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掌機 - Miyoo Mini Flip - 修改開機流程

司徒打算將Miyoo Mini Flip的架構設計成跟小志掌機一樣，將Kernel、DTB都放在MicroSD前16MB磁區裡面，然後統一使用mininit去掛載rootfs.squashfs並且執行/sbin/init，如下圖所示：

首先修改U-Boot啟動參數，從MicroSD磁區載入Kernel和DTB檔案，為了可以節省開機時間，司徒不打算使用XZ壓縮格式，取而代之，司徒打算使用uImage格式，U-Boot啟動參數修改方式如下：

$ cp spi_1001-79B9.bin spi_uboot_load_uimage.bin
$ python3 ./update.py spi_uboot_load_uimage.bin env.txt 
    Environment variables : 19
    Environment size      : 0x375
    Environment area      : 0x5f004 ~ 0x60000
    CRC position          : 0x5f000
    CRC32                 : 0xc98bf04e

update.py

import sys
import struct
 
FILE = sys.argv[1]
ENV_FILE = sys.argv[2]
 
CRC_POS   = 0x5f000
CRC_START = 0x5f004
CRC_END   = 0x60000
 
def crc32b(data):
    crc = 0xffffffff
 
    for byte in data:
        crc ^= byte
 
        for _ in range(8):
            mask = -(crc & 1)
            crc = (crc >> 1) ^ (0xedb88320 & mask)
 
    return (~crc) & 0xffffffff
 
with open(ENV_FILE, "r", encoding="utf-8") as f:
    lines = []
 
    for line in f:
        line = line.rstrip("\r\n")
 
        if not line:
            continue
 
        lines.append(line.encode("utf-8"))
 
env_data = b"\0".join(lines) + b"\0\0"
env_size = CRC_END - CRC_START
 
if len(env_data) > env_size:
    print(
        f"ERROR: environment too large: "
        f"0x{len(env_data):x} bytes, "
        f"maximum 0x{env_size:x} bytes"
    )
    sys.exit(1)
 
with open(FILE, "r+b") as f:
    f.seek(CRC_START)
    f.write(b"\xff" * env_size)
    f.seek(CRC_START)
    f.write(env_data)
    f.seek(CRC_START)
    data = f.read(env_size)
 
    if len(data) != env_size:
        raise RuntimeError("Failed to read CRC area")
 
    crc = crc32b(data)
    f.seek(CRC_POS)
    f.write(struct.pack("<I", crc))
 
print(f"Environment variables : {len(lines)}")
print(f"Environment size      : 0x{len(env_data):x}")
print(f"Environment area      : 0x{CRC_START:05x} ~ 0x{CRC_END:05x}")
print(f"CRC position          : 0x{CRC_POS:05x}")
print(f"CRC32                 : 0x{crc:08x}")

env.txt

SdUpgradeImage=
baudrate=115200
bootargs=
bootcmd=gpio output 73 1;sleepms 50;gpio output 73 0;sleepms 150;gpio output 73 1;sleepms 200;gpio output 85 1;bootlogo 0 0 0 0 0;mw 1f001cc0 11;gpio out 8 0;mmc dev 0;mmc read 0x22000000 0x320 0x4000;mmc read 0x23000000 0x258 0x80;bootm 0x22000000 - 0x23000000
bootdelay=0
cpu_part_start=14270000
dispout=LCD752560
ethact=sstar_emac
ethaddr=00:30:1b:ba:02:db
filesize=1e4f0
miyoo_version=202510011046
sf_kernel_size=200000
sf_kernel_start=60000
sf_part_size=20000
sf_part_start=270000
stderr=serial
stdin=serial
stdout=serial
usb_folder=images

司徒建立一個暫時Repo (https://github.com/steward-fu/mmf)，最後將會Archive到https://github.com/steward-fu/website/releases/tag/miyoo-mini-flip，編譯Kernel、mininit步驟如下：

$ cd
$ wget https://github.com/steward-fu/website/releases/download/miyoo-mini-flip/ssd202d_toolchain.tar.gz
$ tar xvf ssd202d_toolchain.tar.gz
$ sudo mv ssd202d /opt

$ git clone https://github.com/steward-fu/mmf
$ cd kernel
$ vim scripts/dtc/dtc-lexer.lex.c +640
    extern YYLTYPE yylloc;

$ vim arch/arm/boot/dts/mmf.dts
    bootargs = "console=ttyS0,115200 console=tty ignore_loglevel loglevel=8 root=/dev/mmcblk0p1 rootwait rootfstype=vfat rw init=/mininit-syspart LX_MEM=0x7f00000 mma_heap=mma_heap_name0,miu=0,sz=0x1500000 mma_memblock_remove=1 highres=off mmap_reserved=fb,miu=0,sz=0x300000,max_start_off=0x7C00000,max_end_off=0x7F00000";

$ export PATH=/opt/ssd202d/bin:$PATH
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make distclean
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make mmf_defconfig
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- LOADADDR=0x22000000 make uImage modules -j4
$ sudo dd if=arch/arm/boot/uImage of=/dev/sdX bs=1024 seek=400
$ sudo dd if=arch/arm/boot/dts/mmf.dtb of=/dev/sdX bs=1024 seek=300

$ cd ../mininit
$ make
$ file mininit-syspart 
    mininit-syspart: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), statically linked, for GNU/Linux 3.2.0, stripped

編譯buildroot

$ cd
$ wget https://buildroot.org/downloads/buildroot-2026.08.tar.gz
$ tar xvf buildroot-2026.08.tar.gz
$ cd buildroot-2026.08
$ make menuconfig

ARM cortex-A7

glibc、C++

/opt/mmf

Welcome to MMF

squashfs

編譯

$ make

$ mkdir output/target/boot
$ make
$ file output/images/rootfs.squashfs 
    output/images/rootfs.squashfs: Squashfs filesystem, little endian, version 4.0, zlib compressed, 2901998 bytes, 388 inodes, blocksize: 131072 bytes, created: Sun Sep 27 13:11:47 2026

MicroSD格式(如果重新格式化，記得重新複製uImage、DTB)

MicroSD資料

重新燒錄SPI Image(spi_uboot_load_uimage.bin)後，在將MicroSD插入開機，就可以從UART看到如下Log:

mininit: mininit 2.0.2
mininit: free loop device: 0
mininit: setting up loop: 'rootfs.squashfs' via '/dev/loop0'
mininit: mounting 'rootfs.squashfs' on '/root'
mininit: rootfs.squashfs mounted on /root
mininit: moving '/dev' mount
mininit: root switch done
mininit: init: /sbin/init
mininit: starting /sbin/init
mount: mounting /dev/loop0 on / failed: Permission denied
seedrng: can't create directory '/var/lib/seedrng': Read-only file system
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Starting network: OK
Starting crond: OK

Welcome to MMF
MMF login: root
#

P.S. 如果想測試，使用這個commit 843b5601

Steward

分享是一種喜悅、更是一種幸福

掌機 - Miyoo Mini Flip - 修改開機流程