[linux kernel] Kernel graphical cropping configuration

System version: Ubuntu18.04-64

Compiler version: gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)

uboot version: 2018.07-linux4sam_6.0

Board model: at91sama5d3x-xplained

MCU model: sama5d36

The kernel cross-toolchain relies on the Makefile file for cascade compilation and the Kconfig file for configuration. For example, the current ESP32 also uses this graphical configuration. Good things will be widely accepted.

1. Call up the configuration interface

View the Makefile file and view version information 4.19

make menuconfig

General setup ---> //General configuration <======

[*] Enable loadable module support ---> // Enable insmod

-*- Enable the block layer ---> // Disk IO scheduling, usually the default is ok

System Type ---> //Select a specific arm core/cpu type and its properties. You should confirm this part after make menuconfig

Bus support ---> // Some bus support, usually the default is ok

Kernel Features ---> //Kernel features, such as memory distribution between application and kernel space

Boot options ---> //Boot options, features that can be modified during kernel boot process

CPU Power Management ---> // CPU power management, usually you need to make a choice in battery-powered devices

Power management options ---> // Power management of peripheral devices suspend() resum()

Networking support ---> // Network support, basically all about protocols, such as TCP/IP, domain sockets, multicast, ppp protocol

Device Drivers ---> // Device driver, including two parts: Controller === device driver, frequently visited options

File systems ---> // File system support, such as ntfs, ext4, nfs, cramfs, jiffs, minix................... yaffs, ubifs

Use * to select the compilation item

[*] 

< > You can use spaces to select

() ==> Fill in a value and press Enter, for example (arm-none-linux-gnueabi-) Cross-compiler tool prefix  

General setup --->

    [*] Configure standard kernel features (for small systems) ---> 

        [*] Sysctl syscall support (NEW)

        [*] Load all symbols for debugging/ksymoops (NEW)

        [*] Include all symbols in kallsyms

    //kernel panic, will prompt the code execution stack

System Type --->

    ARM system type (Samsung S5PC100) ---> 

    [*] SMDKC100

Kernel Features --->

    [*] Use the ARM EABI to compile the kernel //If eabi appears in the cross toolchain, be sure to select it

    [*] Allow old ABI binaries to run with this kernel (EXPERIMENTAL) 

Relationship between cmdline and bootags: Same

[ * ] Networking support --->

    Networking options ---> 

        <*> Unix domain sockets 

        [*] TCP/IP networking <===========If you have a network card, you must select one

        [*] IP: multicasting 

File systems ---> 

    <*> Ext3 journalling file system support

    <*> The Extended 4 (ext4) filesystem  

    Pseudo filesystems ---> // Virtual file system: manage files in memory. After power failure, the files will not exist. They will be temporarily created when the computer is turned on.

                // The files in dev/, proc/, and sys/ directories are all temporary

        [*] /proc file system support (NEW) 

        [*] sysfs file system support (NEW) 

        [*] Virtual memory file system support (former shm fs) 

        [*] Tmpfs POSIX Access Control Lists 

    [*] Miscellaneous filesystems ---> //Miscellaneous file systems, support for the management of files stored in nand

        <*> Compressed ROM file system support (cramfs)

        <*> SquashFS 4.0 - Squashed file system support

    [*] Network File Systems (NEW) ---> // Network file system: nfs

        <*> NFS client support 

        [*] NFS client support for NFS version 3

        [*] NFS client support for the NFSv3 ACL protocol extension

    <*> Native language support ---> //Character encoding method supported by the kernel

         <*> Codepage 437 (United States, Canada)

         <*> Simplified Chinese charset (CP936, GB2312)

         <*> ASCII (United States)  

         <*> NLS ISO 8859-1 (Latin 1; Western European Languages) 

         <*> NLS UTF-8

Device Drivers ---> 

    <*> Connector - unified userspace <-> kernelspace linker ---> 

    <*> Memory Technology Device (MTD) support ---> // There are nand, onenand and other devices, you need to select mtd

        [*] MTD partitioning support 

         [*] Command line partition table parsing //uboot can pass the partition table

         <*> NAND Device Support ---> //nand device support, specific nand controller options for a certain platform

    [*] Network device support ---> //A network card is required

    [*] Ethernet (10 or 100Mbit) (NEW) ---> 

        <*> DM9000 support

    [*] USB support --->

        <*> Support for Host-side USB  

        [*] USB device filesystem (DEPRECATED) 

        [*] USB device class-devices (DEPRECATED) (NEW) 

        <*> USB Modem (CDC ACM) support // 3G configuration

        <*> USB Serial Converter support ---> USB to serial port

[*] Networking support —>

Network card driver selection

Device Drivers --->

     [*] Network device support ---> 

        [*] Ethernet driver support --->

        -*- MDIO bus device drivers ---- //MDIO controller reads PHY registers

        -*- PHY Device support and infrastructure --->

            <*> Micrel PHYs // Micrel's ksz9031 and ksz8081

I2C Bus

    I2C support ---> 

    <*> I2C device interface //i2c driver interface

    -*- I2C bus multiplexing support  

          I2C Hardware Bus support ---> //Hardware bus

        <*> GPIO-based bitbanging I2C //Corresponding GPIO pin multiplexing

SPI Bus

 [*] SPI support ---> 

    <*> GPIO-based bitbanging SPI Master

    User mode SPI device driver support //The driver is loaded as a module and communicates with the external MCU via SPI

GPIO Bus

[*] GPIO Support --->

    [*] /sys/class/gpio/... (sysfs interface) //Support sysfs interface to facilitate debugging of character drivers

USB support, mount mouse, keyboard, and USB device

[*] USB support ---> 

    <*> Support for Host-side USB 

    [*] USB announces new devices

    <*> USB Serial Converter support ---> //USB to serial port

<*> MMC/SD/SDIO card support ---> //EMMC

    <*> MMC block device driver //Driver

    (8) Number of minors per block device //Data bus bit number

    [*] MMC host drivers debugging //Print debugging information

    <*> Secure Digital Host Controller Interface support 

    <*> SDHCI platform and OF driver helper

    <*> SDHCI OF support for the Atmel SDMMC controller

    <*> SDHCI support for the Cadence SD/SDIO/eMMC controller

[*] LED Support --->

     [*] LED Trigger support --->

        <*> LED Heartbeat Trigger //When the kernel is running normally, the heartbeat LED indicator light is on. The hardware needs to design an indicator light

Control of kernel compilation:

all:vmlinux

# Build vmlinux

# ---------------------------------------------------------------------------

# vmlinux is built from the objects selected by $(vmlinux-init) and

# $(vmlinux-main). Most are built-in.o files from top-level directories

# in the kernel tree, others are specified in arch/$(ARCH)/Makefile.

# Ordering when linking is important, and $(vmlinux-init) must be first.

#

# vmlinux

# ^

# |

# +-< $(vmlinux-init)

# | +--< init/version.o + more

# |

# +--< $(vmlinux-main)

# | +--< driver/built-in.o mm/built-in.o + more

# |

# +-< kallsyms.o (see description in CONFIG_KALLSYMS section)

=============>

init-y := init/

drivers-y := drivers/ sound/ firmware/

net-y := net/

libs-y := lib/

core-y := usr/

==================================

vmlinux-init := $(head-y) $(init-y)

vmlinux-main := $(core-y) $(libs-y) $(drivers-y) $(net-y)

vmlinux-all := $(vmlinux-init) $(vmlinux-main)

vmlinux-lds := arch/$(SRCARCH)/kernel/vmlinux.lds //Link script arch/arm/kernel/vmlinux.lds

head-y cannot be found in the top-level Makefile: actually in arch/arm/Makefile

include $(srctree)/arch/$(SRCARCH)/Makefile

ifeq ($(CONFIG_MMU),) // CONFIG_MMU must not be empty, CONFIG_MMU=y

MMUEXT := -nommu

endif

head-y := arch/arm/kernel/head.o arch/arm/kernel/init_task.o

arch/arm/kernel/head.S //Entry file

arch/arm/kernel/vmlinux.lds //Link script

OUTPUT_ARCH(arm)

ENTRY(stext) //Entry function

SECTIONS

{

 . = 0xC0000000 + 0x00008000; // Space above 3G

 .init : { /* Init code and data Contains code and data. free 144K mem */

  _stext = .; // Starting segment

  _sinittext = .;

   *(.head.text) // There is a text section

   *(.init.text) *(.cpuinit.text) *(.meminit.text)

  _einittext = .;

  __proc_info_begin = .; //Starting position

   *(.proc.info.init) // Special segment, very similar to the .u_boot_cmd segment

  __proc_info_end = .; //End position

  __arch_info_begin = .;

   *(.arch.info.init)

  __arch_info_end = .;

  __tagtable_begin = .;

   *(.taglist.init)

  __tagtable_end = .;

========================================================

Relationship between Kconfig---> Makefile

make menuconfig --> Kcongfig in each directory ==> save .config

CONFIG_CPU_S5PC100=y 

 ==> Kbuild processing: 1, to Makefile

         obj-$(CONFIG_CPU_S5PC100) += cpu.o init.o clock.o gpiolib.o irq-gpio.o

        2. Generate a header file for use in C language code

        ./include/generated/autoconf.h:98:#define CONFIG_CPU_S5PC100 1

        #define CONFIG_CPU_S5PC100 1

        If CONFIG_INET6_XFRM_MODE_TUNNEL value is y

            #define CONFIG_INET6_XFRM_MODE_TUNNEL 1

        If CONFIG_INET6_XFRM_MODE_TUNNEL value is m

            #define CONFIG_INET6_XFRM_MODE_TUNNEL_MODULE 1

================================================

If you compile the code mytest.c in the kernel

1. Write Kcongfig

    config MY_TEST

        tristate "this is a config test"

        help

          this is a help info to choose my_test

    Writing a Makefile

    obj-$(CONFIG_MY_TEST) += mytest.o

2. Modify the Makfile directly

    obj-y += mytest.o

    File systems --->

    <*> The Extended 4 (ext4) filesystem