如何在Yocto生成的initramfs镜像中实现initramfs-tools功能

Since you can't use Debian's initramfs-tools on your ARMv6 Yocto setup, let's break down how to replicate each of your required steps using Yocto's built-in initramfs-framework-base:

1. Add an init-top Script to Load SPI Modules #

Yocto's initramfs framework uses script directories similar to initramfs-tools. You'll need to create a custom script and package it into the initramfs:

Step 1: Create the SPI init-top script #

Create a file named spi in recipes-core/initramfs-spi-setup/files/init-top/ with this content:

#!/bin/sh
PREREQ=""

prereqs() {
    echo "$PREREQ"
}

case "$1" in
    prereqs)
        prereqs
        exit 0
        ;;
esac

# Load your SPI modules here (replace with your actual modules)
modprobe spi-bcm2835
modprobe spidev

Make the script executable:

chmod +x recipes-core/initramfs-spi-setup/files/init-top/spi

Step 2: Create a recipe to package this script #

Create recipes-core/initramfs-spi-setup/initramfs-spi-setup.bb:

SUMMARY = "SPI setup script for initramfs"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

SRC_URI = "file://init-top/spi"

S = "${WORKDIR}"

do_install() {
    install -d ${D}/usr/share/initramfs-tools/scripts/init-top
    install -m 0755 ${WORKDIR}/spi ${D}/usr/share/initramfs-tools/scripts/init-top/
}

FILES_${PN} = "/usr/share/initramfs-tools/scripts/init-top/spi"

# Ensure this is included in the initramfs
IMAGE_INSTALL_append = " initramfs-spi-setup"

2. Add Modules to be Loaded by the Module Daemon #

Instead of /etc/initramfs-tools/modules, Yocto uses modules-load.d configuration files to specify auto-loaded modules:

Step 1: Create a modules-load configuration file #

Create recipes-core/initramfs-module-config/files/spi-modules.conf with:

# List your modules here, one per line
spi-bcm2835
spidev

Step 2: Create a recipe for this config #

Create recipes-core/initramfs-module-config/initramfs-module-config.bb:

SUMMARY = "Module load config for initramfs"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

SRC_URI = "file://spi-modules.conf"

S = "${WORKDIR}"

do_install() {
    install -d ${D}/etc/modules-load.d
    install -m 0644 ${WORKDIR}/spi-modules.conf ${D}/etc/modules-load.d/
}

FILES_${PN} = "/etc/modules-load.d/spi-modules.conf"

IMAGE_INSTALL_append = " initramfs-module-config"

3. Set the FRAMEBUFFER Environment Variable #

To set FRAMEBUFFER=/dev/fb1 for Plymouth, add this to an initramfs startup script:

Step 1: Create a framebuffer setup script #

Create recipes-core/initramfs-fb-setup/files/init-bottom/fb1 with:

#!/bin/sh
PREREQ=""

prereqs() {
    echo "$PREREQ"
}

case "$1" in
    prereqs)
        prereqs
        exit 0
        ;;
esac

# Export the framebuffer variable for Plymouth
export FRAMEBUFFER=/dev/fb1
# Persist the variable for post-initramfs use
echo 'export FRAMEBUFFER=/dev/fb1' > ${ROOTFS}/etc/profile.d/fb1.sh

Make it executable:

chmod +x recipes-core/initramfs-fb-setup/files/init-bottom/fb1

Step 2: Create the recipe #

Create recipes-core/initramfs-fb-setup/initramfs-fb-setup.bb:

SUMMARY = "Framebuffer setup script for initramfs"
LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

SRC_URI = "file://init-bottom/fb1"

S = "${WORKDIR}"

do_install() {
    install -d ${D}/usr/share/initramfs-tools/scripts/init-bottom
    install -m 0755 ${WORKDIR}/fb1 ${D}/usr/share/initramfs-tools/scripts/init-bottom/
    
    # Install profile script to persist the variable
    install -d ${D}/etc/profile.d
    echo 'export FRAMEBUFFER=/dev/fb1' > ${D}/etc/profile.d/fb1.sh
    chmod 0644 ${D}/etc/profile.d/fb1.sh
}

FILES_${PN} = " \
    /usr/share/initramfs-tools/scripts/init-bottom/fb1 \
    /etc/profile.d/fb1.sh \
"

IMAGE_INSTALL_append = " initramfs-fb-setup"

Update Your Existing Image Recipe #

Modify your rpi-basic-image.bb to include these new packages:

include recipes-core/images/rpi-basic-image.bb

BASEPACKS = " \
    base-passwd \
    busybox \
    initramfs-live-boot \
    initramfs-framework-base \
    udev \
    ${ROOTFS_BOOTSTRAP_INSTALL} \
"

IMAGE_INSTALL = " \
    ${BASEPACKS} \
    plymouth plymouth-set-default-theme \
    initramfs-spi-setup \
    initramfs-module-config \
    initramfs-fb-setup \
"

# Do not pollute the initrd image with rootfs features
IMAGE_FEATURES = "splash"
SPLASH = "plymouth"
IMAGE_LINGUAS = ""
LICENSE = "MIT"
IMAGE_FSTYPES = "${INITRAMFS_FSTYPES}"
IMAGE_ROOTFS_SIZE = "8192"
IMAGE_OVERHEAD_FACTOR = "1.0"
IMAGE_ROOTFS_EXTRA_SPACE = "0"
IMAGE_ROOTFS_MAXSIZE = "12288"

CMDLINE_append = " quiet splash nomodeset plymouth.ignore-serial-consoles consoleblank=0 fbcon=map:1"
# Add fbcon=map:1 to ensure console uses fb1 if needed

BAD_RECOMMENDATIONS += "busybox-syslog"

Key Notes for ARMv6/U-boot #

• Double-check that your kernel config enables the required SPI and framebuffer modules for ARMv6.
• For debugging, add ls /dev/fb* to your framebuffer setup script to confirm /dev/fb1 exists in the initramfs.
• Ensure U-boot correctly passes your modified kernel command line to the kernel.

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