Recently, we are working on a board of Ruixin micro platform , model ：rk3399
, Just started these days , I've been working on the environment a few days ago , Be familiar with this board , This board runs Android7.1 System of . There are not a lot of things that open to this on the Internet , I also want to make a record . then , Let's go ：
I have been familiar with the directory structure of this board , Where is the device tree file , And compiling scripts , About compiling source code ,firefly The forum also talked about , I won't say much about this one , Let's talk about what I did first ： Wrote one led drive , It's simple , The purpose, of course, is to light the lights , Let's experience how the driver of this platform is different from what I have been exposed to before , So test it first , Here are some of the ways I use them ：
* Compile into kernel , This way Power on System 1 , The module will be loaded automatically at a certain time , Enter the driver's probe, This is the only difference between the two approaches
* difference ： module_platform_driver(led_driver); module_exit(led_exit);
MODULE_LICENSE("GPL");
3. Does not compile into the kernel
Driver writing mode :1. Character device registration 2. Register as miscellaneous device
Direct code ：
#include <linux/kernel.h> #include <linux/gpio.h> #include <linux/init.h>
#include <linux/module.h> #include <linux/delay.h> #include <linux/of.h>
#include <linux/of_gpio.h> #include <linux/of_platform.h> #include
<linux/version.h> #include <linux/init.h> #include <linux/fs.h> #include
<linux/sched.h> #include <linux/pm.h> #include <linux/sysctl.h> #include
<linux/proc_fs.h> //#include <linux/platform_device.h> #include <asm/uaccess.h>
#include <asm/io.h> #define GPIO_LOW 0 #define GPIO_HIGH 1 int gpio; int major;
static struct class *cls; static int led_open(struct inode *inode, struct file
*file) { printk(KERN_EMERG "%s-%d: enter\n",__FUNCTION__,__LINE__);
return 0; } static ssize_t led_write(struct file *file, const char __user
*buf, size_t count, loff_t * ppos) { int val; int ret;
printk(KERN_EMERG "%s-%d: enter\n",__FUNCTION__,__LINE__); ret =
copy_from_user(&val, buf, count); // copy_to_user(); if (val == 1) {
gpio_set_value(gpio,GPIO_LOW); } else {
gpio_set_value(gpio,GPIO_HIGH); } return 0; } static struct
file_operations led_fops = { .owner = THIS_MODULE, .open =
led_open, .write = led_write, }; static int
led_probe(struct platform_device *pdev) { int ret ; int i; enum
of_gpio_flags flag; struct device_node *led_node = pdev->dev.of_node;
printk(KERN_EMERG "%s-%d: enter\n",__FUNCTION__,__LINE__); gpio =
of_get_named_gpio_flags(led_node,"led-gpio", 0,&flag); if
(!gpio_is_valid(gpio)){ printk(KERN_INFO "hello: invalid gpio :
%d\n",gpio); return -1; } ret = gpio_request(gpio, "led");
if (ret) { gpio_free(gpio); return -EIO; }
gpio_direction_output(gpio, GPIO_HIGH); for(i=0; i < 10; i++) {
gpio_set_value(gpio,GPIO_LOW); mdelay(500);
gpio_set_value(gpio,GPIO_HIGH); mdelay(500); } major
= register_chrdev(0, "myled", &led_fops); cls = class_create(THIS_MODULE,
"myled"); device_create(cls, NULL, MKDEV(major, 0), NULL, "led");
gpio_set_value(gpio,GPIO_LOW); printk(KERN_INFO "%s-%d:
exit\n",__FUNCTION__,__LINE__); return 0; //return Ok }
static int led_remove(struct platform_device *pdev) { printk(KERN_INFO
"Enter %s\n", __FUNCTION__); gpio_free(gpio); device_destroy(cls,
MKDEV(major, 0)); class_destroy(cls); unregister_chrdev(major,
"myled"); return 0; } static const struct of_device_id of_led_match[] = {
{ .compatible = "led_test" }, { /* Sentinel */ } }; static struct
platform_driver led_driver = { .probe = led_probe, .remove
= led_remove, .driver = { .name = "led",
.owner = THIS_MODULE, .of_match_table = of_led_match, }, };
static int __init led_init(void) { printk(KERN_INFO "Enter %s\n",
__FUNCTION__); return platform_driver_register(&led_driver); return 0;
} static void __exit led_exit(void) {
platform_driver_unregister(&led_driver); printk(KERN_INFO "Exit Hello
world\n"); } module_init(led_init); module_exit(led_exit);
MODULE_LICENSE("GPL");
Another one
#include <linux/kernel.h> #include <linux/gpio.h> #include
<linux/miscdevice.h> #include <linux/init.h> #include <linux/module.h> #include
<linux/delay.h> #include <linux/of.h> #include <linux/of_gpio.h> #include
<linux/of_platform.h> #include <linux/version.h> #include <linux/init.h>
#include <linux/fs.h> #include <linux/sched.h> #include <linux/pm.h> #include
<linux/sysctl.h> #include <linux/proc_fs.h> //#include
<linux/platform_device.h> #include <asm/uaccess.h> #include <asm/io.h> #define
GPIO_LOW 0 #define GPIO_HIGH 1 int gpio; int major; static long hello_ioctl(
struct file *files, unsigned int cmd, unsigned long arg){ //printk("cmd is
%d,arg is %d\n",cmd,arg); if(cmd > 1){ printk(KERN_EMERG "cmd is 0 or 1\n"); }
if(arg > 1){ printk(KERN_EMERG "arg is only 1\n"); } gpio_set_value(gpio,cmd);
return 0; } static int hello_release(struct inode *inode, struct file *file){
printk(KERN_EMERG "hello release\n"); return 0; } static int hello_open(struct
inode *inode, struct file *file){ printk(KERN_EMERG "hello open\n"); return 0;
} static struct file_operations hello_ops = { .owner = THIS_MODULE, .open =
hello_open, .release = hello_release, .unlocked_ioctl = hello_ioctl, }; static
struct miscdevice hello_dev = { .minor = MISC_DYNAMIC_MINOR, .name =
"hello-ctl", .fops = &hello_ops, }; static int led_probe(struct platform_device
*pdev) { int ret ; int i; enum of_gpio_flags flag; struct device_node *led_node
= pdev->dev.of_node; printk(KERN_EMERG "%s-%d: enter\n",__FUNCTION__,__LINE__);
gpio = of_get_named_gpio_flags(led_node,"led-gpio", 0,&flag); if
(!gpio_is_valid(gpio)){ printk(KERN_INFO "hello: invalid gpio : %d\n",gpio);
return -1; } ret = gpio_request(gpio, "led"); if (ret) { gpio_free(gpio);
return -EIO; } gpio_direction_output(gpio, GPIO_HIGH); for(i=0; i < 10; i++) {
gpio_set_value(gpio,GPIO_LOW); mdelay(500); gpio_set_value(gpio,GPIO_HIGH);
mdelay(500); } misc_register(&hello_dev); gpio_set_value(gpio,GPIO_LOW);
printk(KERN_INFO "%s-%d: exit\n",__FUNCTION__,__LINE__); return 0; //return Ok
} static int led_remove(struct platform_device *pdev) { printk(KERN_EMERG
"\tremove\n"); gpio_free(gpio); misc_deregister(&hello_dev); return 0; } static
const struct of_device_id of_led_match[] = { { .compatible = "led_test" }, { /*
Sentinel */ } }; static struct platform_driver led_driver = { .probe =
led_probe, .remove = led_remove, .driver = { .name = "led", .owner =
THIS_MODULE, .of_match_table = of_led_match, }, };
module_platform_driver(led_driver); module_exit(led_exit);
MODULE_LICENSE("GPL");
in addition , The driver under the platform , Something needs to be changed in the kernel , This board involves the device tree , The device tree file needs to be modified ：
My device tree file path ：/rk3399/source/g3399-v7-1-2-20180529/kernel/arch/arm64/boot/dts/rockchip
Maybe different boards will be slightly different , Device tree file ：g3399-baseboard.dtsi（ It depends on you ）, The device tree is not described , Self study
Add content ：（ At random ）
hello-led{ compatible = "led_test"; led-gpio =
<&gpio0 8 GPIO_ACTIVE_LOW>; status = "okay"; };
The next step is to increase Kconfig and Makefile Create a new directory Put it in Directory location /path/xxxxxxx/kernel/driver/
In this directory Makefile newly added ：obj-y += test/
Kconfig newly added ：
source "drivers/test/Kconfig"
above test For folder name
Next, enter test Folder Add own Makefile and Kconfig
The details are as follows ：Makefile:
obj-$(CONFIG_HELLO) += hello.o
hello It's the driver .c Name of the document CONFIG_HELLO This general naming format is CONFIG_xxx
Kconfig：
config HELLO tristate "led test" help Hello for test
Pay attention to this place there HELLO and Makefile inside CONFIG_xxx Medium xxx agreement ,tristate "led test"
The contents in double quotation marks can be modified by yourself ,help It's help information , Modify by yourself .
About procedure , There are some in the forum demo, It can be referred to , But it's up to you
About driver run results ：
g3399:/storage/0000-0000 # insmod test test.ko test_char.ko
g3399:/storage/0000-0000 # insmod test.ko
[ 355.467922] Exit Hello world [ 3372.497665] Enter led_init [ 3372.498181]
led_probe-77: enter [ 3382.500052] led_probe-104: exit g3399:/storage/0000-0000
# rmmod test [ 3385.692121] remove g3399:/storage/0000-0000 #
So far, a test program has been written , 1. Implementation , The result is very helpless （ This is the test program , Not a driver ）
g3399:/storage/0000-0000 # ./cmd_test
/system/bin/sh: ./cmd_test: can't execute: Permission denied
About its authority ：-rwxrwx--x 1 root sdcard_rw 8502 2018-11-05 00:01 cmd_test
I feel it's OK , I can't even access it , in addition ： Discover the file system usage of development board cp On command , The following problems arise ：
g3399:/storage/0000-0000 # cp -rf test.ko ../../
cp: ../..//test.ko: Read-only file system
The above reasons have been solved , The reason is that when the file system is compiled, the corresponding permissions of the file directory are not given , terms of settlement , Copy file to /data/....../...../ I can't remember the specific catalogue ,ls
-l Command to see the permissions of each directory
Note: All the orders above are in root Run under permission
Last but not least ; The device node created by the driver can be used ls /dev see
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