本文转载自：http://blog.csdn.net/fengyuwuzu0519/article/details/74352188
一、DTS编写语法
二、常用函数
设备树函数思路是：
uboot启动时将设备树地址传给内核，内核解析设备树，并创建设备，初始化相关属性，驱动中通过of_get_XXX函数去获取设备树加载时创建的设备。想要知道of函数做了什么，就去追踪这个函数最后调用了什么，同时也就知道了内核解析设备树的时候为我们创建了什么。
uboot启动时将设备树地址传给内核，内核解析设备树，并创建设备，初始化相关属性，驱动中通过of_get_XXX函数去获取设备树加载时创建的设备。想要知道of函数做了什么，就去追踪这个函数最后调用了什么，同时也就知道了内核解析设备树的时候为我们创建了什么。
（1）of_get_named_gpio
/**
* include/of_gpio.h
* of_get_named_gpio - 从设备树中提取gpio口
* @np - 设备节点指针
* @propname - 属性名
* @index - gpio口引脚标号
* 成功：得到GPIO口编号；失败：负数，绝对值是错误码
*/
int of_get_named_gpio(struct device_node *np, const char *propname, int index);
（2）gpio_to_irq
/**
* include/gpio.h
* PIN值转换为相应的IRQ值,中断编号可以传给request_irq()和free_irq()
* @gpio - gpio口引脚标号
* 成功：得到GPIO口编号
*/
static inline int gpio_to_irq(unsigned gpio)
（3）devm_request_any_context_irq
/**
* 注册中断
*/
devm_request_any_context_irq
（4）of_match_ptr
/**
* 匹配设备树上的参数，将设备int_demo_dt_ids与驱动int_demo_driver联系起来
* 系统会根据设备树种定义的compatible参数比较驱动中的int_demo_dt_ids中定义的 .compatible 参数
*/
of_match_ptr(int_demo_dt_ids)
例子：
static const struct of_device_id int_demo_dt_ids[] = {
{ .compatible = "tiny4412,interrupt_demo", },
{},
};
MODULE_DEVICE_TABLE(of, int_demo_dt_ids);
static struct platform_driver int_demo_driver = {
.driver = {
.name = "interrupt_demo",
.of_match_table = of_match_ptr(int_demo_dt_ids),
},
.probe = int_demo_probe,
.remove = int_demo_remove,
};
* include/of_gpio.h
* of_get_named_gpio - 从设备树中提取gpio口
* @np - 设备节点指针
* @propname - 属性名
* @index - gpio口引脚标号
* 成功：得到GPIO口编号；失败：负数，绝对值是错误码
*/
int of_get_named_gpio(struct device_node *np, const char *propname, int index);
（2）gpio_to_irq
/**
* include/gpio.h
* PIN值转换为相应的IRQ值,中断编号可以传给request_irq()和free_irq()
* @gpio - gpio口引脚标号
* 成功：得到GPIO口编号
*/
static inline int gpio_to_irq(unsigned gpio)
（3）devm_request_any_context_irq
/**
* 注册中断
*/
devm_request_any_context_irq
（4）of_match_ptr
/**
* 匹配设备树上的参数，将设备int_demo_dt_ids与驱动int_demo_driver联系起来
* 系统会根据设备树种定义的compatible参数比较驱动中的int_demo_dt_ids中定义的 .compatible 参数
*/
of_match_ptr(int_demo_dt_ids)
例子：
static const struct of_device_id int_demo_dt_ids[] = {
{ .compatible = "tiny4412,interrupt_demo", },
{},
};
MODULE_DEVICE_TABLE(of, int_demo_dt_ids);
static struct platform_driver int_demo_driver = {
.driver = {
.name = "interrupt_demo",
.of_match_table = of_match_ptr(int_demo_dt_ids),
},
.probe = int_demo_probe,
.remove = int_demo_remove,
};
（5）of_get_property
/*
*/drivers/of/base.c
* Find a property with a given name for a given node
* and return the value.
* 通过给定的设备节点和属性名字得到value。
*/
const void *of_get_property(const struct device_node *np, const char *name,
int *lenp)
{
struct property *pp = of_find_property(np, name, lenp);
return pp ? pp->value : NULL;
}
*/drivers/of/base.c
* Find a property with a given name for a given node
* and return the value.
* 通过给定的设备节点和属性名字得到value。
*/
const void *of_get_property(const struct device_node *np, const char *name,
int *lenp)
{
struct property *pp = of_find_property(np, name, lenp);
return pp ? pp->value : NULL;
}
（6）devm_pinctrl_get
获取一个pinctrl句柄，参数是dev是包含这个pin的device结构体即xxx这个设备的device
获取设备操作句柄（设备模型中的struct device）的pin control state holder（struct pinctrl）
/**
* struct devm_pinctrl_get() - Resource managed pinctrl_get()
* @dev: the device to obtain the handle for
*
* If there is a need to explicitly destroy the returned struct pinctrl,
* devm_pinctrl_put() should be used, rather than plain pinctrl_put().
*/
struct pinctrl *devm_pinctrl_get(struct device *dev)
（7）pinctrl_lookup_state
获取这个pin对应pin_state（引脚状态-turnon_tes/turnoff_tes）
/**
* pinctrl_lookup_state() - retrieves a state handle from a pinctrl handle
* @p: the pinctrl handle to retrieve the state from
* @name: the state name to retrieve
*/
struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p, const char *name)
（8）pinctrl_select_state
设置引脚为为某个stata -- turnon_tes/turnoff_tes
/**
* pinctrl_select_state() - select/activate/program a pinctrl state to HW
* @p: the pinctrl handle for the device that requests configuration
* @state: the state handle to select/activate/program
*/
int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
（9）of_get_named_gpio
得到GPIO的编号
./**
* include/of_gpio.h
* of_get_named_gpio - 从设备树中提取gpio口
* @np - 设备节点指针
* @propname - 属性名
* @index - gpio口引脚标号
* 成功：得到GPIO口编号int型；失败：负数，绝对值是错误码
*/
int of_get_named_gpio(struct device_node *np, const char *propname, int index);
of_get_named_gpio：此函数是解析设备树的函数，我们通过这个函数去解析设备树，tiny4412,int_gpio1 = <&gpx3 2 GPIO_ACTIVE_HIGH>;
跟踪下去会发现这个函数掉用了list = of_get_property(np, "tiny4412,int_gpio2", &size);设备树解析是创界了设备节点，现在通过这个函数去获取属性。
（10）devm_gpio_request_one
获取一个GPIO并初始化属性
/**
* devm_gpio_request_one - request a single GPIO with initial setup
* @dev: device to request for
* @gpio: the GPIO number
* @flags: GPIO configuration as specified by GPIOF_*
* @label: a literal description string of this GPIO
*/
int devm_gpio_request_one(struct device *dev, unsigned gpio,
unsigned long flags, const char *label)
获取设备操作句柄（设备模型中的struct device）的pin control state holder（struct pinctrl）
/**
* struct devm_pinctrl_get() - Resource managed pinctrl_get()
* @dev: the device to obtain the handle for
*
* If there is a need to explicitly destroy the returned struct pinctrl,
* devm_pinctrl_put() should be used, rather than plain pinctrl_put().
*/
struct pinctrl *devm_pinctrl_get(struct device *dev)
（7）pinctrl_lookup_state
获取这个pin对应pin_state（引脚状态-turnon_tes/turnoff_tes）
/**
* pinctrl_lookup_state() - retrieves a state handle from a pinctrl handle
* @p: the pinctrl handle to retrieve the state from
* @name: the state name to retrieve
*/
struct pinctrl_state *pinctrl_lookup_state(struct pinctrl *p, const char *name)
（8）pinctrl_select_state
设置引脚为为某个stata -- turnon_tes/turnoff_tes
/**
* pinctrl_select_state() - select/activate/program a pinctrl state to HW
* @p: the pinctrl handle for the device that requests configuration
* @state: the state handle to select/activate/program
*/
int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)
（9）of_get_named_gpio
得到GPIO的编号
./**
* include/of_gpio.h
* of_get_named_gpio - 从设备树中提取gpio口
* @np - 设备节点指针
* @propname - 属性名
* @index - gpio口引脚标号
* 成功：得到GPIO口编号int型；失败：负数，绝对值是错误码
*/
int of_get_named_gpio(struct device_node *np, const char *propname, int index);
of_get_named_gpio：此函数是解析设备树的函数，我们通过这个函数去解析设备树，tiny4412,int_gpio1 = <&gpx3 2 GPIO_ACTIVE_HIGH>;
跟踪下去会发现这个函数掉用了list = of_get_property(np, "tiny4412,int_gpio2", &size);设备树解析是创界了设备节点，现在通过这个函数去获取属性。
（10）devm_gpio_request_one
获取一个GPIO并初始化属性
/**
* devm_gpio_request_one - request a single GPIO with initial setup
* @dev: device to request for
* @gpio: the GPIO number
* @flags: GPIO configuration as specified by GPIOF_*
* @label: a literal description string of this GPIO
*/
int devm_gpio_request_one(struct device *dev, unsigned gpio,
unsigned long flags, const char *label)