接前一篇文章：Linux网络驱动之Fixed-Link（6）
本文内容参考：
GMAC网卡Fixed-Link模式 - StepForwards - 博客园
RTL8367RB的国产P2P替代方案用JL6107-PC的可行性及实现方法-CSDN博客
linux phy处理流程一:探测phy设备_phy link过程-CSDN博客
Linux 网络驱动-MAC、PHY层驱动框架(三)_ethernet-phy-ieee802.3-c22-CSDN博客
特此致谢！
三、深入了解
4. Linux内核中Fixed-Link的相关内容
（2）PHY驱动（driver）匹配
上一回继续讲解of_phy_get_and_connect函数，讲解了of_phy_is_fixed_link函数返回true的情况，本回讲解of_phy_is_fixed_link函数返回false的情况。为了便于理解和回顾，再次贴出of_phy_get_and_connect函数代码，在drivers/net/mdio/of_mdio.c中，如下：
cpp
/**
* of_phy_get_and_connect
* - Get phy node and connect to the phy described in the device tree
* @dev: pointer to net_device claiming the phy
* @np: Pointer to device tree node for the net_device claiming the phy
* @hndlr: Link state callback for the network device
*
* If successful, returns a pointer to the phy_device with the embedded
* struct device refcount incremented by one, or NULL on failure. The
* refcount must be dropped by calling phy_disconnect() or phy_detach().
*/
struct phy_device *of_phy_get_and_connect(struct net_device *dev,
struct device_node *np,
void (*hndlr)(struct net_device *))
{
phy_interface_t iface;
struct device_node *phy_np;
struct phy_device *phy;
int ret;
ret = of_get_phy_mode(np, &iface);
if (ret)
return NULL;
if (of_phy_is_fixed_link(np)) {
ret = of_phy_register_fixed_link(np);
if (ret < 0) {
netdev_err(dev, "broken fixed-link specification\n");
return NULL;
}
phy_np = of_node_get(np);
} else {
phy_np = of_parse_phandle(np, "phy-handle", 0);
if (!phy_np)
return NULL;
}
phy = of_phy_connect(dev, phy_np, hndlr, 0, iface);
of_node_put(phy_np);
return phy;
}
EXPORT_SYMBOL(of_phy_get_and_connect);of_phy_is_fixed_link函数返回false，也就是在DTS文件中没有找到Fixed-Link相关结点时，则走else分支。代码片段如下：
cpp
else {
phy_np = of_parse_phandle(np, "phy-handle", 0);
if (!phy_np)
return NULL;
}else分支中，主要是调用了of_parse_phandle函数，处理phy结点。of_parse_handle函数在include/linux/of.h中，代码如下：
cpp
/**
* of_parse_phandle - Resolve a phandle property to a device_node pointer
* @np: Pointer to device node holding phandle property
* @phandle_name: Name of property holding a phandle value
* @index: For properties holding a table of phandles, this is the index into
* the table
*
* Return: The device_node pointer with refcount incremented. Use
* of_node_put() on it when done.
*/
static inline struct device_node *of_parse_phandle(const struct device_node *np,
const char *phandle_name,
int index)
{
struct of_phandle_args args;
if (__of_parse_phandle_with_args(np, phandle_name, NULL, 0,
index, &args))
return NULL;
return args.np;
}看一下函数注释，of_parse_phandle函数的作用是，将phandle属性解析为device_node指针。该函数和上一回的of_node_get函数类似，也是由struct device *得到struct device_node *。
参数说明：
- np：指向包含phandle属性的设备节点的指针
- phandle_name：持有phandle值的属性名称
- index：对于持有phandles表的属性，这是表中的索引
返回值：
带有refcount已递增的device_node指针。完成后对其使用of_node_put()。
__of_parse_phandle_with_args函数在drivers/of/base.c中，代码如下：
cpp
int __of_parse_phandle_with_args(const struct device_node *np,
const char *list_name,
const char *cells_name,
int cell_count, int index,
struct of_phandle_args *out_args)
{
struct of_phandle_iterator it;
int rc, cur_index = 0;
if (index < 0)
return -EINVAL;
/* Loop over the phandles until all the requested entry is found */
of_for_each_phandle(&it, rc, np, list_name, cells_name, cell_count) {
/*
* All of the error cases bail out of the loop, so at
* this point, the parsing is successful. If the requested
* index matches, then fill the out_args structure and return,
* or return -ENOENT for an empty entry.
*/
rc = -ENOENT;
if (cur_index == index) {
if (!it.phandle)
goto err;
if (out_args) {
int c;
c = of_phandle_iterator_args(&it,
out_args->args,
MAX_PHANDLE_ARGS);
out_args->np = it.node;
out_args->args_count = c;
} else {
of_node_put(it.node);
}
/* Found it! return success */
return 0;
}
cur_index++;
}
/*
* Unlock node before returning result; will be one of:
* -ENOENT : index is for empty phandle
* -EINVAL : parsing error on data
*/
err:
of_node_put(it.node);
return rc;
}
EXPORT_SYMBOL(__of_parse_phandle_with_args);回到of_phy_get_and_connect函数中：
cpp
/**
* of_phy_get_and_connect
* - Get phy node and connect to the phy described in the device tree
* @dev: pointer to net_device claiming the phy
* @np: Pointer to device tree node for the net_device claiming the phy
* @hndlr: Link state callback for the network device
*
* If successful, returns a pointer to the phy_device with the embedded
* struct device refcount incremented by one, or NULL on failure. The
* refcount must be dropped by calling phy_disconnect() or phy_detach().
*/
struct phy_device *of_phy_get_and_connect(struct net_device *dev,
struct device_node *np,
void (*hndlr)(struct net_device *))
{
phy_interface_t iface;
struct device_node *phy_np;
struct phy_device *phy;
int ret;
ret = of_get_phy_mode(np, &iface);
if (ret)
return NULL;
if (of_phy_is_fixed_link(np)) {
ret = of_phy_register_fixed_link(np);
if (ret < 0) {
netdev_err(dev, "broken fixed-link specification\n");
return NULL;
}
phy_np = of_node_get(np);
} else {
phy_np = of_parse_phandle(np, "phy-handle", 0);
if (!phy_np)
return NULL;
}
phy = of_phy_connect(dev, phy_np, hndlr, 0, iface);
of_node_put(phy_np);
return phy;
}
EXPORT_SYMBOL(of_phy_get_and_connect);接下来调用of_phy_connect函数。其也在drivers/net/mdio/of_mdio.c中，代码如下：
cpp
/**
* of_phy_connect - Connect to the phy described in the device tree
* @dev: pointer to net_device claiming the phy
* @phy_np: Pointer to device tree node for the PHY
* @hndlr: Link state callback for the network device
* @flags: flags to pass to the PHY
* @iface: PHY data interface type
*
* If successful, returns a pointer to the phy_device with the embedded
* struct device refcount incremented by one, or NULL on failure. The
* refcount must be dropped by calling phy_disconnect() or phy_detach().
*/
struct phy_device *of_phy_connect(struct net_device *dev,
struct device_node *phy_np,
void (*hndlr)(struct net_device *), u32 flags,
phy_interface_t iface)
{
struct phy_device *phy = of_phy_find_device(phy_np);
int ret;
if (!phy)
return NULL;
phy->dev_flags |= flags;
ret = phy_connect_direct(dev, phy, hndlr, iface);
/* refcount is held by phy_connect_direct() on success */
put_device(&phy->mdio.dev);
return ret ? NULL : phy;
}
EXPORT_SYMBOL(of_phy_connect);这就回到了前文书（Linux网络驱动之Fixed-Link（5）-CSDN博客）的起点：
对于of_phy_connect函数的解析，请看下回。