在设备树的dts文件里，带有compatible属性的节点就是表示一个platform_device.
在设备树里增加一个设备，则在内核里的dts文件里描述设备节点即可. 在H5方案里，则在arch/arm64/boot/dts/allwinner/sun50i-h5-nanopi-neo2.dts文件里。 如在dts文件里加入以下内容:
mynodes@77885566 { /* 则创建出来的platform_device的名为mynodes@77885566 */ compatible = "mynodes"; /* 设备节点的属性 */ autorepeat = <1>;
btn1 { /* 设备子节点 */ label = "btn1"; /* 设备子节点的属性 */ code = <0x11>; }; btn2 { label = "btn2"; code = <0x22>; }; }; 增加内容后，则重编设备树:
make dtbs ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- 1 再把编译出来的sun50i-h5-nanopi-neo2.dtb替换板上所用的dtb文件，重启系统后，可以查看到内容:
^_^ / # ls /sys/bus/platform/devices/mynodes@77885566/ driver_override of_node/ subsystem/ modalias power/ uevent
^_^ / # ls /sys/bus/platform/devices/mynodes@77885566/of_node/ autorepeat btn1/ btn2/ compatible name 1 2 3 4 5 6 在dst设备树文件描述设备后就需要与platform_driver进行匹配和驱动了. 在设备驱动里获取设备树中的设备资源需要一套接口函数来实现:
#include <linux/property.h>
//用于获取设备节点的属性成员值函数, propname用于指定要获取值的属性名 bool device_property_present(struct device *dev, const char *propname); int device_property_read_u8_array(struct device *dev, const char *propname, u8 *val, size_t nval); int device_property_read_u16_array(struct device *dev, const char *propname, u16 *val, size_t nval); int device_property_read_u32_array(struct device *dev, const char *propname, u32 *val, size_t nval); int device_property_read_u64_array(struct device *dev, const char *propname, u64 *val, size_t nval); int device_property_read_string_array(struct device *dev, const char *propname, const char **val, size_t nval); int device_property_read_string(struct device *dev, const char *propname, const char **val); int device_property_match_string(struct device *dev, const char *propname, const char *string);
//用于获取设备子节点的属性值函数. fwnode是表示子节点的对象地址 bool fwnode_property_present(struct fwnode_handle *fwnode, const char *propname); int fwnode_property_read_u8_array(struct fwnode_handle *fwnode, const char *propname, u8 *val, size_t nval); int fwnode_property_read_u16_array(struct fwnode_handle *fwnode, const char *propname, u16 *val, size_t nval); int fwnode_property_read_u32_array(struct fwnode_handle *fwnode, const char *propname, u32 *val, size_t nval); int fwnode_property_read_u64_array(struct fwnode_handle *fwnode, const char *propname, u64 *val, size_t nval); int fwnode_property_read_string_array(struct fwnode_handle *fwnode, const char *propname, const char **val, size_t nval); int fwnode_property_read_string(struct fwnode_handle *fwnode, const char *propname, const char **val); int fwnode_property_match_string(struct fwnode_handle *fwnode, const char *propname, const char *string);
struct fwnode_handle *device_get_next_child_node(struct device *dev, struct fwnode_handle *child);
---------- unsigned int device_get_child_node_count(struct device *dev); //获取设备的子节点个数
//产生一个for循环用于检查所有的子节点 #define device_for_each_child_node(dev, child) \ for (child = device_get_next_child_node(dev, NULL); child; \ child = device_get_next_child_node(dev, child))
//注意函数以"device"开头表示读取设备的属性, 以"fwnode"开头表示读取子节点的属性. 用于获取mynodes设备资源的驱动源码:
/* mydrv.c */
#include <linux/init.h> #include <linux/module.h> #include <linux/platform_device.h> #include <linux/property.h>
int myprobe(struct platform_device *pdev) { struct fwnode_handle *fwhandle; const char *str; u32 val;
//获取设备子节点的个数 printk("child node count : %d\n", device_get_child_node_count(&pdev->dev)); //获取设备属性autorepeat的值 printk("%d\n", device_property_read_bool(&pdev->dev, "autorepeat"));
//遍历设备的每个子节点 device_for_each_child_node(&pdev->dev, fwhandle) { //获取设备子节点的label属性值 fwnode_property_read_string(fwhandle, "label", &str); printk("label = %s\n", str); //获取设备子节点的code属性值 fwnode_property_read_u32(fwhandle, "code", &val); printk("code = %x\n", val); };
return 0; }
int myremove(struct platform_device *pdev) { printk("in myremove ...\n"); return 0; }
struct of_device_id ids[] = { {.compatible = "mynodes"}, {}, };
struct platform_driver mydrv = { .probe = myprobe, .remove = myremove,
.driver = { .owner = THIS_MODULE, .name = "mydrv" ,
.of_match_table = ids, }, };
module_platform_driver(mydrv); MODULE_LICENSE("GPL"); 1 2 编译驱动模块加载后的输出结果:
[ 419.424065] child node count : 2 [ 419.427429] 1 [ 419.429054] label = btn1 [ 419.431690] code = 11 [ 419.434000] label = btn2 [ 419.436623] code = 22 ————————————————