在为 Android 设备撰写 Device Tree 时不免会遇到分区大小的计算，这里我找到了一些简单的方法，记录下来避免以后踩坑。
首先是 BOARD_FLASH_BLOCK_SIZE，用 BOARD_KERNEL_PAGESIZE 的值乘以 64 即可
其次是众大多分区，我们可以用 dd of=/dev/null if=partition 命令来获取大小，但对于大分区来说耗时太长，而且需要root权限
转而一想，为什么不能扒 linux 分区表从而直接获取大小呢
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| sawshark:/ $ cat /proc/partitions
major minor
254 0 262144 zram0
179 0 3817472 mmcblk0
179 1 512 mmcblk0p1
179 2 512 mmcblk0p2
179 3 512 mmcblk0p3
179 4 512 mmcblk0p4
179 5 768 mmcblk0p5
179 6 768 mmcblk0p6
179 7 5120 mmcblk0p7
179 8 5120 mmcblk0p8
179 9 10240 mmcblk0p9
179 10 5120 mmcblk0p10
179 11 4096 mmcblk0p11
179 12 4096 mmcblk0p12
179 13 1 mmcblk0p13
179 14 8 mmcblk0p14
179 15 1024 mmcblk0p15
179 16 10240 mmcblk0p16
179 17 512 mmcblk0p17
179 18 512 mmcblk0p18
179 19 5120 mmcblk0p19
179 20 10240 mmcblk0p20
179 21 32 mmcblk0p21
179 22 4096 mmcblk0p22
179 23 4096 mmcblk0p23
179 24 256 mmcblk0p24
179 25 256 mmcblk0p25
179 26 256 mmcblk0p26
179 27 256 mmcblk0p27
179 28 10240 mmcblk0p28
179 29 32768 mmcblk0p29
179 30 16 mmcblk0p30
179 31 32768 mmcblk0p31
259 0 111568 mmcblk0p32
259 1 1048576 mmcblk0p33
259 2 65536 mmcblk0p34
259 3 2436564 mmcblk0p35
179 32 512 mmcblk0rpmb
253 0 1032176 dm-0
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blocks 为块设备总块数，每个块是 1024 字节，等同于 KB
name 就是 块设备名称 了，通过列目录可以很方便找到 可读名称 和 块设备名称 的关系
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| sawshark:/ $ ls -l /dev/block/bootdevice/by-name
total 0
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 DDR -> /dev/block/mmcblk0p21
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 aboot -> /dev/block/mmcblk0p7
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 abootbak -> /dev/block/mmcblk0p8
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 boot -> /dev/block/mmcblk0p29
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 cache -> /dev/block/mmcblk0p34
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 cmnlib -> /dev/block/mmcblk0p24
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 cmnlibbak -> /dev/block/mmcblk0p25
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 config -> /dev/block/mmcblk0p18
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 devinfo -> /dev/block/mmcblk0p23
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 fsc -> /dev/block/mmcblk0p13
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 fsg -> /dev/block/mmcblk0p22
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 keymaster -> /dev/block/mmcblk0p26
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 keymasterbak -> /dev/block/mmcblk0p27
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 keystore -> /dev/block/mmcblk0p17
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 misc -> /dev/block/mmcblk0p15
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 modem -> /dev/block/mmcblk0p32
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 modemst1 -> /dev/block/mmcblk0p11
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 modemst2 -> /dev/block/mmcblk0p12
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 nfc -> /dev/block/mmcblk0p19
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 nvbin -> /dev/block/mmcblk0p10
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 nvdata -> /dev/block/mmcblk0p9
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 oem -> /dev/block/mmcblk0p28
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 recovery -> /dev/block/mmcblk0p31
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 reserved -> /dev/block/mmcblk0p20
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 rpm -> /dev/block/mmcblk0p3
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 rpmbak -> /dev/block/mmcblk0p4
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 sbl1 -> /dev/block/mmcblk0p1
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 sbl1bak -> /dev/block/mmcblk0p2
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 sec -> /dev/block/mmcblk0p30
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 splash -> /dev/block/mmcblk0p16
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 ssd -> /dev/block/mmcblk0p14
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 system -> /dev/block/mmcblk0p33
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 tz -> /dev/block/mmcblk0p5
lrwxrwxrwx 1 root root 20 1970-01-13 18:59 tzbak -> /dev/block/mmcblk0p6
lrwxrwxrwx 1 root root 21 1970-01-13 18:59 userdata -> /dev/block/mmcblk0p35
|
综合以上，用awk套娃一个自动化脚本
安卓设备默认是不带awk的，所以需要通过电脑套娃
这里以wsl运行环境为例，如果不是wsl自行更改 call_cat 和 call_ls 两个变量即可
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| #!/bin/bash
call_cat="adb.exe shell cat"
call_ls="adb.exe shell ls"
name_base="/dev/block/bootdevice"
if [[ -n $1 ]]; then
block_name=$(${call_ls} -la ${name_base}/by-name/$1 2>/dev/null | awk -F " -> /dev/block/" '{print $2}')
if [[ -n ${block_name} ]]; then
${call_cat} /proc/partitions | grep ${block_name} | awk -F " " '{print $3 * 1024}'
else
echo "Error: partition $1 not found"
fi
else
echo "Usage: $0 [partition name]"
fi
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运行测试
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| mlgmxyysd@MlgmXyysd-NUC:~$ ./partitions.sh
Usage: ./partitions.sh [partition name]
mlgmxyysd@MlgmXyysd-NUC:~$ ./partitions.sh non_exist_partition
Error: partition non_exist_partition not found
mlgmxyysd@MlgmXyysd-NUC:~$ ./partitions.sh system
1073741824
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与上方输出计算结果一致，成功
更新：上面的方式在一些设备中可能会被SELinux挡掉
其实还有一种更简单的方式
重启设备至 fastboot 或 bootloader 模式
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| fastboot getvar partition-size:[partition name]
mlgmxyysd@MlgmXyysd-NUC:~$ fastboot.exe getvar partition-size:system
partition-size:system: 0x40000000
Finished. Total time: 0.116s
|
返回值转换为 DEC 为 1073741824 ，单位为 Byte
感谢：TH779
