gpio子系统和pinctrl子系统（二）

本文主要是介绍gpio子系统和pinctrl子系统（二），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

转自http://blog.rongpmcu.com/gpiozi-xi-tong-he-pinctrlzi-xi-tong-zhong/

pinctrl子系统核心实现分析

pinctrl子系统的内容在drivers/pinctrl文件夹下，主要文件有(建议先看看pinctrl内核文档Documentation/pinctrl.txt)：
core.c
devicetree.c
pinconf.c
pinmux.c
pinctrl-xxx.c

core.c为pinctrl的核心代码，实现了pinctrl框架，pinmux.c和pinconf.c基于core实现了对pinmux和pinconf的支持，pinctrl-xxx.c为厂商相关的pinctrl实现（又是苦逼的bsp工程师^_^），当然有些厂商还未采用pinctrl机制，因此就没有对应的实现。最后说一句，pinctrl的实现不许用我们在驱动里调用任何它提供的api，所有的pinctrl动作都是在通用内核代码里完成了，对于驱动工程师是透明的。驱动工程师只需要通过设备树文件就能掌控整个系统的pin管理了，后面分析的过程会证实这一点。

pinctrl在代码层级只与bsp工程师有关，他们需要调用pinctrl api pinctrl_register注册。先引用一张网上截图：
pinctrl子系统框架对于驱动工程师，只需要通过设备树文件就可以起到配置整个系统pin的目的。有几个概念先理一下，功能和组，功能就是指uart、i2c、spi等这些，组是pin的集合，我们都知道现在的soc的pin中，经常会遇到一个功能可以由不同的pin集合（即组）配置，当然同一时间只能选一个pin集合，因此，当我们要用某个功能的时候，需要告诉它func以及哪一组。下面开始分析pinctrl_register：

struct pinctrl_dev *pinctrl_register(struct pinctrl_desc *pctldesc,  struct device *dev, void *driver_data)
{struct pinctrl_dev *pctldev;int ret;if (!pctldesc)return NULL;if (!pctldesc->name)return NULL;//一般只有pinctrl　chip driver需要调用pinctrl_register，pctldev就是软件上pinctrl的抽象pctldev = kzalloc(sizeof(*pctldev), GFP_KERNEL);if (pctldev == NULL) {dev_err(dev, "failed to alloc struct pinctrl_dev\n");return NULL;}/* Initialize pin control device struct *///初始化一些成员，后面会遇到它们的pctldev->owner = pctldesc->owner;pctldev->desc = pctldesc;pctldev->driver_data = driver_data;//pin_desc_tree用于存放所有的pin信息，由后面即将分析的pinctrl_register_pins来填充//所有pin信息来源于输入参数pctldesc，也就是说每个pinctrl　chip driver的实现者需要告诉pinctrl//子系统该pinctrl chip所有的pin信息INIT_RADIX_TREE(&pctldev->pin_desc_tree, GFP_KERNEL);//这个由gpio子系统填充信息，还记得of_gpiochip_add_pin_range吧^_^最后总结的时候再结合gpio子系统一起看看这部分INIT_LIST_HEAD(&pctldev->gpio_ranges);pctldev->dev = dev;mutex_init(&pctldev->mutex);/* check core ops for sanity *///pinctrl_ops是pinctrl chip driver必须要实现的一组回调集合，后面在用到它里面的api时再详细讲解if (pinctrl_check_ops(pctldev)) {dev_err(dev, "pinctrl ops lacks necessary functions\n");goto out_err;}/* If we're implementing pinmuxing, check the ops for sanity *///如果提供了pinmux　ops，检查下是否合法if (pctldesc->pmxops) {if (pinmux_check_ops(pctldev))goto out_err;}/* If we're implementing pinconfig, check the ops for sanity *///如果提供了pinconf　ops，检查下是否合法if (pctldesc->confops) {if (pinconf_check_ops(pctldev))goto out_err;}/* Register all the pins */dev_dbg(dev, "try to register %d pins ...\n",  pctldesc->npins);//第一个核心操作，后面详细分析　　　　---------> 1ret = pinctrl_register_pins(pctldev, pctldesc->pins, pctldesc->npins);if (ret) {dev_err(dev, "error during pin registration\n");pinctrl_free_pindescs(pctldev, pctldesc->pins,pctldesc->npins);goto out_err;}mutex_lock(&pinctrldev_list_mutex);//将pctldev加入到全局链表list_add_tail(&pctldev->node, &pinctrldev_list);mutex_unlock(&pinctrldev_list_mutex);//这是第二个核心操作，往往pinctrl设备本身也需要做一些配置，这个函数就是用于处理这个功能---------> 2pctldev->p = pinctrl_get(pctldev->dev);if (!IS_ERR(pctldev->p)) {//如果pinctrl设备提供了default状态，设置为default状态pctldev->hog_default =pinctrl_lookup_state(pctldev->p, PINCTRL_STATE_DEFAULT);if (IS_ERR(pctldev->hog_default)) {dev_dbg(dev, "failed to lookup the default state\n");} else {//设置为default状态if (pinctrl_select_state(pctldev->p,pctldev->hog_default))dev_err(dev,"failed to select default state\n");}//如果pinctrl设备提供了sleep状态，获取它，以后再用pctldev->hog_sleep =pinctrl_lookup_state(pctldev->p,PINCTRL_STATE_SLEEP);if (IS_ERR(pctldev->hog_sleep))dev_dbg(dev, "failed to lookup the sleep state\n");}//和调试相关，先忽略吧pinctrl_init_device_debugfs(pctldev);return pctldev;out_err:  mutex_destroy(&pctldev->mutex);kfree(pctldev);return NULL;
}

总结一下，pinctrl_register主要做了以下工作：
1. 分配pctldev数据结构，并添加到全局链表pinctrldev_list中
2. 填充pctldev，根据pctldesc里的pin信息注册所有的pin信息到pctldev里的pin_desc_tree管理起来，
3. 如果该pinctrl对应的设备树里有描述它自己的pin配置信息，那么解析它，并设置为default状态。这一部分是任何一个用到pinctrl设备都会进行的动作（解析、设置状态）
4. 初始化调试相关的东西

下面先看看pinctrl_register_pins的过程：

static int pinctrl_register_pins(struct pinctrl_dev *pctldev,  struct pinctrl_pin_desc const *pins,unsigned num_descs)
{unsigned i;int ret = 0;for (i = 0; i < num_descs; i++) {//遍历传入的所有pin的数据结构，一个个处理它们//pinctrl driver会传入所有的pin管脚及对应的名称ret = pinctrl_register_one_pin(pctldev,pins[i].number, pins[i].name);if (ret)return ret;}return 0;
}static int pinctrl_register_one_pin(struct pinctrl_dev *pctldev,  unsigned number, const char *name)
{struct pin_desc *pindesc;//查看是否已经存在了pindesc = pin_desc_get(pctldev, number);if (pindesc != NULL) {pr_err("pin %d already registered on %s\n", number,pctldev->desc->name);return -EINVAL;}//分配一个pinctrl子系统用于管理pin的数据结构pindesc = kzalloc(sizeof(*pindesc), GFP_KERNEL);if (pindesc == NULL) {dev_err(pctldev->dev, "failed to alloc struct pin_desc\n");return -ENOMEM;}/* Set owner *///指定该pin的拥有者pindesc->pctldev = pctldev;/* Copy basic pin info */if (name) {//如果指定了名字，那么好吧，就用你了pindesc->name = name;} else {//如果没有指定名字，用默认的格式组合一个pindesc->name = kasprintf(GFP_KERNEL, "PIN%u", number);if (pindesc->name == NULL) {kfree(pindesc);return -ENOMEM;}pindesc->dynamic_name = true;}//将该pin添加到pctldev里管理起来radix_tree_insert(&pctldev->pin_desc_tree, number, pindesc);pr_debug("registered pin %d (%s) on %s\n",number, pindesc->name, pctldev->desc->name);return 0;
}

下面开始分析第二个核心部分pinctrl_get，注意，这部分是任何一个用到pinctrl设备都会进行的动作（解析、设置状态），所以还必须弄清楚它，它主要的作用就是通过解析该设备的pinctrl信息生成一个pinctrl数据结构，用于管理该设备的pin信息，如有哪些状态、每个状态有哪些设置（设置包括pinmux和pinconf两种，有些设备只用需要pinmux，有些需要pinmux和pinconf）

struct pinctrl *pinctrl_get(struct device *dev)  
{struct pinctrl *p;if (WARN_ON(!dev))return ERR_PTR(-EINVAL);/** See if somebody else (such as the device core) has already* obtained a handle to the pinctrl for this device. In that case,* return another pointer to it.*///如果已经有其他模块get了，那么pinctrl肯定已经创建好了，直接返回吧p = find_pinctrl(dev);if (p != NULL) {dev_dbg(dev, "obtain a copy of previously claimed pinctrl\n");kref_get(&p->users);return p;}//否则，创建一个pinctrl用于管理该设备本身的pin信息return create_pinctrl(dev);
}

继续看解析的过程，通过看懂这部分，我们应该就很清楚设备树里需要怎么配置，怎么对整个系统的pin配置起作用的

static struct pinctrl *create_pinctrl(struct device *dev)  
{struct pinctrl *p;const char *devname;struct pinctrl_maps *maps_node;int i;struct pinctrl_map const *map;int ret;/** create the state cookie holder struct pinctrl for each* mapping, this is what consumers will get when requesting* a pin control handle with pinctrl_get()*/p = kzalloc(sizeof(*p), GFP_KERNEL);if (p == NULL) {dev_err(dev, "failed to alloc struct pinctrl\n");return ERR_PTR(-ENOMEM);}p->dev = dev;//每个需要管理的设备都会有对应的pinctrl，每个设备也会有多个状态，如default、sleep等等（内核//默认定义了一些，自己也可以随意定义），每个状态又有可能有多种设置。这个需要自己慢慢理解^_^//这里的states成员就是用于存放所有的状态的INIT_LIST_HEAD(&p->states);//这里的dt_maps就是用于存放所有的设置的INIT_LIST_HEAD(&p->dt_maps);//又是一个复杂的函数，后面分析，它主要用于解析设备树里的信息，生成该设备对应的maps（设置）ret = pinctrl_dt_to_map(p);if (ret < 0) {kfree(p);return ERR_PTR(ret);}devname = dev_name(dev);mutex_lock(&pinctrl_maps_mutex);/* Iterate over the pin control maps to locate the right ones *///遍历所有的的设置，这里遍历的是全局的maps链表，因为它要用到//pinctrl_map结构，而p->dt_maps里的不是该类型for_each_maps(maps_node, i, map) {/* Map must be for this device *///检查是否属于俺的设置if (strcmp(map->dev_name, devname))continue;//将该设置加入到pinctrl中，也许有人会奇怪，前面的dt_maps不是已经包含了该设备的所有设置了么，//其实这里会对每个设置做进一步处理，然后放入到p中，后面分析ret = add_setting(p, map);/** At this point the adding of a setting may:** - Defer, if the pinctrl device is not yet available* - Fail, if the pinctrl device is not yet available,*   AND the setting is a hog. We cannot defer that, since*   the hog will kick in immediately after the device*   is registered.** If the error returned was not -EPROBE_DEFER then we* accumulate the errors to see if we end up with* an -EPROBE_DEFER later, as that is the worst case.*/if (ret == -EPROBE_DEFER) {pinctrl_free(p, false);mutex_unlock(&pinctrl_maps_mutex);return ERR_PTR(ret);}}mutex_unlock(&pinctrl_maps_mutex);if (ret < 0) {/* If some other error than deferral occured, return here */pinctrl_free(p, false);return ERR_PTR(ret);}kref_init(&p->users);/* Add the pinctrl handle to the global list */mutex_lock(&pinctrl_list_mutex);//将每个设备用于控制pin的结构也放到一个全局链表中list_add_tail(&p->node, &pinctrl_list);mutex_unlock(&pinctrl_list_mutex);return p;
}

先总结下create_pinctrl：
1. 创建一个pinctrl，将它加入到全局的pinctrl链表
2. 解析该设备的说有设备树信息，将解析的状态挂到states里，解析的设置挂到dt_maps（当然，设置同时也挂到全局的maps里去了）

实在不想贴代码了，不过不贴又不好解释清楚^_^　继续上pinctrl_dt_to_map吧，它就是实现了上面总结的第二点：

int pinctrl_dt_to_map(struct pinctrl *p)  
{struct device_node *np = p->dev->of_node;int state, ret;char *propname;struct property *prop;const char *statename;const __be32 *list;int size, config;phandle phandle;struct device_node *np_config;/* CONFIG_OF enabled, p->dev not instantiated from DT */if (!np) {if (of_have_populated_dt())dev_dbg(p->dev,"no of_node; not parsing pinctrl DT\n");return 0;}/* We may store pointers to property names within the node */of_node_get(np);/* For each defined state ID */for (state = 0; ; state++) {/* Retrieve the pinctrl-* property *///pinctrl子系统规定了几个属性，如pinctrl-n，用于指定一个状态对应的设置，从0开始        propname = kasprintf(GFP_KERNEL, "pinctrl-%d", state);//查找pinctrl-n属性prop = of_find_property(np, propname, &size);kfree(propname);if (!prop)break;//value对应的就是该状态对应的设置（可能有多个），后面会处理它list = prop->value;size /= sizeof(*list);/* Determine whether pinctrl-names property names the state *///读pinctrl-names属性，也属于pinctrl子系统规定的属性，用于指定每个状态的名字，一一对应的ret = of_property_read_string_index(np, "pinctrl-names",state, &statename);/** If not, statename is just the integer state ID. But rather* than dynamically allocate it and have to free it later,* just point part way into the property name for the string.*/if (ret < 0) {/* strlen("pinctrl-") == 8 *///如果美誉pinctrl-names属性，那么状态名就是indexstatename = prop->name + 8;}/* For every referenced pin configuration node in it *///一个一个处理设置for (config = 0; config < size; config++) {//第一个成员规定为配置节点（属于pinctrl的子节点）的引用，因此通过它可以找到该配置节点phandle = be32_to_cpup(list++);/* Look up the pin configuration node */np_config = of_find_node_by_phandle(phandle);if (!np_config) {dev_err(p->dev,"prop %s index %i invalid phandle\n",prop->name, config);ret = -EINVAL;goto err;}/* Parse the node *///找到对应的配置节点了，那么就解析那个配置节点到该设备的这个状态的这个设置中吧，后面继续贴　哎ret = dt_to_map_one_config(p, statename, np_config);of_node_put(np_config);if (ret < 0)goto err;}/* No entries in DT? Generate a dummy state table entry */if (!size) {ret = dt_remember_dummy_state(p, statename);if (ret < 0)goto err;}}return 0;err:  pinctrl_dt_free_maps(p);return ret;
}

继续看dt_to_map_one_config：

static int dt_to_map_one_config(struct pinctrl *p, const char *statename,  struct device_node *np_config)
{struct device_node *np_pctldev;struct pinctrl_dev *pctldev;const struct pinctrl_ops *ops;int ret;struct pinctrl_map *map;unsigned num_maps;/* Find the pin controller containing np_config */np_pctldev = of_node_get(np_config);for (;;) {//找该节点的父节点，就是pinctrl设备啦，我们得通过它获取pctldev，毕竟只有它才有啊np_pctldev = of_get_next_parent(np_pctldev);if (!np_pctldev || of_node_is_root(np_pctldev)) {dev_info(p->dev, "could not find pctldev for node %s, deferring probe\n",np_config->full_name);of_node_put(np_pctldev);/* OK let's just assume this will appear later then */return -EPROBE_DEFER;}pctldev = get_pinctrl_dev_from_of_node(np_pctldev);if (pctldev)//拿到就跳出break;/* Do not defer probing of hogs (circular loop) */if (np_pctldev == p->dev->of_node) {of_node_put(np_pctldev);return -ENODEV;}}of_node_put(np_pctldev);/** Call pinctrl driver to parse device tree node, and* generate mapping table entries*/ops = pctldev->desc->pctlops;//这里就用到了pinctrl_register注册时pctlops里的dt_node_to_map回调函数了if (!ops->dt_node_to_map) {dev_err(p->dev, "pctldev %s doesn't support DT\n",dev_name(pctldev->dev));return -ENODEV;}//调用它，靠它来解析出这个配置节点，毕竟格式只有对应的pinctrl driver最清楚ret = ops->dt_node_to_map(pctldev, np_config, &map, &num_maps);if (ret < 0)return ret;/* Stash the mapping table chunk away for later use *///将解析出来的设置添加到pctldev的dt_maps中，也会加到全局的maps中啦，这里就不再深入分析了，自己都觉得太啰嗦了return dt_remember_or_free_map(p, statename, pctldev, map, num_maps);
}

继续看add_setting：

static int add_setting(struct pinctrl *p, struct pinctrl_map const *map)  
{struct pinctrl_state *state;struct pinctrl_setting *setting;int ret;//前面只是解析出了所有的设置，这里就将所有的设置按状态归类起来，如果状态还没创建，就创建一个state = find_state(p, map->name);if (!state)state = create_state(p, map->name);if (IS_ERR(state))return PTR_ERR(state);if (map->type == PIN_MAP_TYPE_DUMMY_STATE)return 0;//分配一个设置数据结构setting = kzalloc(sizeof(*setting), GFP_KERNEL);if (setting == NULL) {dev_err(p->dev,"failed to alloc struct pinctrl_setting\n");return -ENOMEM;}//设置的类型setting->type = map->type;//设置所属的pctldevsetting->pctldev = get_pinctrl_dev_from_devname(map->ctrl_dev_name);if (setting->pctldev == NULL) {kfree(setting);/* Do not defer probing of hogs (circular loop) */if (!strcmp(map->ctrl_dev_name, map->dev_name))return -ENODEV;/** OK let us guess that the driver is not there yet, and* let's defer obtaining this pinctrl handle to later...*/dev_info(p->dev, "unknown pinctrl device %s in map entry, deferring probe",map->ctrl_dev_name);return -EPROBE_DEFER;}//设置名字setting->dev_name = map->dev_name;switch (map->type) {//根据设置的类型处理设置，因为设置可以表示mux功能，也可以表示conf功能case PIN_MAP_TYPE_MUX_GROUP://如果是mux功能的设置，调用mux模块处理ret = pinmux_map_to_setting(map, setting);break;case PIN_MAP_TYPE_CONFIGS_PIN:case PIN_MAP_TYPE_CONFIGS_GROUP://如果是mux功能的设置，调用conf模块处理ret = pinconf_map_to_setting(map, setting);break;default:ret = -EINVAL;break;}if (ret < 0) {kfree(setting);return ret;}//将设置放入状态链表归类list_add_tail(&setting->node, &state->settings);return 0;
}

下面分别分析pinmux_map_to_setting和pinconf_map_to_setting，先pinmux_map_to_setting，它是和pinmux相关，对应pinmux.c文件，里面也会用到pinmux_ops：

int pinmux_map_to_setting(struct pinctrl_map const *map,  struct pinctrl_setting *setting)
{struct pinctrl_dev *pctldev = setting->pctldev;const struct pinmux_ops *pmxops = pctldev->desc->pmxops;char const * const *groups;unsigned num_groups;int ret;const char *group;int i;//如果在register的时候没有指定pinmux_ops，那么该函数什么都不做，出错返回if (!pmxops) {dev_err(pctldev->dev, "does not support mux function\n");return -EINVAL;}//现在就是pinmux_ops作用的时候啦！里面会以从0开始的索引不停的调用//pinmux_ops里的get_function_name来获取对应的名字，然后和前面解析设备树过程解析出来的名字做匹配//直到找到或到末尾，返回该索引。这个索引与功能之间的关系由pinctrl　bsp实现者负责ret = pinmux_func_name_to_selector(pctldev, map->data.mux.function);if (ret < 0) {dev_err(pctldev->dev, "invalid function %s in map table\n",map->data.mux.function);return ret;}//保存该索引setting->data.mux.func = ret;//调用pmxops的get_function_groups获取该索引对应的组（可能存在多个，前面已经说过，一个功能可以由多个组实现，同一时间只能选一个组）ret = pmxops->get_function_groups(pctldev, setting->data.mux.func,&groups, &num_groups);if (ret < 0) {dev_err(pctldev->dev, "can't query groups for function %s\n",map->data.mux.function);return ret;}if (!num_groups) {dev_err(pctldev->dev,"function %s can't be selected on any group\n",map->data.mux.function);return -EINVAL;}//如果设备树里有直接指定组，那么就会以指定的组为默认选择if (map->data.mux.group) {bool found = false;group = map->data.mux.group;//当然，也还是要校验下，组是否有效for (i = 0; i < num_groups; i++) {if (!strcmp(group, groups[i])) {found = true;break;}}if (!found) {dev_err(pctldev->dev,"invalid group \"%s\" for function \"%s\"\n",group, map->data.mux.function);return -EINVAL;}} else {//如果没有指定，那么就用第一个组咯group = groups[0];}//根据选定的组，获取该组的信息，返回的是该组对应的索引，这里会调用pmxops的get_group_name，操作//过程和前面的pinmux_func_name_to_selector类似ret = pinctrl_get_group_selector(pctldev, group);if (ret < 0) {dev_err(pctldev->dev, "invalid group %s in map table\n",map->data.mux.group);return ret;}//保存该组索引setting->data.mux.group = ret;return 0;
}

继续pinconf_map_to_setting吧，它是和pinconf相关，对应pinconf.c文件，但里面还没用pinconf_ops，后面才会用到：

int pinconf_map_to_setting(struct pinctrl_map const *map,  struct pinctrl_setting *setting)
{struct pinctrl_dev *pctldev = setting->pctldev;int pin;switch (setting->type) {//该设置到底是什么类型，是pinctrl driver回调dt_node_to_map里解析的//配置有两种类型，一种是一个pin一个pin的配置，一种是将一些pin的配置组合为一个组，指定某个组就会采用那个组里的所有的pin的配置case PIN_MAP_TYPE_CONFIGS_PIN://根据设备树里指定的pin名字获取它对应的pin号pin = pin_get_from_name(pctldev,map->data.configs.group_or_pin);if (pin < 0) {dev_err(pctldev->dev, "could not map pin config for \"%s\"",map->data.configs.group_or_pin);return pin;}//将该设置对应的pin号保存起来setting->data.configs.group_or_pin = pin;break;case PIN_MAP_TYPE_CONFIGS_GROUP://根据设备树指定的pin组获取它对应的group号pin = pinctrl_get_group_selector(pctldev,map->data.configs.group_or_pin);if (pin < 0) {dev_err(pctldev->dev, "could not map group config for \"%s\"",map->data.configs.group_or_pin);return pin;}//将该设置对应的group号保存起来setting->data.configs.group_or_pin = pin;break;default:return -EINVAL;}//保存所有其他用于配置的信息setting->data.configs.num_configs = map->data.configs.num_configs;setting->data.configs.configs = map->data.configs.configs;return 0;
}

现在都仅仅是分析了pinmux_map_to_setting和pinconf_map_to_setting，具体它们的作用我们在后面才能看的出来，所以继续分析吧！到这里pinctrl_get分析完了，执行完pinctrl_get，就意味着该设备的所有和pin相关的设备树信息已经解析完成，并生成了用于管理、配置的数据结构，为以后的其他api提供了支持。其他驱动一般不会直接调用pinctrl_get，而是调用它的变体devm_pinctrl_get或者pinctrl_get_select来初始化设备。devm_pinctrl_get就不用说了啦，pinctrl_get_select类似与pinctrl_register调用pinctrl_get及它后的那段代码的结合，不仅调用了pinctrl_get，还根据输入参数让设备处于指定的状态。通过pinctrl_select_state来让设备处于指定的状态，下面开始分析它，通过分析它，应该就清楚了前面各种填充的作用啦！

int pinctrl_select_state(struct pinctrl *p, struct pinctrl_state *state)  
{struct pinctrl_setting *setting, *setting2;struct pinctrl_state *old_state = p->state;int ret;//如果当前就是该状态，直接返回成功if (p->state == state)return 0;//如果之前有设置过状态，那需要做一些额外处理if (p->state) {/** The set of groups with a mux configuration in the old state* may not be identical to the set of groups with a mux setting* in the new state. While this might be unusual, it's entirely* possible for the "user"-supplied mapping table to be written* that way. For each group that was configured in the old state* but not in the new state, this code puts that group into a* safe/disabled state.*/list_for_each_entry(setting, &p->state->settings, node) {bool found = false;if (setting->type != PIN_MAP_TYPE_MUX_GROUP)continue;list_for_each_entry(setting2, &state->settings, node) {if (setting2->type != PIN_MAP_TYPE_MUX_GROUP)continue;if (setting2->data.mux.group ==setting->data.mux.group) {found = true;break;}}if (!found)pinmux_disable_setting(setting);}}p->state = NULL;/* Apply all the settings for the new state *///list_for_each_entry(setting, &state->settings, node) {//遍历该设备的该状态下的所有设置，一个个设置上去switch (setting->type) {case PIN_MAP_TYPE_MUX_GROUP://如果该设置是mux设置，那么调用pinmux_enable_setting，这里面//就用到了前面填充的信息ret = pinmux_enable_setting(setting);break;case PIN_MAP_TYPE_CONFIGS_PIN:case PIN_MAP_TYPE_CONFIGS_GROUP://如果该设置是conf设置，那么调用pinconf_apply_setting，//这里面就用到了前面填充的信息ret = pinconf_apply_setting(setting);break;default:ret = -EINVAL;break;}if (ret < 0) {goto unapply_new_state;}}p->state = state;return 0;unapply_new_state:  dev_err(p->dev, "Error applying setting, reverse things back\n");list_for_each_entry(setting2, &state->settings, node) {if (&setting2->node == &setting->node)break;/** All we can do here is pinmux_disable_setting.* That means that some pins are muxed differently now* than they were before applying the setting (We can't* "unmux a pin"!), but it's not a big deal since the pins* are free to be muxed by another apply_setting.*/if (setting2->type == PIN_MAP_TYPE_MUX_GROUP)pinmux_disable_setting(setting2);}/* There's no infinite recursive loop here because p->state is NULL */if (old_state)pinctrl_select_state(p, old_state);return ret;
}