【ARM】Linux driver porting

#1 Driver module transplantation process

##1.1 The first module compilation method - change kconfig

Step 1: Change kconfig

The file is in: Drivers/char/kconfig;

The tristate representation can be compiled in module ;

bool means that it can only be selected to be edited [*] or not edited [ ].

Step 2: Configure the kernel

After make menuconfig, a .config file for compilation will be automatically generated.

wuchengbing@ubuntu:~/linux/kernel-2.6.13$ make menuconfig

 Device Drivers  --->  Character devices  ---> 

  [*] S3C2410 RTC Driver                                         │ │  

  QQ2440/mini2440 LEDs Driver                                │ │  

  QQ2440/mini2440 PWM beeper Driver                          │ │  

  QQ2440/mini2440 Hello Module sample                        │ │  

  QQ2440 Buttons                         

If make menuconfig does not display this option, you can first cp config_n35 .config->make-> make menuconfig, and then generate the following .config file.

wuchengbing@ubuntu:~/linux/kernel-2.6.13$ gedit .config

# CONFIG_WATCHDOG is not set

# CONFIG_NVRAM is not set

# CONFIG_RTC is not set

CONFIG_S3C2410_RTC=y

CONFIG_QQ2440_LEDS=m

CONFIG_QQ2440_PWM_BEEPER=y

CONFIG_QQ2440_HELLO_MODULE=m

… …

If you select [*], that is, yes, the driver will be automatically loaded when the system is running; if you select , you need to load the driver manually to use it.

Step 3: Compile the kernel to get the driver module

make, and then generate the corresponding driver module .ko file.

wuchengbing@ubuntu:~/linux/kernel-2.6.13$make

… …

  LD      vmlinux

  SYSMAP  System.map

  SYSMAP  .tmp_System.map

  OBJCOPY arch/arm/boot/Image

  Kernel: arch/arm/boot/Image is ready

  AS      arch/arm/boot/compressed/head.o

  GZIP    arch/arm/boot/compressed/piggy.gz

  AS      arch/arm/boot/compressed/piggy.o

  CC      arch/arm/boot/compressed/misc.o

  LD      arch/arm/boot/compressed/vmlinux

  OBJCOPY arch/arm/boot/zImage

  Kernel: arch/arm/boot/zImage is ready

  Building modules, stage 2.

  MODPOST

  CC      drivers/char/mini2440_backlight.mod.o

  LD [M]  drivers/char/mini2440_backlight.ko

  CC      drivers/char/qq2440_buttons.mod.o

  LD [M]  drivers/char/qq2440_buttons.ko

  CC      drivers/char/qq2440_hello_module.mod.o

  LD [M]  drivers/char/qq2440_hello_module.ko

  CC      drivers/char/qq2440_leds.mod.o

  LD [M]  drivers/char/qq2440_leds.ko

  CC      drivers/char/qq2440_pwm.mod.o

  LD [M]  drivers/char/qq2440_pwm.ko

wuchengbing@ubuntu:~/linux/kernel-2.6.13$

qq2440_leds.ko

wuchengbing@ubuntu:~/linux/kernel-2.6.13$ ls driver/char/

…

-rw-rw-r-- 1 wuchengbing wuchengbing 1368 Apr 17 20:38 qq2440_hello_module.o

-rw-rw-r-- 1 wuchengbing wuchengbing 3108 Apr 17 20:38 qq2440_pwm.o

-rw-rw-r-- 1 wuchengbing wuchengbing 1412 Apr 17 20:39 qq2440_hello_module.mod.o

-rw-rw-r-- 1 wuchengbing wuchengbing 2247 Apr 17 20:39 qq2440_hello_module.ko

-rw-rw-r-- 1 wuchengbing wuchengbing 1404 Apr 17 20:39 qq2440_leds.mod.o

-rw-rw-r-- 1 wuchengbing wuchengbing 3133 Apr 17 20:39 qq2440_leds.ko

-rw-rw-r-- 1 wuchengbing wuchengbing 1404 Apr 17 20:39 qq2440_pwm.mod.o

-rw-rw-r-- 1 wuchengbing wuchengbing 3957 Apr 17 20:39 qq2440_pwm.ko

./mkimage.sh

wuchengbing@ubuntu:~/linux/kernel-2.6.13$ cd arch/arm/boot/

wuchengbing@ubuntu:~/linux/kernel-2.6.13/arch/arm/boot$ ./mkimage.sh 

Image Name:   linux-2.6.13

Created:      Mon Apr 17 20:33:08 2017

Image Type:   ARM Linux Kernel Image (uncompressed)

Data Size:    1537008 Bytes = 1500.98 kB = 1.47 MB

Load Address: 0x30008000

Entry Point:  0x30008040

wuchengbing@ubuntu:~/linux/kernel-2.6.13/arch/arm/boot$

Step 4: Copy to the file system, mount the board, and insert the module

Run the compiled ./a.out of the example program, and the LED on the board will light up.

License issues require adding MODU_LICENSE("GPL") to the driver code;

... ...

module_init(qq2440_leds_init);

module_exit(qq2440_leds_exit);

MODULE_LICENSE("GPL");

Sample Program

Application, calling the board LED through the driver.

#include

#include

#include

#include

int main(void)

{

   int fd;

   int i = 0;

   fd = open("/dev/leds",O_RDONLY);

   if(fd==-1)

   {

      perror("open failed");

      exit(1);

   }

   while(1)

   {

       ioctl(fd,0,0);

       ioctl(fd,0,1);

       ioctl(fd,0,2);

       ioctl(fd,0,3);

       sleep(1);

       ioctl(fd,1,0);

       ioctl(fd,1,1);

       ioctl(fd,1,2);

       ioctl(fd,1,3);

       sleep(1);

   }

   return 0;

}

##1.2 The second module compilation method - Makefile

Step 1: Write Makefile

Step 2: Copy the kernel driver directly

Step 3: Compile

Step 4: Installation

Step 5: Insert the module and observe the phenomenon

#2Linux driver principle

##2.0 Where to start

The LED program that comes with the development board (qq2440_leds_init) [called by module_init----just know this]

##2.1 What is registration

##2.2What data does register_chrdev submit?

###2.2.1 Why is the device number 231?

How to know setting 231

http://blog.csdn.net/zjjyliuweijie/article/details/7001383

It is set to 231 because no one uses 231.

###2.2.2 Give any device name

###2.2.3 How to set up the file operation structure

Analysis of each item in file_operations

http://blog.csdn.net/sunsea1026/article/details/6586143

####What is THIS_MODULE?

THIS_MODULE is copied to owner in the code. As the name suggests, owner means the owner. When THIS_MODULE is copied to owner, it means that the structure belongs to the current module. Then who is the current module? The current module is:

####Open,close,read这些都好理解

##2.3What does register_chrdev return?

###2.3.1 Simple and efficient goto

Whether to use goto has always been a famous controversial topic. The use of goto in the Linux kernel source code is very extensive, but it is generally limited to error handling! This use of goto for error handling is really simple and efficient. Just make sure to remember to log out and release resources when handling errors! (The opposite order of normal registration and resource application)

###2.3.2 Remember what the ternary operator is?

###2.3.3 What does a return of 0 mean?

What does it mean when major returns 0?

When Major is true, it can only be > 0, because the type of major is unsigned. Therefore, when major is greater than 0, the function returns 0, indicating that the function is executed successfully!

###2.3.4 Under what circumstances will cd->major be returned?

There is only one case where Major is false, which is equal to 0. So what does major=0 mean?

When calling the register_chrdev function,

If major=0 is passed in, it means that you do not define the device number and it will be automatically assigned by the system!

If the major passed in is > 0, it means passing in a self-defined device number without the system automatically assigning it!

How do we know?

###2.3.5 How to assign secondary device numbers?

###2.3.6 What is returned if an error occurs?

What is ENOMEM?

Can you guess now what cdev_add returns?

##2.4Where are character devices registered?

##2.5What does devfs_mk_cdev achieve?

Device FileSystem Make CharDevice

The main function is to create a device file under the file system. The name of the device file is DEVICE_NAME.

###2.5.1 How to use devfs_mk_cdev parameters?

###2.5.2 MKDEV Function

Make Device

###2.5.3 Access Mode

Chmod ,0777,umask

[Reprint] stat function and structure

http://blog.sina.com.cn/s/blog_6dd1df4e0100o50q.html

###2.5.4 Phenomenon

The following is the device file generated in the file system after the driver is successfully registered.

##2.6How to implement the file_operations structure

###2.6.1 What functions does qq2440_leds_ioctl implement?

###2.6.2 Where is s3c2410_gpio_setpin

##2.7 Pin Control

Here, s3c2410_gpio_cfgpin and s3c2410_gpio_setpin are connected to the principles of the previous article "ARM Interface Technology".

##2.8 Code call relationship

##2.9module_init function

Refer to "linux driver entry function module.docx"

#appendix

Tool download link:

https://github.com/1040003585/Mini2440/tree/master/Tools