Read squashfs readpage() code
内核参考5.x:const struct address_space_operations squashfs_aops = {
.readpage = squashfs_readpage
};static int squashfs_readpage(struct file *file, struct page *page)
{
...
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e-Paper Weather Station
I always want to use the 7.5 e-Paper(i already have) to display weather forecast instead of my previous solution displayed on LCD. You know, the old one is not beautiful for me any more s...阅读全文
erofs-utils mkfs 概览
参考erofs-utils 1.2.1, 入口是erofs_mkfs_build_tree(), 不关注xattr/extent, 看之前我们再了解下inode:Inodes store information about files and directories (folders), such as file ownership, access mode (read,...阅读全文
eMMC CMDQ 超时分析
先看HW架构CQE: Command Queueing Engine，负责管理software和eMMC device的data传输。首先CQE接收来自SW的task(via TDL和doorbell)，接下来的command flows主要有三步：Step1. Queuing a Transaction(CMD44+CMD45)CQE发出CMD44/CMD45给eMMC...阅读全文
UFS Write Booster 分析
先来看看JEDEC有关WriteBooster(WB)的描述：TLC NAND比SLC NAND慢的原因就是TLC里面有更多的programming steps。ok，为了提高性能，那就把TLC NAND的一部分配置成SLC NAND不就行了。rt，WriteBooster特性由此而来，就是把这部分SLC NAND用作WriteBooster Buffer。有个概率图： ...阅读全文
schedutil CPUFreq governor 代码分析
参考内核5.x, code是kernel/sched/cpufreq_schedutil.c，配置说明：config CPU_FREQ_GOV_SCHEDUTIL bool "'schedutil' cpufreq policy governor"
depends on CPU_FREQ && SMP
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