嵌入式Linux下使用 Plymouth 實現開機畫面示例

By Toradex秦海

1). 簡介

嵌入式 Linux 下傳統實現 Splash Screen 的方式是通過替換 kernel 默認的 TUX 小企鵝 logo 為定制的開機畫面圖片來實現嵌入式設備開機圖片，雖然比較成熟且可以保證開機畫面加載比較早，但是存在的問題首先是對嵌入式設備不同顯示接口的兼容性不好，另外每次修改適配都需要重新編譯內核，維護起來不是很方便，然后就是只能支持靜態圖片無法支持動畫。基于上述原因，使用專門的 Splash Screen 工具來實現開機畫面逐漸成為嵌入式設備的主流方向，本文就簡單演示使用 Plymouth 工具來實現動態開機畫面的示例。

本文所演示的平臺來自于Toradex Verdin iMX8MM  嵌入式平臺，基于 NXP iMX8M Mini 系列 ARM 處理器，主要核心架構為 Cortex-A53 。

2). 硬件準備

a).  Verdin iMX8MM ARM 核心版配合 Dahlia 載板，并通過 DSI-LVDS Adapter 連接 10inch LVDS 液晶顯示屏以及調試串口以便測試。

3). 關于 Plymouth

a). Plymouth 是一個實現 Linux 啟動過程中開機畫面的工具軟件，其啟動的時間非常早，通過 initramfs 幫助可以在 Linux 內核加載同時啟動，甚至要早于 Linux rootfs 文件系統掛載。Plymouth 可以方便的實現開關機圖片或者動畫。

b). 關于 Plymouth 更多詳細介紹以及源代碼請自行參考如下資料。

./ Plymouth 官方頁面

Plymouth

./ Plymouth 源代碼

https://gitlab.freedesktop.org/plymouth/plymouth

./ Plymouth 深入配置使用說明

Plymouth - ArchWiki

4). 通過 Ycoto 環境配置 Plymouth 并編譯 Ycoto Linux BSP Image

a). 配置 Ycoto Project 編譯環境

./ 參考這里配置基本的 Ycoto Project 編譯環境

Build a Reference Image with Yocto Project/OpenEmbedded | Toradex Developer Center

./ 參考如下文章配置定制化 layer

通過Yocto Project定制嵌入式Yocto Linux鏡像

b). 在定制化 layer meta-customer-demos 下面添加 layer 配置文件

---------------------------------------

$ mkdir -p ../oe_core/layers/meta-customer-demos/conf

$ cd .../oe_core/layers/meta-customer-demos/conf

### create layer.conf file ###

# We have a conf and classes directory, append to BBPATH

BBPATH .= ":${LAYERDIR}"

# We have recipes-* directories, add to BBFILES

BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "customer-demos"

BBFILE_PATTERN_customer-demos = "^${LAYERDIR}/"

BBFILE_PRIORITY_customer-demos = "24"

# Let us add layer-specific bbappends which are only applied when that

# layer is included in our configuration

BBFILES += "${@' '.join('${LAYERDIR}/%s/recipes*/*/*.bbappend' % layer \

               for layer in BBFILE_COLLECTIONS.split())}"

# Add layer-specific bb files too

BBFILES += "${@' '.join('${LAYERDIR}/%s/recipes*/*/*.bb' % layer \

               for layer in BBFILE_COLLECTIONS.split())}"

LAYERDEPENDS_customer-demos = " \

    core \

    yocto \

    openembedded-layer gnome-layer multimedia-layer networking-layer \

"

LAYERSERIES_COMPAT_customer-demos = "hardknott honister kirkstone"

---------------------------------------

c). 在定制化 layer meta-customer-demos 下面添加 Plymouth 相關配置文件

./ 增加 Plymouth bb file

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/

$ mkdir -p recipes-core/plymouth

$ cd recipes-core/plymouth

### cteate plymouth_%.bbappend file ###

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

SRC_URI += " \
file://toradexlogo-white.png \
file://spinner.plymouth \
"

PACKAGECONFIG = "pango drm"

EXTRA_OECONF += "--with-udev --with-runtimedir=/run"

do_install:append () {
install -m 0644 ${WORKDIR}/toradexlogo-white.png ${D}${datadir}/plymouth/themes/spinner/watermark.png
install -m 0644 ${WORKDIR}/spinner.plymouth ${D}${datadir}/plymouth/themes/spinner/spinner.plymouth
}

---------------------------------------

./ 添加 Plymouth 使用的 theme 文件 和 background logo 圖片文件，這里使用的是一個配合屏幕分辨率的白色背景圖片，因此 spinner 圖標會被遮蓋，實際使用可以根據需要修改圖片文件和 theme 配置。

---------------------------------------

$ mkdir files

$ cp .../toradexlogo-white.png files

$ cd files

### cteate spinner theme file spinner.plymouth ###

[Plymouth Theme]

Name=Spinner

Description=Adoption of official Spinner Theme for Toradex.

ModuleName=two-step

[two-step]

Font=Cantarell 12

TitleFont=Cantarell Light 30

ImageDir=/usr/share/plymouth/themes/spinner

DialogHorizontalAlignment=.5

DialogVerticalAlignment=.382

TitleHorizontalAlignment=.5

TitleVerticalAlignment=.382

HorizontalAlignment=.5

VerticalAlignment=.7

WatermarkHorizontalAlignment=.5

WatermarkVerticalAlignment=.45

Transition=none

TransitionDuration=0.0

BackgroundStartColor=0x000000

BackgroundEndColor=0x000000

ProgressBarBackgroundColor=0x606060

ProgressBarForegroundColor=0xffffff

MessageBelowAnimation=true

---------------------------------------

d). 由于 Plymouth 是文件系統組件，通過 Linux kernel 加載完成后在使能systemd 來啟動，這樣就會導致比較大的延遲；為了盡可能使 Plymouth 在系統啟動過程中盡早啟動，可以添加包含 Plymouth 的 Initramfs 鏡像使得 Plymouth 在 Linux Kernel 加載過程中即同步啟動了。

./ 添加 Initramfs bb 定義以及相關文件，對應需要 files 目錄下的相關文件請參考這里

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/recipes-core

$ mkdir -p initramfs-framework/files

$ cd initramfs-framework

### cteate initramfs-framework_1.0.bbappend file ###

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

SRC_URI += "\

    file://plymouth \

    file://kmod \

    file://0001-Mount-run-with-tmpfs.patch \

    file://0002-only-scan-for-block-devices.patch \

"

PACKAGES:append = " \

    initramfs-module-plymouth \

    initramfs-module-kmod \

"

SUMMARY:initramfs-module-plymouth = "initramfs support for plymouth"

RDEPENDS:initramfs-module-plymouth = "${PN}-base plymouth ${@bb.utils.contains('DISTRO_FEATURES', 'systemd', 'systemd-udev-rules', '', d)}"

FILES:initramfs-module-plymouth = "/init.d/02-plymouth"

SUMMARY:initramfs-module-kmod = "initramfs support for loading kernel modules"

RDEPENDS:initramfs-module-kmod = "${PN}-base"

FILES:initramfs-module-kmod = "\

    /init.d/01-kmod \

    /etc/modules-load.d/* \

"

do_install:append() {

    install -m 0755 ${WORKDIR}/plymouth ${D}/init.d/02-plymouth

    install -m 0755 ${WORKDIR}/kmod ${D}/init.d/01-kmod

}

# Adding modules so plymouth can show the splash screen during boot

SRC_URI:append:mx8-nxp-bsp = " file://50-imx8-graphics.conf"

RDEPENDS:initramfs-module-kmod:append:mx8-nxp-bsp = " \

    kernel-module-display-connector \

    kernel-module-lontium-lt8912b \

"

do_install:append:mx8-nxp-bsp() {

    install -d ${D}/etc/modules-load.d/

    install -m 0755 ${WORKDIR}/50-imx8-graphics.conf ${D}/etc/modules-load.d/50-imx8-graphics.conf

}

---------------------------------------

./ 添加 initramfs image 定義文件

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/recipes-core

$ mkdir images

$ cd images

### cteate initramfs-plymouth-splash-image.bb file ###

DESCRIPTION = "Toradex plymouth splash demo initramfs image"

PACKAGE_INSTALL = "initramfs-framework-base initramfs-module-udev \

    initramfs-module-rootfs initramfs-module-debug \

    initramfs-module-plymouth ${VIRTUAL-RUNTIME_base-utils} base-passwd \

    initramfs-module-kmod"

SYSTEMD_DEFAULT_TARGET = "initrd.target"

# Do not pollute the initrd image with rootfs features

IMAGE_FEATURES = "splash"

export IMAGE_BASENAME = "initramfs-plymouth-splash-image"

IMAGE_LINGUAS = ""

LICENSE = "MIT"

IMAGE_FSTYPES = "cpio.gz"

IMAGE_FSTYPES:remove = "wic wic.gz wic.bmap wic.vmdk wic.vdi ext4 ext4.gz teziimg"

IMAGE_CLASSES:remove = "image_type_torizon image_types_ostree image_types_ota image_repo_manifest license_image qemuboot"

# avoid circular dependencies

EXTRA_IMAGEDEPENDS = ""

inherit core-image nopackages

IMAGE_ROOTFS_SIZE = "8192"

# Users will often ask for extra space in their rootfs by setting this

# globally.  Since this is a initramfs, we don't want to make it bigger

IMAGE_ROOTFS_EXTRA_SPACE = "0"

IMAGE_OVERHEAD_FACTOR = "1.0"

BAD_RECOMMENDATIONS += "busybox-syslog"

---------------------------------------

e). 由于增加了 initramfs image，就需要修改 distroboot 啟動文件 boot.scr 來調整啟動進程，這里通過修改 u-boot-distro-boot 文件來適配，對應的 files 目錄下的文件完整內容請參考這里

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/

$ mkdir -p recipes-bsp/u-boot/files

$ cd recipes-bsp/u-boot

### cteate u-boot-distro-boot.bbappend file ###

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

SRC_URI:append = " \

  file://boot.cmd.in \

"

---------------------------------------

f). 另外，對于 Verdin iMX8M Mini，由于顯示部分是通過 DSI-LVDS Bridge 來實現的，為了使得在 initramfs 階段就可以加載相關驅動，需要修改 Linux Kernel 配置，而對于其他 iMX8/iMX8X/iMX8MP 如果是原生 LVDS/HDMI 接口則無需修改。

---------------------------------------

$ cd .../oe_core/layers/meta-customer-demos/

$ mkdir -p recipes-kernel/linux/files

$ cd recipes-kernel/linux

### cteate linux-toradex%.bbappend file ###

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"

# Prevent the use of in-tree defconfig

unset KBUILD_DEFCONFIG

SRC_URI += "\

    file://defconfig \

    "

---------------------------------------

./ files 目錄下的完整 defconfig 文件請見這里，主要修改了如下幾個驅動的配置

---------------------------------------

-CONFIG_DRM_PANEL_LVDS=m

+CONFIG_DRM_PANEL_LVDS=y

-CONFIG_DRM_SEC_MIPI_DSIM=m

+CONFIG_DRM_SEC_MIPI_DSIM=y

-CONFIG_DRM_TI_SN65DSI83=m

+CONFIG_DRM_TI_SN65DSI83=y

-CONFIG_DRM_IMX_SEC_DSIM=m

+CONFIG_DRM_IMX_SEC_DSIM=y

---------------------------------------

g). 最后配置完成的 meta-customer-demos 文件結構如下

---------------------------------------

$ tree meta-customer-demos/

meta-customer-demos/

├── conf

│   └── layer.conf

├── recipes-bsp

│   └── u-boot

│       ├── files

│       │   └── boot.cmd.in

│       └── u-boot-distro-boot.bbappend

├── recipes-core

│   ├── images

│   │   ├── initramfs-ostree-torizon-image.bb

│   │   └── initramfs-plymouth-splash-image.bb

│   ├── initramfs-framework

│   │   ├── files

│   │   │   ├── 0001-Mount-run-with-tmpfs.patch

│   │   │   ├── 0002-only-scan-for-block-devices.patch

│   │   │   ├── 50-imx8-graphics.conf

│   │   │   ├── kmod

│   │   │   ├── plymouth

│   │   │   └── rootfs

│   │   └── initramfs-framework_1.0.bbappend

│   └── plymouth

│       ├── files

│       │   ├── spinner.plymouth

│       │   └── toradexlogo-white.png

│       └── plymouth_%.bbappend

└── recipes-kernel

    └── linux

        ├── files

        │   └── defconfig

        └── linux-toradex%.bbappend

13 directories, 17 files

---------------------------------------

h). 為了將 initramfs 集成到編譯生成的 Image 壓縮包內，需要修改如下 image_type 配置文件

---------------------------------------

--- a/layers/meta-toradex-bsp-common/classes/image_type_tezi.bbclass

+++ b/layers/meta-toradex-bsp-common/classes/image_type_tezi.bbclass

@@ -8,7 +8,7 @@

 WKS_FILE_DEPENDS:append = " tezi-metadata virtual/dtb"

 DEPENDS += "${WKS_FILE_DEPENDS}"

 IMAGE_BOOT_FILES_REMOVE = "${@make_dtb_boot_files(d) if d.getVar('KERNEL_IMAGETYPE') == 'fitImage' else ''}"

-IMAGE_BOOT_FILES:append = " overlays.txt ${@'' if d.getVar('KERNEL_IMAGETYPE') == 'fitImage' else 'overlays/*;overlays/'}"

+IMAGE_BOOT_FILES:append = " overlays.txt initramfs-plymouth-splash-image-${MACHINE}.cpio.gz;initramfs-plymouth-splash-image.img ${@'' if d.getVar('KERNEL_IMAGETYPE') == 'fitImage' else 'overlays/*;overlays/'}"

 IMAGE_BOOT_FILES:remove = "${IMAGE_BOOT_FILES_REMOVE}"

 RM_WORK_EXCLUDE += "${PN}"

---------------------------------------

i). 修改 build/conf/bblayer.conf 文件添加相關 layer

---------------------------------------

--- a/build/conf/bblayers.conf  2023-03-30 11:13:22.946533642 +0800

+++ b/build/conf/bblayers.conf 2023-11-17 16:03:01.666129480 +0800

@@ -35,6 +35,7 @@

   ${TOPDIR}/../layers/meta-freescale-distro \

   ${TOPDIR}/../layers/meta-toradex-demos \

   ${TOPDIR}/../layers/meta-qt5 \

+  ${TOPDIR}/../layers/meta-customer-demos \

   \

   \

   ${TOPDIR}/../layers/meta-toradex-distro \

---------------------------------------

j). 修改 build/conf/local.conf 文件，增加 Plymouth 和 initramfs 相關定義

---------------------------------------

# add plymouth support

CORE_IMAGE_EXTRA_INSTALL += "plymouth"

INITRAMFS_IMAGE = "initramfs-plymouth-splash-image"

INITRAMFS_FSTYPES = "cpio.gz"

---------------------------------------

k). 重新編譯生成 Ycoto Linux BSP Image

---------------------------------------

$ MACHINE="verdin-imx8mm" PARALLEL_MAKE="-j 4" BB_NUMBER_THREADS="4" bitbake tdx-reference-multimedia-image

---------------------------------------

l). 參考這里的說明將上述修改下重新編譯生成的 Ycoto Linux Image 通過 Toradex Easy Installer 更新到 Verdin iMX8MM 模塊。

5). Plymouth Splash 部署測試

a). 安裝好上述編譯的 Image 后，參考這里說明配置合適的 Device-tree Overlay 文件來適配屏幕；然后配置如下 U-boot 環境變量來顯示 Splash，且縮短加載時間

---------------------------------------

# setenv tdxargs ‘quiet logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles splash fbcon=map:3’

# setenv bootdelay 0

# saveenv && reset

---------------------------------------

b). 為了保證 Plymouth Splash和 Qt Demo App切換更自然，且中間不會被 Weston Desktop 中斷，需要修改一下一些 Systemd Service 文件

---------------------------------------

--- a/lib/systemd/system/plymouth-quit.service

+++ b/lib/systemd/system/plymouth-quit.service

@@ -1,6 +1,6 @@

 [Unit]

 Description=Terminate Plymouth Boot Screen

-After=rc-local.service plymouth-start.service systemd-user-sessions.service

+After=rc-local.service plymouth-start.service systemd-user-sessions.service waylan

d-app-launch.service

 [Service]

 ExecStart=-/bin/plymouth quit --retain-splash

--- a/lib/systemd/system/serial-getty@.service

+++ b/lib/systemd/system/serial-getty@.service

@@ -12,7 +12,7 @@

 Documentation=man:agetty(8) man:systemd-getty-generator(8)

 Documentation=http://0pointer.de/blog/projects/serial-console.html

 BindsTo=dev-%i.device

-After=dev-%i.device systemd-user-sessions.service plymouth-quit-wait.service getty

-pre.target

+After=dev-%i.device systemd-user-sessions.service getty-pre.target

 After=rc-local.service

 # If additional gettys are spawned during boot then we should make

--- a/lib/systemd/system/weston.service

+++ b/lib/systemd/system/weston.service

@@ -13,7 +13,7 @@

 After=systemd-user-sessions.service

 # If Plymouth is used, we want to start when it is on its way out.

-After=plymouth-quit-wait.service

+#After=plymouth-quit-wait.service

 # D-Bus is necessary for contacting logind. Logind is required.

 Wants=dbus.socket

--- a/etc/xdg/weston/weston.ini

+++ b/etc/xdg/weston/weston.ini

@@ -6,6 +6,7 @@

 repaint-window=16

 #enable-overlay-view=1

 modules=screen-share.so

+shell=kiosk-shell.so

 #[shell]

 #size=1920x1080

---------------------------------------

b). 最后部署完成的測試效果如下，實測從開機到出現 Splash 畫面大約5秒，另外 Plymouth splash 默認除了支持開機畫面，在 reboot 重啟和 poweroff 關機的時候也會同樣顯示 splash 畫面

動畫演示如下

6). 總結

本文基于嵌入式 Linux 簡單演示了 Plymouth splash 開機畫面的部署和測試。