or swap for git://your-repo-url.git if using a repo
SRC_URI = "file://bcmdhd/"
S = "${WORKDIR}/bcmdhd"

# Pull in kernel build dependencies
DEPENDS = "virtual/kernel"
inherit module

# Pass your exact CONFIG flags to the make command
EXTRA_OEMAKE += " \
    CONFIG_BCMDHD_PCIE=y \
    CONFIG_BCMDHD=m \
    CONFIG_BCM4359=y \
"

# Install the module to the correct kernel module directory
do_install() {
    install -d ${D}${base_libdir}/modules/${KERNEL_VERSION}/kernel/drivers/net/wireless/
    install -m 0644 ${S}/bcmdhd.ko ${D}${base_libdir}/modules/${KERNEL_VERSION}/kernel/drivers/net/wireless/
}

# Ensure the module is included in your image and dependencies are met
FILES_${PN} += "${base_libdir}/modules/${KERNEL_VERSION}/kernel/drivers/net/wireless/bcmdhd.ko"
RDEPENDS_${PN} = "kernel-module-bcmdhd"

Key details:

• The inherit module line handles all the tedious stuff like pointing to the correct kernel build directory (no more manual -C or M= parameters!).
• EXTRA_OEMAKE injects your custom CONFIG flags directly into the build—exactly like your native make command.
• If your driver needs firmware files, add them via SRC_URI and install them to ${D}/lib/firmware/ in the do_install section.

4. Enable Your Layer and Recipe #

• Add your new layer to conf/bblayers.conf in your build directory:

  BBLAYERS += "${TOPDIR}/../meta-my-drivers"
  

• Add the driver to your image's package list in local.conf:

  IMAGE_INSTALL:append = " bcmdhd"
  

  Use IMAGE_INSTALL += " bcmdhd" if you're on an older Yocto version.

5. Build and Verify #

Run your build as usual:

bitbake your-target-image-name

Once the build finishes, flash the image to your target. Test if the module loads with:

modprobe bcmdhd
lsmod | grep bcmdhd

Quick Troubleshooting #

• Kernel version mismatch: Double-check that your Yocto kernel version matches what you used for native compilation. Use uname -r on the target or check KERNEL_VERSION in your build logs.
• Build errors: Check the detailed log at tmp/work/[your-target-arch]/bcmdhd/[version]/temp/log.do_compile—most issues are missing dependencies or typos in CONFIG flags.
• Firmware not found: If the driver complains about missing firmware, add those files to your recipe and install them to /lib/firmware/.

内容的提问来源于stack exchange，提问作者ZioByte