linux设备树的of_类的API寻找
授人以鱼不如授人以渔，那么，拿人以鱼不如学人以渔
base
作用：基本api
文件：drivers/of/base.c基本的api
例子：
/** 在设备树的设备节点中通过name来寻找
* of_find_node_by_name - Find a node by its "name" property
* @from: The node to start searching from or NULL, the node
* you pass will not be searched, only the next one
* will; typically, you pass what the previous call
* returned. of_node_put() will be called on it
* @name: The name string to match against
*
* Returns a node pointer with refcount incremented, use
* of_node_put() on it when done.
*/
struct device_node *of_find_node_by_name(struct device_node *from,
const char *name)/** 在设备树的设备节点中通过path来寻找
* of_find_node_by_path - Find a node matching a full OF path
* @path: The full path to match
*
* Returns a node pointer with refcount incremented, use
* of_node_put() on it when done.
*/
struct device_node *of_find_node_by_path(const char *path)/** 检查设备是否可用
* of_device_is_available - check if a device is available for use
*
* @device: Node to check for availability
*
* Returns 1 if the status property is absent or set to "okay" or "ok",
* 0 otherwise
*/
int of_device_is_available(const struct device_node *device)/** 读一个 u64 的整型变量
* of_property_read_u64 - Find and read a 64 bit integer from a property
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @out_value: pointer to return value, modified only if return value is 0.
*
* Search for a property in a device node and read a 64-bit value from
* it. Returns 0 on success, -EINVAL if the property does not exist,
* -ENODATA if property does not have a value, and -EOVERFLOW if the
* property data isn't large enough.
*
* The out_value is modified only if a valid u64 value can be decoded.
*/
int of_property_read_u64(const struct device_node *np, const char *propname,
u64 *out_value)/** 读字符串变量
* of_property_read_string - Find and read a string from a property
* @np: device node from which the property value is to be read.
* @propname: name of the property to be searched.
* @out_string: pointer to null terminated return string, modified only if
* return value is 0.
*
* Search for a property in a device tree node and retrieve a null
* terminated string value (pointer to data, not a copy). Returns 0 on
* success, -EINVAL if the property does not exist, -ENODATA if property
* does not have a value, and -EILSEQ if the string is not null-terminated
* within the length of the property data.
*
* The out_string pointer is modified only if a valid string can be decoded.
*/
int of_property_read_string(struct device_node *np, const char *propname,
const char **out_string)
address
作用：与地址有关的操作
文件：drivers/of/address.c
例子：
/** 内存映射
* of_iomap - Maps the memory mapped IO for a given device_node
* @device: the device whose io range will be mapped
* @index: index of the io range
*
* Returns a pointer to the mapped memory
*/
void __iomem *of_iomap(struct device_node *np, int index)/**
* of_address_to_resource - Translate device tree address and return as resource
*
* Note that if your address is a PIO address, the conversion will fail if
* the physical address can't be internally converted to an IO token with
* pci_address_to_pio(), that is because it's either called to early or it
* can't be matched to any host bridge IO space
*/
int of_address_to_resource(struct device_node *dev, int index,
struct resource *r)
device
作用：与设备有关的操作
文件：drviers/of/device.c
/**
* of_match_device - Tell if a struct device matches an of_device_id list
* @ids: array of of device match structures to search in
* @dev: the of device structure to match against
*
* Used by a driver to check whether an platform_device present in the
* system is in its list of supported devices.
*/
const struct of_device_id *of_match_device(const struct of_device_id *matches,
const struct device *dev)
fdt
作用：用来处理设备树（Flattened Device Tree）的数据格式
文件：drviers/of/fdt.c
/**
* of_fdt_is_compatible - Return true if given node from the given blob has
* compat in its compatible list
* @blob: A device tree blob
* @node: node to test
* @compat: compatible string to compare with compatible list.
*
* On match, returns a non-zero value with smaller values returned for more
* specific compatible values.
*/
int of_fdt_is_compatible(struct boot_param_header *blob,
unsigned long node, const char *compat)
irq
作用：处理中断操作
文件：drviers/of/irq.c
/**
* of_irq_init - Scan and init matching interrupt controllers in DT
* @matches: 0 terminated array of nodes to match and init function to call
*
* This function scans the device tree for matching interrupt controller nodes,
* and calls their initialization functions in order with parents first.
*/
void __init of_irq_init(const struct of_device_id *matches)/**
* of_irq_count - Count the number of IRQs a node uses
* @dev: pointer to device tree node
*/
int of_irq_count(struct device_node *dev)
另外一些
以上只是举例，不代表最重要，还有一些其他的操作，全部在路径drivers/of下面
有：i2c处理相关、mtd处理相关、网络相关、pci相关、平台相关等。
罗列一下：
address.c
base.c
device.c
fdt.c
irq.c
of_i2c.c
of_mdio.c
of_mtd.c
of_net.c
of_pci.c
of_pci_irq.c
platform.c
总结
找对方向，一切都好说
