Linux device_{register | unregister}()代码分析
参考内核5.x, 主要关注下资源释放。/**
* device_register - register a device with the system.
* @dev: pointer to the device structure
*
* This happens in two clean steps - initialize the device
* an...阅读全文
devfreq governor代码分析
参考内核5.x，代码路径是在drivers/devfreq/，devfreq的代码定义是：Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework for Non-CPU Devices。而CPU动态调频是drivers/cpufreq，devfreq是基于cpufreq而来。第一次引入这个特性描述： ...阅读全文
如何制作和挂载erofs格式vendor镜像
Android P环境，mkfs.erofs is required firstly. Let's build vendor.img with erofs format.build process for vendor with ext4看下vendor image with ext4过程：core/main.mk:1111:vendorimage: $(INSTALLE...阅读全文
erofs代码分析: on-disk inode layout
参考staging erofs，on-disk inode layout相关实现是erofs_fs.h + super.c + inode.c。data mappings先看文档介绍：- Metadata & data could be mixed by design;Different from other read-only file systems, an EROF...阅读全文
How to build mkfs.erofs for ARM64
mkfs.erofs is a user-space tool to create erofs filesystem images.erofs是华为为了增强安卓性能提出的自研文件系统，其内核文档提到用户态工具:The following git tree provides the file system user-spacetools under development ...阅读全文
如何测试cpufreq setpolicy driver
上一篇说过有个cpufreq setpolicy patch涉及验证，qemu intel_pstate是不行了，主要是不支持X86_FEATURE_HWP or X86_FEATURE_APERFMPERF，只能在物理机上测试了。我的本本是E40(一代i3)，用了有点久了也不支持，intel_pstate是for SandyBridge arch，Intel从二代 i3...阅读全文