Embedded system migration [8] - device tree and root file system migration

Linux Device driver porting

Device tree

    Device tree Is a description of hardware Information Data structure of ,Linux When the kernel is running, the hardware information can be passed directly to through the device tree Linux kernel , And no longer need to be in Linux The kernel contains a lot of redundant coding

Device tree syntax overview

Device tree file

    dts  Device tree source file

    dtsi Similar to header file , Contains some public information , Can be referenced by other device tree files

    dtb  Compiled device tree file

Device tree syntax

    The syntax of the device tree is tree structure , It consists of a series of nodes and attributes , The root node contains child nodes

    Child nodes can also be included under child nodes , The node contains the attributes of the corresponding device

Linux Kernel driver migration

  1. stay make menuconfig Select the driver to be installed in the interface

  2. Add... To the device tree / Modify the corresponding equipment information

  3. Recompile the kernel / Device tree

Experiment 8   Network card driver transplantation

【 The experiment purpose 】

master Linux Basic methods of kernel configuration , Complete the network card drive 、NFS And other related functions

【 Experimental environment 】

1、 ubuntu 14.04 Distribution version

2、 FS4412 The experiment platform

3、 Cross compiler tool ：arm-none-linux-gnueabi-

【 matters needing attention 】

1、 In the experimental steps “$” The first command means ubuntu Execution in environment , With “#” The first command means to execute under the development board

【 The experimental steps 】

1、 Execute the following commands under the top directory of the kernel source code , Modify kernel configuration

 $ make   menuconfig                                                                                                    

Optional for the kernel DM9000 Network card driver , And then choose “Save” preservation

Device Drivers    ---> [*] Network device support    ---> [*]     Ethernet driver support    ---> <*>     DM9000 support

 

Because the kernel uses NFS Mount the root file system , and NFS Is based on TCP Protocol implemented , So here we need Optional TCP Related network protocols （ Some functions have been selected by default ）, And then choose “Save” preservation

[*] Networking support    ---> Networking options    ---> <*> Packet socket <*> Unix domain sockets [*] TCP/IP networking [*]     IP: kernel level autoconfiguration

 

Because the kernel uses NFS Mount the root file system , So you need to choose the kernel NFS Client and related functions

[*]     Root file system on NFS

NFS client support for the NFSv3 ACL protocol extension

[*]

NFS client support for NFS version 3 (NEW)

<*>

File systems    ---> [*] Network File Systems    ---> <*>     NFS client support

 

After setting, use the direction key to select ‘Save’ Save it , And then choose ‘Exit’ Exit the configuration interface

2、 Add the hardware information of the network card to the device tree

 $ vi   arch/arm/boot/dts/exynos4412-fs4412.dts                                                                

At the end of the file , Before the last curly bracket Add the following （ That is, it should be written in the root node ）

[email protected] { compatible = "simple-bus"; #address-cells = <1>; #size-cells = <1>; reg = <0x5000000 0x1000000>; ranges; [email protected] { compatible = "davicom,dm9000"; reg = <0x5000000 0x2 0x5000004 0x2>; interrupt-parent = <&gpx0>; interrupts = <6 4>; davicom,no-eeprom; mac-address = [00 0a 2d a6 55 a2]; }; };

 

3、 Modify clock related configuration （ Ignore useless clocks ）

$ vi    drivers/clk/clk.c                                                                                                    

take

static bool clk_ignore_unused;                                                                                         

Change to the following , Then save to exit

static bool clk_ignore_unused=true;                                                                                                                                                                                 4、 modify EMMC Related configuration

$ vi    drivers/mmc/core/mmc.c                                                                                        

take

if (card->ext_csd.rev > 7) { pr_err("%s: unrecognised EXT_CSD revision %d\n", mmc_hostname(card->host), card->ext_csd.rev); err = -EINVAL; goto out; }

 

Change to the following , Then save to exit

#if 0 if (card->ext_csd.rev > 7) { #else if (card->ext_csd.rev > 8) { #endif pr_err("%s: unrecognised EXT_CSD revision %d\n", mmc_hostname(card->host), card->ext_csd.rev); err = -EINVAL; goto out; }

 

5、 Compile kernel and device tree

$ make    uImage $ make    dtbs

6、 Test the kernel and device tree

Copy the compiled kernel and device tree to tftp Working directory of

$ sudo	cp    arch/arm/boot/uImage    /tftpboot
$ sudo	cp    arch/arm/boot/dts/exynos4412-fs4412.dtb	/tftpboot/
$ sudo	chmod    777    /tftpboot/*

heavy Qi tftp and nfs The server

$ sudo    service    tftpd-hpa    restart $ sudo    service    nfs-kernel-server    restart

Restart the development board to check the phenomenon , As shown in the figure , here Linux The kernel has passed NFS Mount the root file system and execute it under the terminal ‘ls’ Command, we can see the contents of the root file system

The root file system

         The root file system is the first file system mounted after the kernel starts. The boot program will load some basic initialization scripts and services into memory to run after the root file system is mounted .

Root file system content

nbin  shell command (elf Format )( adopt busybox Compile the generated )

n dev  Device file ( kernel start-up After that, the device information will be written to this directory )

netc  Kernel configuration file

n lib  Shared library (elf Format )( Get... From the cross compilation tool chain )

n linuxrc  The first application that the kernel runs ( adopt busybox Compile the generated )

n mnt  Mount Directory ( It's not necessary )

n proc  Process related files ( kernel start-up After the will process Information is written to this directory )

nroot  The super user home Catalog ( It's not necessary )

n sbin     System management shell command (elf Format )( adopt busybox Compile the generated )

n sys  drive Related documents ( kernel start-up After the will drive Information is written to this directory )

nusr  shell command (elf Format )( adopt busybox Compile the generated )

Root file system migration

BusyBox

        BusyBox Integrate many common tools into a small executable , Provide most commonly used commands for ordinary users ,BusyBox The implemented commands are simplified , Many extensions do not support （ Some extensions with bars after commands are not supported ）.BusyBox go by the name of Linux The Swiss Army knife in the tool .

BusyBox Acquisition

        https://busybox.net/downloads/

Experiment 9   Root file system migration

【 The experiment purpose 】

Familiar with the directory structure of the root file system , Build your own root file system

【 Experimental environment 】

1、 ubuntu 14.04 Distribution version

2、 FS4412 The experiment platform

3、 Cross compiler tool ：arm-none-linux-gnueabi-

【 matters needing attention 】

1、 In the experimental steps “$” The first command means ubuntu Execution in environment

【 The experimental steps 】

One 、 Build your own root file system

1、 stay busybox Download from the official website busybox Source code （ Here we download busybox-1.22.1.tar.bz2）

Index of /downloads

2、 Copy busybox Source package to ubuntu Home directory , Unzip and enter its top-level directory

$ tar    xvf    busybox-1.22.1.tar.bz2 $ cd    busybox-1.22.1/

 

3、 Get into busybox Configuration interface （ And Linux The kernel configuration method is the same ）

$ make    menuconfig                                                                                                     

4、 Refer to the following information to configure busybox

Busybox Settings    ---> Build Options    ---> [*] Build BusyBox as a static binary (no shared libs) [ ] Build with Large File Support (for accessing files > 2 GB) (arm-none-linux-gnueabi-) Cross Compiler prefix

 

After the configuration is completed, select through the direction key ‘Exit’ sign out , And save the configuration information

5、 compile busybox

$ make                                                                                                                          

After compilation, it will be generated in the top-level directory of the source code busybox file

6、 install busybox

$ make    install                                                                                                             

After installation, it will be generated in the top-level directory of the source code _install Catalog

7、 Enter the installation directory to view the generated files

$ cd    _install/ $ ls

 

As shown in the figure below , Generate the required in the root file system under the installation directory shell Command file

8、 Copy the library files in the cross compilation tool chain to _install Under the table of contents

$ cp /home/linux/Linux_4412/toolchain/gcc-4.6.4/arm-arm1176jzfssf-linux-gnueabi/lib/ . -a   

As shown in the figure below , In the installation directory, you have the library files required in the root file system

 

9、 Delete the static library in the library file

$ sudo    su $ /home/linux/Linux_4412/toolchain/gcc-4.6.4/bin/arm-none-linux-gnueabi-strip   lib/* $ exit

$ sudo    rm   lib/*.a                                                                                                       

10、 Delete the symbol table in the shared library （ Need to be in root User down operation ）

11、 Put the data in the database “ Migrate related files ” Under the etc Catalog （ The configuration file ） Copy to current directory

12、 to etc/init.d/ Under the rcS Script add executable rights

$ chmod    +x   etc/init.d/rcS                                                                                           

13、 Create other directories

$ mkdir    dev    mnt    proc    root   sys    tmp    var                                                           

As shown in the figure below , So far, we have built our own root file system

14、 Delete the original root file system

$ sudo    rm   -rf   /opt/4412/rootfs/*                                                                               

15、 Copy your own root file system to NFS Test under the working directory of

$ sudo    cp    -rf   ./*    /opt/4412/rootfs