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‎README.md‎

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NO.|文件名称|摘要
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:--:|:--|:--
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0013| [开机自动发IP信息邮件](docs/0013_开机自动发IP信息邮件.md) | Python3自动发邮件
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0012| [dtparam_dtoverlay_DTS动态设备树](docs/0012_dtparam_dtoverlay_DTS动态设备树.md) | 分析dtparam/dtoverlay本质，为什么能够动态改变设备与驱动的match
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0011| [SoC设备树DTS分析](docs/0011_SoC设备树DTS分析.md) | 怎么分析芯片设备树
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0010| [Tmux_Vim_Ctags_Cscope代码分析](docs/0010_Tmux_Vim_Ctags_Cscope代码分析.md) | 在Linux命令行如何阅读代码？
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0009| [USB摄像头搭建IP网络摄像头](docs/0009_USB摄像头搭建IP网络摄像头.md) | 使用USB Camera搭建IP Camera，理解IP Camera工作原理
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0008| [USB摄像头分析udev加载驱动原理](docs/0008_USB摄像头分析udev加载驱动原理.md) | 使用USB Camera分析udev加载驱动原理，理解udev工作原理
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0007| [Systemd进程启动](docs/0007_Systemd进程启动.md) | 分析Linux系统进程何启动起来
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0006| [搭建samba服务端](docs/0006_搭建samba服务端.md) | 像访问普通文件夹一样访问树莓派文件系统

‎docs/0009_USB摄像头搭建IP网络摄像头.md‎

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# USB摄像头搭建IP网络摄像头
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使用USB Camera搭建IP Camera，理解IP Camera工作原理
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## 参考文档
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* [利用flask将opencv实时视频流输出到浏览器](https://www.cnblogs.com/arkenstone/p/7159615.html)
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* [使用 multipart/x-mixed-replace 实现 http 实时视频流](https://segmentfault.com/a/1190000018563132)
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## 简述
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从USB摄像头获取视频帧(一张图片)，将视频帧传输到客户端(浏览器)，这里有很多成熟的传输技术，包括：HLS、RTSP、RTMP等。这些技术有一定的复杂性，各自有其适用场景，如果业务场景对实时性、性能没有太高要求，那显得有点牛刀杀鸡了。我们选择http的multipart类型，这是一个简单的方案，我们主要是理解架构：
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![0009_USB_Camera_to_IP_WebCamera.png](images/0009_USB_Camera_to_IP_WebCamera.png)
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## IP Camera实践
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* cat /etc/pip.conf
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```
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[global]
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timeout = 600
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index-url = https://pypi.tuna.tsinghua.edu.cn/simple
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extra-index-url = https://pypi.tuna.tsinghua.edu.cn/simple
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```
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* sudo pip3 install flask
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* Flask是一个使用Python编写的轻量级Web应用程序框架。
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* sudo apt-get install cmake
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* sudo pip3 install opencv-python
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* 安装时间挺长，挺住，编译源代码的时候好像只用了一个核，所以很慢，我这边安装了差不多一个半小时；
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* 可以通过top命令查看情况
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* https://github.com/LowLevelOfLogic/RaspberryPi/tree/IP_Camera
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* [OpenCV人脸识别模型haarcascade_frontalface_alt.xml，模型来自这里](https://github.com/TimeIvyace/OpenCV-PCA-KNN-SVM_face_recognition)

‎docs/0010_Tmux_Vim_Ctags_Cscope代码分析.md‎

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# Tmux Vim Ctags Cscope代码分析
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在Linux命令行如何阅读代码？
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## 参考文档
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* http://cscope.sourceforge.net/cscope_maps.vim
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* [How to let cscope use absolute path in cscope.out file?](https://stackoverrun.com/cn/q/450057)
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## Tmux分屏
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* cat ~/.tmux.conf
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```
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set -g default-terminal "screen-256color"
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set -g history-limit 10000
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# Easy config reload
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bind r source-file ~/.tmux.conf \; display-message "tmux.conf reloaded"
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bind C-a source-file ~/.tmux/layout/mylayout \; display-message "tmux.conf reloaded"
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# Use Alt-arrow keys to switch panes
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unbind-key j
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bind-key j select-pane -D
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unbind-key k
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bind-key k select-pane -U
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unbind-key h
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bind-key h select-pane -L
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unbind-key l
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bind-key l select-pane -R
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unbind '"'
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bind - splitw -v -c '#{pane_current_path}' # 垂直方向新增面板，默认进入当前目录
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unbind %
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bind | splitw -h -c '#{pane_current_path}' # 水平方向新增面板，默认进入当前目录
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```
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## Vim Ctags
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* sudo apt-get install vim universal-ctags
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* make ARCH=arm tags
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* 要等得挺久才行
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* cat ~/.vimrc
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```
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set mouse-=a
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syntax on
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set hlsearch
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hi Search ctermbg=white
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hi Search ctermfg=black
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set tabstop=4
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set shiftwidth=4
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"set expandtab
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set tags+=/home/pi/zengjf/linux-rpi-5.4.y/tags
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```
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## Vim Cscope
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* sudo apt-get install cscope
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* make ARCH=arm cscope
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* ls cscope*
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* cat ~/.vimrc
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```
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set mouse-=a
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syntax on
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set hlsearch
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hi Search ctermbg=white
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hi Search ctermfg=black
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set tags+=/home/pi/zengjf/linux-rpi-5.4.y/tags
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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" cscope setting
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if has("cscope")
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set csprg=/usr/bin/cscope
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set csto=1
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set cst
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set nocsverb
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" add any database in current directory
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" if filereadable("cscope.out")
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" cs add cscope.out
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" endif
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cs add /home/pi/zengjf/helloworld/cscope.out /home/pi/zengjf/helloworld
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cs add /home/pi/zengjf/linux-rpi-5.4.y/cscope.out /home/pi/zengjf/linux-rpi-5.4.y
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set csverb
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endif
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nmap <C-\>s :cs find s <C-R>=expand("<cword>")<CR><CR>
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nmap <C-\>g :cs find g <C-R>=expand("<cword>")<CR><CR>
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nmap <C-\>c :cs find c <C-R>=expand("<cword>")<CR><CR>
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nmap <C-\>t :cs find t <C-R>=expand("<cword>")<CR><CR>
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nmap <C-\>e :cs find e <C-R>=expand("<cword>")<CR><CR>
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nmap <C-\>f :cs find f <C-R>=expand("<cfile>")<CR><CR>
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nmap <C-\>i :cs find i ^<C-R>=expand("<cfile>")<CR>$<CR>
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nmap <C-\>d :cs find d <C-R>=expand("<cword>")<CR><CR>
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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```
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* s: 查找C语言符号，即查找函数名、宏、枚举值等出现的地方
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* g: 查找函数、宏、枚举等定义的位置，类似ctags所提供的功能
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* d: 查找本函数调用的函数
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* c: 查找调用本函数的函数
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* t: 查找指定的字符串
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* e: 查找egrep模式，相当于egrep功能，但查找速度快多了
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* f: 查找并打开文件，类似vim的find功能
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* i: 查找包含本文件的文

‎docs/0011_SoC设备树DTS分析.md‎

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# SoC设备树DTS分析
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怎么分析芯片设备树
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## 配置bash环境变量
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* tail ~/.bashrc
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```
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# ...省略
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LINUX_SRC=/home/pi/zengjf/linux-rpi-5.4.y
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alias kernel="cd ${LINUX_SRC}"
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alias dts="cd ${LINUX_SRC}/arch/arm/boot/dts"
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```
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* 便于代码目录跳转
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## SoC Datasheet
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* [Raspberry Pi 4 B Datasheets](https://www.raspberrypi.org/documentation/hardware/raspberrypi/datasheets.md)
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* [rpi_DATA_2711_1p0.pdf](refers/datasheet/rpi_DATA_2711_1p0.pdf)
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# GPIO UART I2C DTS分析
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* arch/arm/boot/dts/bcm2711-rpi-4-b.dts
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```
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* arch/arm/boot/dts # dts目录
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* bcm2711-rpi-4-b.dts # 一般是产品的名字称，包含整个产品控制器的描述
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* #include "bcm2711.dtsi" # 一般是芯片的名称，包含基本芯片的控制器的基本描述
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* #include "bcm283x.dtsi" # 芯片是在原来芯片基础上设计的，继承原先的基础配置
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* gpio # pin脚复用配置
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* uart0 ~ 1
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* i2c0if
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* i2c1
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* uart2 ~ 5
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* i2c3 ~ 6
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```
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* Chapter 3. BSC
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* i2c
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* Chapter 5. General Purpose I/O (GPIO)
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* gpio
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* Chapter 11. UART
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* uart
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## DTS如何关联Driver
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* arch/arm/boot/dts/bcm2711-rpi-4-b.dts
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```
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* arch/arm/boot/dts # dts目录
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* bcm2711-rpi-4-b.dts # dts文件
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* i2c3: i2c@7e205600 # i2c3控制器
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* compatible = "brcm,bcm2711-i2c", "brcm,bcm2835-i2c"; # 控制器与驱动match字段
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* cd drivers/i2c # 查找i2c驱动目录
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* ack brcm,bcm2711-i2c # 查找match字段
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* busses/i2c-bcm2835.c # 驱动文件
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* { .compatible = "brcm,bcm2711-i2c" }, # 驱动match字段
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```
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* of: Open Firmware
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## Device Driver match
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* 打印probe内核调用栈：
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```diff
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diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
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index 9f4f496..792f20e 100644
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--- a/drivers/i2c/busses/i2c-bcm2835.c
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+++ b/drivers/i2c/busses/i2c-bcm2835.c
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@@ -517,6 +517,8 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
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struct clk *mclk;
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u32 bus_clk_rate;
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+ dump_stack();
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+
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i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
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if (!i2c_dev)
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return -ENOMEM;
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```
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* KERNEL=kernel7l
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* make -j4 zImage modules dtbs
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```
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CALL scripts/atomic/check-atomics.sh
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CALL scripts/checksyscalls.sh
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CHK include/generated/compile.h
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CC [M] drivers/i2c/busses/i2c-bcm2835.o
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Kernel: arch/arm/boot/Image is ready
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Building modules, stage 2.
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MODPOST 1626 modules
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Kernel: arch/arm/boot/zImage is ready
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CC [M] drivers/i2c/busses/i2c-bcm2835.mod.o
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LD [M] drivers/i2c/busses/i2c-bcm2835.ko
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```
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* uname -a
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```
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Linux raspberrypi 5.4.83-v7l #1 SMP Wed Feb 10 09:33:55 GMT 2021 armv7l GNU/Linux
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```
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* sudo cp drivers/i2c/busses/i2c-bcm2835.ko /lib/modules/5.4.83-v7l/kernel/drivers/i2c/busses/i2c-bcm2835.ko
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* sudo raspi-config
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* i2c
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* vim /boot/config.txt
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* dtparam=i2c_arm=on
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* dmesg
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```
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...省略
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[ 287.688821] OF: overlay: WARNING: memory leak will occur if overlay removed, property: /soc/i2c@7e804000/status
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[ 287.730053] CPU: 1 PID: 787 Comm: systemd-udevd Tainted: G C 5.4.83-v7l #1
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[ 287.730060] Hardware name: BCM2711
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[ 287.730063] Backtrace:
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[ 287.730080] [<c020dfb0>] (dump_backtrace) from [<c020e330>] (show_stack+0x20/0x24)
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[ 287.730086] r7:ffffffff r6:00000000 r5:a0000013 r4:c129fab0
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[ 287.730095] [<c020e310>] (show_stack) from [<c0a76c34>] (dump_stack+0xd8/0x11c)
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[ 287.730113] [<c0a76b5c>] (dump_stack) from [<bf36a9b4>] (bcm2835_i2c_probe+0x34/0x388 [i2c_bcm2835])
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[ 287.730118] r10:00000000 r9:00000023 r8:c1204fc8 r7:d6a05e00 r6:d6a05e10 r5:00000000
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[ 287.730122] r4:d6a05e10 r3:cbd15570
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[ 287.730133] [<bf36a980>] (bcm2835_i2c_probe [i2c_bcm2835]) from [<c07969ec>] (platform_drv_probe+0x58/0xa8)
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[ 287.730138] r9:00000023 r8:bf36c014 r7:00000000 r6:bf36c014 r5:00000000 r4:d6a05e10
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[ 287.730145] [<c0796994>] (platform_drv_probe) from [<c07949c0>] (really_probe+0x1f0/0x354)
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[ 287.730150] r7:00000000 r6:c13616b4 r5:d6a05e10 r4:c13616b0
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[ 287.730156] [<c07947d0>] (really_probe) from [<c0794d1c>] (driver_probe_device+0x70/0x184)
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[ 287.730161] r10:c1204fc8 r9:d5a8ff30 r8:bf36c080 r7:c0795028 r6:bf36c014 r5:bf36c014
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[ 287.730164] r4:d6a05e10 r3:00000000
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[ 287.730171] [<c0794cac>] (driver_probe_device) from [<c0795020>] (device_driver_attach+0x68/0x70)
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[ 287.730176] r9:d5a8ff30 r8:bf36c080 r7:c0795028 r6:bf36c014 r5:00000000 r4:d6a05e10
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[ 287.730182] [<c0794fb8>] (device_driver_attach) from [<c0795090>] (__driver_attach+0x68/0xdc)
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[ 287.730187] r7:c0795028 r6:d6a05e10 r5:bf36c014 r4:00000000
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[ 287.730193] [<c0795028>] (__driver_attach) from [<c07929c8>] (bus_for_each_dev+0x84/0xc4)
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[ 287.730197] r7:c0795028 r6:bf36c014 r5:c1204fc8 r4:d5943db4
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[ 287.730203] [<c0792944>] (bus_for_each_dev) from [<c0794218>] (driver_attach+0x2c/0x30)
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[ 287.730207] r7:00000000 r6:d736ae80 r5:c12713b8 r4:bf36c014
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[ 287.730214] [<c07941ec>] (driver_attach) from [<c0793c30>] (bus_add_driver+0x1c8/0x1e8)
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[ 287.730220] [<c0793a68>] (bus_add_driver) from [<c079574c>] (driver_register+0x84/0x118)
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[ 287.730224] r7:00000000 r6:d60a2d00 r5:bf077000 r4:bf36c014
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[ 287.730231] [<c07956c8>] (driver_register) from [<c0796940>] (__platform_driver_register+0x50/0x58)
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[ 287.730234] r5:bf077000 r4:c1204fc8
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[ 287.730244] [<c07968f0>] (__platform_driver_register) from [<bf077028>] (bcm2835_i2c_driver_init+0x28/0x1000 [i2c_bcm2835])
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[ 287.730252] [<bf077000>] (bcm2835_i2c_driver_init [i2c_bcm2835]) from [<c02030c4>] (do_one_initcall+0x50/0x25c)
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[ 287.730260] [<c0203074>] (do_one_initcall) from [<c02c28fc>] (do_init_module+0x70/0x264)
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[ 287.730265] r8:bf36c080 r7:d60a2d40 r6:d60a2d00 r5:d60a2740 r4:bf36c080
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[ 287.730271] [<c02c288c>] (do_init_module) from [<c02c4f58>] (load_module+0x236c/0x2670)
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[ 287.730274] r6:d60a2d00 r5:00000002 r4:00000002
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[ 287.730280] [<c02c2bec>] (load_module) from [<c02c54c0>] (sys_finit_module+0xd4/0xec)
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[ 287.730285] r10:0000017b r9:d5a8e000 r8:c02011c4 r7:00000006 r6:b6e2f8e0 r5:00000000
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[ 287.730288] r4:c1204fc8
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[ 287.730294] [<c02c53ec>] (sys_finit_module) from [<c02011a4>] (__sys_trace_return+0x0/0x1c)
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[ 287.730298] Exception stack(0xd5a8ffa8 to 0xd5a8fff0)
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[ 287.730303] ffa0: fdfcc000 00e13b90 00000006 b6e2f8e0 00000000 b6e303f4
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[ 287.730308] ffc0: fdfcc000 00e13b90 00000000 0000017b 00e1ee40 0049b1dc 00e49ca0 00000000
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[ 287.730312] ffe0: bebbd228 bebbd218 b6e269d8 b6f16af0
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[ 287.730316] r7:0000017b r6:00000000 r5:00e13b90 r4:fdfcc000
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```

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