jz2440_LED_设备树之点亮LED灯
https://blog.csdn.net/huanting_123/article/details/89608501
简介：设备驱动程序中，总线驱动模型和设备树的差别在于平台设备的构建不同，在传统平台设备驱动程序写在C文件中，使用设备树时，平台设备之前不存在，在dts文件中构造节点，节点里面含有资源，设备树详细的内容我会在以后的博客中详细介绍。
CPU : jz2440
u-boot: u-boot-1.1.6
kernel: linux-4.19-rc3
root ：fs_mini_mdev_new
1 /* platform_device结构体定义 */
2 struct platform_device {
3 const char *name;
4 int id;
5 bool id_auto;
6 struct device dev;
7 u32 num_resources;
8 struct resource *resource;
9
10 const struct platform_device_id *id_entry;
11 char *driver_override; /* Driver name to force a match */
12
13 /* MFD cell pointer */
14 struct mfd_cell *mfd_cell;
15
16 /* arch specific additions */
17 struct pdev_archdata archdata;
18 };
19
20 /* platform_device示例 */
21 struct platform_driver led_drv = {
22 .probe = led_probe,
23 .remove = led_remove,
24 .driver = {
25 .name = "myled",
26 }
27 };
28
29 /* platform_driver结构体定义 */
30 struct platform_driver {
31 int (*probe)(struct platform_device *);
32 int (*remove)(struct platform_device *);
33 void (*shutdown)(struct platform_device *);
34 int (*suspend)(struct platform_device *, pm_message_t state);
35 int (*resume)(struct platform_device *);
36 struct device_driver driver;
37 const struct platform_device_id *id_table;
38 bool prevent_deferred_probe;
39 };
40
41 /* platform_driver结构体示例 */
42 struct platform_driver led_drv = {
43 .probe = led_probe,
44 .remove = led_remove,
45 .driver = {
46 .name = "myled",
47 }
48 };
由于本文档的目的是简单介绍传统的总线驱动模型和设备树的区别，总线驱动模型的详细就不再介绍，详细介绍可以参考linux设备驱动模型之总线、设备、驱动三者的关系
下面简单分析设备树的匹配
static int platform_match(struct device *dev, struct device_driver *drv)
{
struct platform_device *pdev = to_platform_device(dev);
struct platform_driver *pdrv = to_platform_driver(drv);
/* When driver_override is set, only bind to the matching driver */
if (pdev->driver_override)
return !strcmp(pdev->driver_override, drv->name);
/* Attempt an OF style match first */
if (of_driver_match_device(dev, drv)) //用于判断从设备树得到的platform_device与platform_driver是否匹配
return 1;
/* Then try ACPI style match */
if (acpi_driver_match_device(dev, drv))
return 1;
/* Then try to match against the id table */
if (pdrv->id_table)
return platform_match_id(pdrv->id_table, pdev) != NULL;
/* fall-back to driver name match */
return (strcmp(pdev->name, drv->name) == 0);
}
static inline int of_driver_match_device(struct device *dev,
const struct device_driver *drv)
{
return of_match_device(drv->of_match_table, dev) != NULL;
}
static inline int of_driver_match_device(struct device *dev,
const struct device_driver *drv)
{
return of_match_device(drv->of_match_table, dev) != NULL;
}
根据上面的函数可以看出，从设备树得到的platform_device中的节点和platform_driver中的of_device_id是否匹配，匹配成功之后，就会调用platform_driver中的probe函数。
/dts-v1/;
/ {
model = "SMDK24440";
compatible = "samsung,smdk2440";
#address-cells = <1>;
#size-cells = <1>;
memory@30000000 {
device_type = "memory";
reg = <0x30000000 0x4000000>;
};
/*
cpus {
cpu {
compatible = "arm,arm926ej-s";
};
};
*/
chosen {
bootargs = "noinitrd root=/dev/mtdblock4 rw init=/linuxrc
console=ttySAC0,115200";
};
led {
compatible = "jz2440_led";
pin = <S3C2410_GPF(5)>;
};
};
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
static int led_pin;
static volatile unsigned int *gpio_con;
static volatile unsigned int *gpio_dat;
/* 123. 分配/设置/注册file_operations
* 4. 入口
* 5. 出口
*/
static int major;
static struct class *led_class;
static unsigned int gpio_base[] = {
0x56000000, /* GPACON */
0x56000010, /* GPBCON */
0x56000020, /* GPCCON */
0x56000030, /* GPDCON */
0x56000040, /* GPECON */
0x56000050, /* GPFCON */
0x56000060, /* GPGCON */
0x56000070, /* GPHCON */
0, /* GPICON */
0x560000D0, /* GPJCON */
};
static int led_open (struct inode *node, struct file *filp)
{
/* 把LED引脚配置为输出引脚 */
/* GPF5 - 0x56000050 */
int bank = led_pin >> 16;
int base = gpio_base[bank];
int pin = led_pin & 0xffff;
gpio_con = ioremap(base, 8);
if (gpio_con) {
printk("ioremap(0x%x) = 0x%x\n", base, gpio_con);
}
else {
return -EINVAL;
}
gpio_dat = gpio_con + 1;
*gpio_con &= ~(3<<(pin * 2));
*gpio_con |= (1<<(pin * 2));
return 0;
}
static ssize_t led_write (struct file *filp, const char __user *buf, size_t size, loff_t *off)
{
/* 根据APP传入的值来设置LED引脚 */
unsigned char val;
int pin = led_pin & 0xffff;
copy_from_user(&val, buf, 1);
if (val)
{
/* 点灯 */
*gpio_dat &= ~(1<<pin);
}
else
{
/* 灭灯 */
*gpio_dat |= (1<<pin);
}
return 22; /* 已写入1个数据 */
}
static int led_release (struct inode *node, struct file *filp)
{
printk("iounmap(0x%x)\n", gpio_con);
iounmap(gpio_con);
return 0;
}
static struct file_operations myled_oprs = {
.owner = THIS_MODULE,
.open = led_open,
.write = led_write,
.release = led_release,
};
static int led_probe(struct platform_device *pdev)
{
struct resource *res;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (res) {
led_pin = res->start;
}
else {
/* 获得pin属性 */
of_property_read_s32(pdev->dev.of_node, "pin", &led_pin);
}
if (!led_pin)
{
printk("can not get pin for led\n");
return -EINVAL;
}
major = register_chrdev(0, "myled", &myled_oprs);
led_class = class_create(THIS_MODULE, "myled");
device_create(led_class, NULL, MKDEV(major, 0), NULL, "led"); /* /dev/led */
return 0;
}
static int led_remove(struct platform_device *pdev)
{
unregister_chrdev(major, "myled");
device_destroy(led_class, MKDEV(major, 0));
class_destroy(led_class);
return 0;
}
static const struct of_device_id of_match_leds[] = {
{ .compatible = "jz2440_led", .data = NULL },
{ /* Sentinel */ }
};
struct platform_driver led_drv = {
.probe = led_probe,
.remove = led_remove,
.driver = {
.name = "myled",
.of_match_table = of_match_leds, //能支持哪些来自于dts的platform_device
}
};
static int myled_init(void)
{
platform_driver_register(&led_drv);
return 0;
}
static void myled_exit(void)
{
platform_driver_unregister(&led_drv);
}
module_init(myled_init);
module_exit(myled_exit);
MODULE_LICENSE("GPL");
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