A small summary of the modular programming of Linux drivers

This article contains the basics of Linux driver modular programming, including the creation of multi-threading, latency, and makefile

With an example to illustrate

#include <linux/init.h>#include<linux/module.h>#include<linux/kernel.h>#include<linux/sched.h>#include<linux/init.h>#include<linux/timer.h>#include<linux/kthread.h>#include<linux/delay.h>#include<linux/sched.h>#include<linux/completion.h>#include<linux/signal.h>#include<asm/processor.h>#include<asm/system.h>#include<linux/param.h>#include<linux/gpio.h>#include"gpio-sama5d3-test.h"//if there is no corresponding. h file, please note//staticdeclare_completion (my_completion);Static structTask_struct *task;intFlag =0;intMy_function (void*Arg) {//PRINTK ("in%s () \ n", __function__);allow_signal (SIGKILL);//allows threads to receive Sigkill signalsMdelay ( -); PRINTK ("should stop:%d\n", Kthread_should_stop ());  while(!signal_pending (current) &&!kthread_should_stop ())//so that the thread can be killed or it can end in Rmmod.{PRINTK ("Jiffies is%lu\n", jiffies);             Set_current_state (task_interruptible); Schedule_timeout (HZ*5);        These two sentences are for the delay of 5s, within which the processor handles other processes. PRINTK ("should stop:%d\n", Kthread_should_stop ()); } PRINTK ("Leaving my_function\n"); Flag=1; return 0;}Static int__init Sama5d3_gpio_init (void) {PRINTK ("sama5d3 Gpio init!\n") ;Task= Kthread_run (My_function,null,"my_function");//PRINTK ("<1> init wait_for_completion () \ n"); return 0;}Static void__exit Sama5d3_gpio_exit (void){    intret; PRINTK ("sama5d3 Gpio exit!\n"); if(!flag) {        if(!Is_err (Task)) {ret=kthread_stop (Task); PRINTK (Kern_info"First thread function has stopped, return%d\n", ret); }    }//PRINTK ("task_struct:0x%x", Task);Printk"goodbye\n"); return;} Module_init (Sama5d3_gpio_init); Module_exit (Sama5d3_gpio_exit); Module_author ("Huangjjy"); Module_description ("GPIO driver for sama5d3"); Module_license ("GPL");

Makefile as follows:

ifeq ($ (kernelrelease),) #KERNEL_DIR=/home/user/project2/atmel/linux-at91///If cross-compiling, this is the kernel pathKernel_dir? =/lib/modules/$ (Shell uname-r)/buildpwd:=$ (shell pwd) #CROSS_COMPILE=/home/user/project2/atmel/toolchain/gcc-linaro-arm-linux-gnueabihf-4.7-2013.04-20130415_linux/bin/arm-linux-gnueabihf-#CC=$ (cross_compile) GCC//If it is cross-compiling, this is the cross-compilation tool chain name and path
#INCLUDE = $ (PWD)/gpio-sama5d3-test.h//if the. c file has a. h file, which is the path of. h Modules: $ (make)-C $ (kernel_dir) m=$ (PWD) modules #$ (make)-i$ (INCLUDE)-C $ (Kernel_dir) m=$ (PWD) modules//if the. C file has an. h file, use this compilation syntax. Phony:modules Cleanc Lean: $ (make)-C $ (kernel_dir) m=$ (PWD) cleanElseobj-M: = gpio-sama5d3-Test.oendif

After you have finished writing the above two files, save the exit.

# make

The. ko file is generated

# insmod ****.ko-------Mount Drive

#lsmod--------to view mounted drivers

#rmmod ***.ko------Unloading Drive

#dmesg or DMESG | TAIL-20 Viewing drive printing information

#dmesg-C-----Erase printing information

A small summary of the modular programming of Linux drivers