gpio子系统和pinctrl子系统（三）

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

情景分析

打算从两个角度来情景分析，先从bsp驱动工程师的角度，然后是驱动工程师的角度，下面以三星s3c6410　Pinctrl-samsung.c为例看看pinctrl输入参数的初始化过程（最开始的zynq平台的pin配置貌似是通过bitstreams来的，内核层没看到有关配置pin的代码，不过最新的zynq代码里加入了pinctrl，但我手上的恰好的较早其的zynq代码，所以这里以三星的代码为例子），不过这里贴的代码有点多（尽量将无关的代码删掉），耐心的看吧^_^

bsp驱动工程师的角度

static int samsung_pinctrl_probe(struct platform_device *pdev)  
{
    ...
    ...
    ...
    //解析pinctrl信息，后面分析
    ctrl = samsung_pinctrl_get_soc_data(drvdata, pdev);
    drvdata->ctrl = ctrl;
    drvdata->dev = dev;

    ...
    ...
    ...
    //向gpio子系统注册（三星有用gpio子系统）
    ret = samsung_gpiolib_register(pdev, drvdata);
    if (ret)
        return ret;

    //向pinctrl子系统注册
    ret = samsung_pinctrl_register(pdev, drvdata);
    if (ret) {
        samsung_gpiolib_unregister(pdev, drvdata);
        return ret;
    }

    ...
    ...
    ...

    return 0;
}

先贴下6410 pinctrl设备树信息(arch/arm/boot/dts/s3c64xx.dtsi)：

aliases {  
    i2c0 = &i2c0;                                                           
    pinctrl0 = &pinctrl0;                                                   
}; 

pinctrl0: pinctrl@7f008000 {  
    compatible = "samsung,s3c64xx-pinctrl";                             
    reg = <0x7f008000 0x1000>;                                          
    interrupt-parent = <&vic1>;                                         
    interrupts = <21>;                                                  

    pctrl_int_map: pinctrl-interrupt-map {                              
        interrupt-map = <0 &vic0 0>,                                    
                <1 &vic0 1>,                                            
                <2 &vic1 0>,                                            
                <3 &vic1 1>;                                            
        #address-cells = <0>;                                           
        #size-cells = <0>;                                              
        #interrupt-cells = <1>;                                         
    };                                                                  

    wakeup-interrupt-controller {                                       
        compatible = "samsung,s3c64xx-wakeup-eint";                     
        interrupts = <0>, <1>, <2>, <3>;                                
        interrupt-parent = <&pctrl_int_map>;                            
    };                                                                  
};  

下面边看代码边对照上面的设备树描述，看看解析过程:

static struct samsung_pin_ctrl *samsung_pinctrl_get_soc_data(  
                struct samsung_pinctrl_drv_data *d,
                struct platform_device *pdev)
{
    int id;
    const struct of_device_id *match;
    struct device_node *node = pdev->dev.of_node;
    struct device_node *np;
    struct samsung_pin_ctrl *ctrl;
    struct samsung_pin_bank *bank;
    int i;

    //获取pinctrl的alias id，其实就是上面的pinctrl0了
    id = of_alias_get_id(node, "pinctrl");
    if (id < 0) {
        dev_err(&pdev->dev, "failed to get alias id\n");
        return NULL;
    }
    //获取该节点对应的match
    match = of_match_node(samsung_pinctrl_dt_match, node);
    //通过id找到对应的pinctrl，因为三星的有些soc是存在多个pinctrl的，
    //也就是说pinctrl0，pinctrl1等等同时存在，这里就是获取第id个，对于6410，就一个
    //struct samsung_pin_ctrl s3c64xx_pin_ctrl[] = {
    //    {
    //        /* pin-controller instance 1 data */
    //        .pin_banks    = s3c64xx_pin_banks0,
    //        .nr_banks    = ARRAY_SIZE(s3c64xx_pin_banks0),
    //        .eint_gpio_init = s3c64xx_eint_gpio_init,
    //        .eint_wkup_init = s3c64xx_eint_eint0_init,
    //        .label        = "S3C64xx-GPIO",
    //    },
    //};
    对于exynos5420，就存在多个啦：
    //struct samsung_pin_ctrl exynos5420_pin_ctrl[] = {
    //    {
    //        /* pin-controller instance 0 data */
    //        .pin_banks    = exynos5420_pin_banks0,
    //        .nr_banks    = ARRAY_SIZE(exynos5420_pin_banks0),
    //        .geint_con    = EXYNOS_GPIO_ECON_OFFSET,
    //        .geint_mask    = EXYNOS_GPIO_EMASK_OFFSET,
    //        .geint_pend    = EXYNOS_GPIO_EPEND_OFFSET,
    //        .weint_con    = EXYNOS_WKUP_ECON_OFFSET,
    //        .weint_mask    = EXYNOS_WKUP_EMASK_OFFSET,
    //        .weint_pend    = EXYNOS_WKUP_EPEND_OFFSET,
    //        .svc        = EXYNOS_SVC_OFFSET,
    //        .eint_gpio_init = exynos_eint_gpio_init,
    //        .eint_wkup_init = exynos_eint_wkup_init,
    //        .label        = "exynos5420-gpio-ctrl0",
    //    }, {
    //        /* pin-controller instance 1 data */
    //        .pin_banks    = exynos5420_pin_banks1,
    //        .nr_banks    = ARRAY_SIZE(exynos5420_pin_banks1),
    //        .geint_con    = EXYNOS_GPIO_ECON_OFFSET,
    //       .geint_mask    = EXYNOS_GPIO_EMASK_OFFSET,
    //        .geint_pend    = EXYNOS_GPIO_EPEND_OFFSET,
    //        .svc        = EXYNOS_SVC_OFFSET,
    //        .eint_gpio_init = exynos_eint_gpio_init,
    //        .label        = "exynos5420-gpio-ctrl1",
    //    },
    //    ...
    //    ...
    //    ...
    //};
    ctrl = (struct samsung_pin_ctrl *)match->data + id;
    //提取pin ctrl里的banks信息，这里就是ARRAY_SIZE(s3c64xx_pin_banks0)
    bank = ctrl->pin_banks;
    //遍历每一个bank，填充相应的信息
    for (i = 0; i < ctrl->nr_banks; ++i, ++bank) {
        spin_lock_init(&bank->slock);
        bank->drvdata = d;
        //设置bank的pin　base
        bank->pin_base = ctrl->nr_pins;
        //更新ctrl->nr_pins，即该pin ctrl的pin数量，在后面的注册时会用到该成员
        ctrl->nr_pins += bank->nr_pins;
    }

    //遍历该节点的每一个子节点，上面的s3c64xx.dtsi文件末尾有一个
    //#include "s3c64xx-pinctrl.dtsi" 语句，s3c64xx-pinctrl.dtsi里
    //的信息是对当前节点pinctrl0的补充，内容如下：
    //&pinctrl0 {                                                                     
    ///*                                                                          
    // * Pin banks                                                                
    // */                                                                         
    //
    //gpa: gpa {                                                                  
    //    gpio-controller;                                                        
    //    #gpio-cells = <2>;                                                      
    //    interrupt-controller;                                                   
    //    #interrupt-cells = <2>;                                                 
    //};                                                                          
    //
    //gpb: gpb {                                                                  
    //    gpio-controller;                                                        
    //    #gpio-cells = <2>;                                                      
    //    interrupt-controller;                                                   
    //    #interrupt-cells = <2>;                                                 
    //};                                                                          

    //gpc: gpc {                                                                  
    //    gpio-controller;                                                        
    //    #gpio-cells = <2>;                                                      
    //    interrupt-controller;                                                   
    //    #interrupt-cells = <2>;                                                 
    //};          
    //...
    //...
    //...
    //hsi_bus: hsi-bus {                                                          
    //    samsung,pins = "gpk-0", "gpk-1", "gpk-2", "gpk-3",                      
    //            "gpk-4", "gpk-5", "gpk-6", "gpk-7";                             
    //    samsung,pin-function = <3>;                                             
    //    samsung,pin-pud = ;                                      
    //};     
    //}
    //这里就是处理这些子节点
    for_each_child_of_node(node, np) {
        //如果该子节点没有gpio-controller属性，跳过处理，这里处理的是bank
        //只和gpio有关，所以跳过不关心的
        if (!of_find_property(np, "gpio-controller", NULL))
            continue;
        bank = ctrl->pin_banks;
        for (i = 0; i < ctrl->nr_banks; ++i, ++bank) {
            if (!strcmp(bank->name, np->name)) {
                //将bank对应到它自己的设备节点
                bank->of_node = np;
                break;
            }
        }
    }

    ctrl->base = pin_base;
    pin_base += ctrl->nr_pins;

    return ctrl;
}

填充完必要的信息，就开始注册了，先看pinctrl的注册吧！注意，传入的参数drvdata是已经经过前面的解析填入了很多信息的

static int samsung_pinctrl_register(struct platform_device *pdev,  
                    struct samsung_pinctrl_drv_data *drvdata)
{
    struct pinctrl_desc *ctrldesc = &drvdata->pctl;
    struct pinctrl_pin_desc *pindesc, *pdesc;
    struct samsung_pin_bank *pin_bank;
    char *pin_names;
    int pin, bank, ret;

    //初始化pinctrl_desc，register的时候要用
    ctrldesc->name = "samsung-pinctrl";
    ctrldesc->owner = THIS_MODULE;
    //这个ops是必须要的，里面的几个函数前面也都用到了，主要有
    //get_groups_count、dt_node_to_map、get_group_pins
    ctrldesc->pctlops = &samsung_pctrl_ops;
    //这个是pinctrl chip driver根据自己平台的特性，可选的支持的
    //主要有request、get_functions_count、get_function_groups、
    //enable，和gpio相关的还有额外几个gpio_request_enable、gpio_disable_free、gpio_set_direction
    ctrldesc->pmxops = &samsung_pinmux_ops;
    //这个是pinctrl chip driver根据自己平台的特性，可选的支持的
    //主要有pin_config_get、pin_config_set、pin_config_group_get、pin_config_group_set
    ctrldesc->confops = &samsung_pinconf_ops;

    //下面这部分也是pinctrl chip driver根据自己平台的特性必须填充的，用于表示该pinctrl chip
    //所有的pin信息
    pindesc = devm_kzalloc(&pdev->dev, sizeof(*pindesc) *
            drvdata->ctrl->nr_pins, GFP_KERNEL);
    if (!pindesc) {
        dev_err(&pdev->dev, "mem alloc for pin descriptors failed\n");
        return -ENOMEM;
    }
    ctrldesc->pins = pindesc;
    ctrldesc->npins = drvdata->ctrl->nr_pins;//该成员就是samsung_pin_ctrl填充的

    //填充pin号
    /* dynamically populate the pin number and pin name for pindesc */
    for (pin = 0, pdesc = pindesc; pin < ctrldesc->npins; pin++, pdesc++)
        pdesc->number = pin + drvdata->ctrl->base;//该成员也是由samsung_pin_ctrl填充的

    //分配空间，用于填充pin名字
    /*
     * allocate space for storing the dynamically generated names for all
     * the pins which belong to this pin-controller.
     */
    pin_names = devm_kzalloc(&pdev->dev, sizeof(char) * PIN_NAME_LENGTH *
                    drvdata->ctrl->nr_pins, GFP_KERNEL);
    if (!pin_names) {
        dev_err(&pdev->dev, "mem alloc for pin names failed\n");
        return -ENOMEM;
    }

    /* for each pin, the name of the pin is pin-bank name + pin number */
    for (bank = 0; bank < drvdata->ctrl->nr_banks; bank++) {
        pin_bank = &drvdata->ctrl->pin_banks[bank];
        for (pin = 0; pin < pin_bank->nr_pins; pin++) {
            //填充pin的名字，注意这里的格式，设备树里的命名就得按照该格式，即bank名字+pin号
            sprintf(pin_names, "%s-%d", pin_bank->name, pin);
            pdesc = pindesc + pin_bank->pin_base + pin;
            pdesc->name = pin_names;
            pin_names += PIN_NAME_LENGTH;
        }
    }

    //到现在，离注册需要的条件就剩function和group的填充了，其实它们不是pinctrl子系统要求的，
    //但是回调函数的实现依赖这些，因此需要解析设备树信息来填充它们，后面会详细分析该函数
    ret = samsung_pinctrl_parse_dt(pdev, drvdata);
    if (ret)
        return ret;

    //一切准备好后，就注册了
    drvdata->pctl_dev = pinctrl_register(ctrldesc, &pdev->dev, drvdata);
    if (!drvdata->pctl_dev) {
        dev_err(&pdev->dev, "could not register pinctrl driver\n");
        return -EINVAL;
    }

    //
    for (bank = 0; bank < drvdata->ctrl->nr_banks; ++bank) {
        pin_bank = &drvdata->ctrl->pin_banks[bank];
        pin_bank->grange.name = pin_bank->name;
        pin_bank->grange.id = bank;
        pin_bank->grange.pin_base = pin_bank->pin_base;
        pin_bank->grange.base = pin_bank->gpio_chip.base;
        pin_bank->grange.npins = pin_bank->gpio_chip.ngpio;
        pin_bank->grange.gc = &pin_bank->gpio_chip;
        pinctrl_add_gpio_range(drvdata->pctl_dev, &pin_bank->grange);
    }

    return 0;
}

samsung_pinctrl_parse_dt分析：

static int samsung_pinctrl_parse_dt(struct platform_device *pdev,  
                    struct samsung_pinctrl_drv_data *drvdata)
{
    ...
    //获取pinctrl设备的子节点数量，前面已经讲过有哪些子节点了，不再重复
    grp_cnt = of_get_child_count(dev_np);
    if (!grp_cnt)
        return -EINVAL;

    //根据获取的数量，分配空间，每个配置节点对应于一个group（pin的集合）
    groups = devm_kzalloc(dev, grp_cnt * sizeof(*groups), GFP_KERNEL);
    if (!groups) {
        dev_err(dev, "failed allocate memory for ping group list\n");
        return -EINVAL;
    }
    grp = groups;

    //根据获取的数量，分配空间，每个配置节点对应的功能
    functions = devm_kzalloc(dev, grp_cnt * sizeof(*functions), GFP_KERNEL);
    if (!functions) {
        dev_err(dev, "failed to allocate memory for function list\n");
        return -EINVAL;
    }
    func = functions;

    //遍历每一个子节点，一个个处理
    /*
     * Iterate over all the child nodes of the pin controller node
     * and create pin groups and pin function lists.
     */
    for_each_child_of_node(dev_np, cfg_np) {
        u32 function;
        //检查samsung,pins属性
        if (!of_find_property(cfg_np, "samsung,pins", NULL))
            continue;

        //将samsung,pins属性里面指定的名字列表转换为pin号列表
        //，这里面会用到前面samsung_pinctrl_get_soc_data填充的信息来匹配
        ret = samsung_pinctrl_parse_dt_pins(pdev, cfg_np,
                    &drvdata->pctl, &pin_list, &npins);
        if (ret)
            return ret;

        //下面就是构成一个pin group了，注意pin组的名字
        //，是配置节点名+GROUP_SUFFIX，GROUP_SUFFIX为-grp
        /* derive pin group name from the node name */
        gname = devm_kzalloc(dev, strlen(cfg_np->name) + GSUFFIX_LEN,
                    GFP_KERNEL);
        if (!gname) {
            dev_err(dev, "failed to alloc memory for group name\n");
            return -ENOMEM;
        }
        sprintf(gname, "%s%s", cfg_np->name, GROUP_SUFFIX);

        grp->name = gname;
        grp->pins = pin_list;
        grp->num_pins = npins;
        of_property_read_u32(cfg_np, "samsung,pin-function", &function);
        grp->func = function;
        grp++;

        if (!of_find_property(cfg_np, "samsung,pin-function", NULL))
            continue;

        //如果存在samsung,pin-function属性，那么构建一个功能名
        //，功能名组合方式是配置节点名+FUNCTION_SUFFIX，FUNCTION_SUFFIX为-mux
        /* derive function name from the node name */
        fname = devm_kzalloc(dev, strlen(cfg_np->name) + FSUFFIX_LEN,
                    GFP_KERNEL);
        if (!fname) {
            dev_err(dev, "failed to alloc memory for func name\n");
            return -ENOMEM;
        }
        sprintf(fname, "%s%s", cfg_np->name, FUNCTION_SUFFIX);

        func->name = fname;
        func->groups = devm_kzalloc(dev, sizeof(char *), GFP_KERNEL);
        if (!func->groups) {
            dev_err(dev, "failed to alloc memory for group list "
                    "in pin function");
            return -ENOMEM;
        }
        func->groups[0] = gname;
        func->num_groups = 1;
        func++;
        func_idx++;
    }

    //存储下解析的数据信息
    drvdata->pin_groups = groups;
    drvdata->nr_groups = grp_cnt;
    drvdata->pmx_functions = functions;
    drvdata->nr_functions = func_idx;

    return 0;
}

下面通过分析各个ops，来进一步理解下上面几个函数所起的作用：

static const struct pinctrl_ops samsung_pctrl_ops = {  
    .get_groups_count   = samsung_get_group_count,
    .get_group_name     = samsung_get_group_name,
    .get_group_pins     = samsung_get_group_pins,
    .dt_node_to_map     = samsung_dt_node_to_map,
    .dt_free_map        = samsung_dt_free_map,
};
static const struct pinmux_ops samsung_pinmux_ops = {  
    .get_functions_count    = samsung_get_functions_count,
    .get_function_name  = samsung_pinmux_get_fname,
    .get_function_groups    = samsung_pinmux_get_groups,
    .enable         = samsung_pinmux_enable,
    .disable        = samsung_pinmux_disable,
    //由pinmux_gpio_direction间接调用，最开始应该是gpio子系统
    //的gpio_pin_direction_input、gpio_pin_direction_output触发
    .gpio_set_direction = samsung_pinmux_gpio_set_direction,
};
static const struct pinconf_ops samsung_pinconf_ops = {  
    .pin_config_get     = samsung_pinconf_get,
    .pin_config_set     = samsung_pinconf_set,
    .pin_config_group_get   = samsung_pinconf_group_get,
    .pin_config_group_set   = samsung_pinconf_group_set,
};

从上面一路分析下路来，我们应该知道dt_node_to_map是最先调用的，其次是get_functions_count、get_function_name、get_function_groups、get_groups_count、get_group_name、get_group_pins、request（三星pinmux_ops没有实现它）、enable、pin_config_set、pin_config_group_set所以我打算就按这个顺序进行分析。

调用dt_node_to_map的时候，从前文应该很清楚了吧，就是在某一个设备（pinctrl本身也算是一个设备，不过从前文贴出来的pinctrl0里，我没发现有pinctrl-xxx的属性，也就是说不需要对它做任何pin　ctrl）用pinctrl_get请求解析自己设备树信息的时候，说的更准确点的话，就是解析该设备里某一个状态的某一个配置（一个状态可能需要多个配置来完成）的时候。下面用某一个子设备的设备树信息为例子，对应文件s3c6410-smdk6410.dts

#define PIN_PULL_NONE   0  

&uart0 {                                                                        
    pinctrl-names = "default";                                                  
    pinctrl-0 = <&uart0_data>, <&uart0_fctl>;                                   
    status = "okay";                                                            
};
uart0_data: uart0-data {  
    samsung,pins = "gpa-0", "gpa-1";                                        
    samsung,pin-function = <2>;                                             
    samsung,pin-pud = ;                                      
};       
uart0_fctl: uart0-fctl {  
    samsung,pins = "gpa-2", "gpa-3";                                        
    samsung,pin-function = <2>;                                             
    samsung,pin-pud = ;                                      
};

//下面部分是uart0的其他信息，和本文关心的pinctrl无关，之所以也列出来，只是不想让读者对这部分有误解
uart0: serial@7f005000 {  
    compatible = "samsung,s3c6400-uart";                                
    reg = <0x7f005000 0x100>;                                           
    interrupt-parent = <&vic1>;                                         
    interrupts = <5>;                                                   
    clock-names = "uart", "clk_uart_baud2",                             
            "clk_uart_baud3";                                           
    clocks = <&clocks PCLK_UART0>, <&clocks PCLK_UART0>,                
            <&clocks SCLK_UART>;                                        
    status = "disabled";                                                
};  

对应的解析代码如下，从前文描述应该清楚，期望回调函数返回该设备该状态该配置下的所有设置信息（可能只存在mux设置，也可能同时存在mux和conf设置），而上面的设备树里的uart0只有一个状态，default，对应的配置有两个，一个是uart0_data，一个是uart0_fctl，它们都是对配置节点的引用，配置节点都是pinctrl节点下的子节点，下面看代码吧：

static int samsung_dt_node_to_map(struct pinctrl_dev *pctldev,  
            struct device_node *np, struct pinctrl_map **maps,
            unsigned *nmaps)
{
...
    //检查该节点（第一次调用应该是uart0_data节点，第二次调用应该是uart0_fctl节点啦）
    //含有多少个自己定义的属性，包括：
    //{ "samsung,pin-pud", PINCFG_TYPE_PUD },
    //{ "samsung,pin-drv", PINCFG_TYPE_DRV },
    //{ "samsung,pin-con-pdn", PINCFG_TYPE_CON_PDN },
    //{ "samsung,pin-pud-pdn", PINCFG_TYPE_PUD_PDN },    
    /* count the number of config options specfied in the node */
    for (idx = 0; idx < ARRAY_SIZE(pcfgs); idx++) {
        if (of_find_property(np, pcfgs[idx].prop_cfg, NULL))
            cfg_cnt++;
    }

    /*
     * Find out the number of map entries to create. All the config options
     * can be accomadated into a single config map entry.
     */
    //如果有，那么说明需要继续后面的conf操作
    if (cfg_cnt)
        map_cnt = 1;
    //如果存在samsung,pin-function属性，那么不仅要做后面的操作，还需要额外做一些mux操作
    if (of_find_property(np, "samsung,pin-function", NULL))
        map_cnt++;
    if (!map_cnt) {
        dev_err(dev, "node %s does not have either config or function "
                "configurations\n", np->name);
        return -EINVAL;
    }

    //分配空间
    /* Allocate memory for pin-map entries */
    map = kzalloc(sizeof(*map) * map_cnt, GFP_KERNEL);
    if (!map) {
        dev_err(dev, "could not alloc memory for pin-maps\n");
        return -ENOMEM;
    }
    *nmaps = 0;

    //从前面的分析应该清楚了组名的格式，下面就是根据配置节点名构建一个格式，然后到系统
    //里找对应的信息
    /*
     * Allocate memory for pin group name. The pin group name is derived
     * from the node name from which these map entries are be created.
     */
    gname = kzalloc(strlen(np->name) + GSUFFIX_LEN, GFP_KERNEL);
    if (!gname) {
        dev_err(dev, "failed to alloc memory for group name\n");
        goto free_map;
    }
    sprintf(gname, "%s%s", np->name, GROUP_SUFFIX);

    /*
     * don't have config options? then skip over to creating function
     * map entries.
     */
    if (!cfg_cnt)
        goto skip_cfgs;

    //根据前面获取的数量来分配配置节点空间
    /* Allocate memory for config entries */
    cfg = kzalloc(sizeof(*cfg) * cfg_cnt, GFP_KERNEL);
    if (!cfg) {
        dev_err(dev, "failed to alloc memory for configs\n");
        goto free_gname;
    }

    //将已经定义的，属于自己定义列表里面的属性值提取出来，对应于我们这里，都是PIN_PULL_NONE
    /* Prepare a list of config settings */
    for (idx = 0, cfg_cnt = 0; idx < ARRAY_SIZE(pcfgs); idx++) {
        u32 value;
        if (!of_property_read_u32(np, pcfgs[idx].prop_cfg, &value))
            cfg[cfg_cnt++] =
                PINCFG_PACK(pcfgs[idx].cfg_type, value);
    }

    //创建设置信息，如设置名字，类型，以及多少个conf操作，每一个conf值
    /* create the config map entry */
    map[*nmaps].data.configs.group_or_pin = gname;
    map[*nmaps].data.configs.configs = cfg;
    map[*nmaps].data.configs.num_configs = cfg_cnt;
    map[*nmaps].type = PIN_MAP_TYPE_CONFIGS_GROUP;
    *nmaps += 1;

skip_cfgs:  
    /* create the function map entry */
    if (of_find_property(np, "samsung,pin-function", NULL)) {
        //如果存在samsung,pin-function属性，说明有mux的需求，处理它
        //这里是构建功能名，和前面初始化的时候一致
        fname = kzalloc(strlen(np->name) + FSUFFIX_LEN, GFP_KERNEL);
        if (!fname) {
            dev_err(dev, "failed to alloc memory for func name\n");
            goto free_cfg;
        }
        sprintf(fname, "%s%s", np->name, FUNCTION_SUFFIX);

        //填充mux操作需要的信息，如哪一个设备，哪一个功能
        map[*nmaps].data.mux.group = gname;
        map[*nmaps].data.mux.function = fname;
        map[*nmaps].type = PIN_MAP_TYPE_MUX_GROUP;
        *nmaps += 1;
    }

    *maps = map;
    return 0;
...
}

samsung_get_functions_count，它用于获取功能的总数量drvdata->nr_functions，前面已经分析过初始化这个的过程，所以这里就不再分析。samsung_pinmux_get_fname从已经初始化的数据结构里拿出对应索引上的name，name就是由配置节点名＋-mux后缀构成。pinctrl_get的过程（pinmux_map_to_setting），会以map->data.mux.function为参数调用samsung_pinmux_get_fname获取该功能对应的索引来初始化setting->data.mux.func，然后在用samsung_pinmux_get_groups获取的组信息里，用前面解析出来的map[*nmaps].data.mux.group作为输入参数，获取该组的索引来初始化setting->data.mux.group。最后在pinctrl_select_state的时候，会通过上面的信息并结合最开始初始化的一些数据结构进行mux和conf操作。pinconf_map_to_setting的操作类似，不再重复。在pinctrl_select_state的时候samsung_pinmux_enable和samsung_pinconf_set有可能会触发，这里就不再继续分析了，但还是贴出代码吧！

/* enable a specified pinmux by writing to registers */
static int samsung_pinmux_enable(struct pinctrl_dev *pctldev, unsigned selector,  
                    unsigned group)
{
    samsung_pinmux_setup(pctldev, selector, group, true);
    return 0;
}

static void samsung_pinmux_setup(struct pinctrl_dev *pctldev, unsigned selector,  
                    unsigned group, bool enable)
{
    struct samsung_pinctrl_drv_data *drvdata;
    const unsigned int *pins;
    struct samsung_pin_bank *bank;
    void __iomem *reg;
    u32 mask, shift, data, pin_offset, cnt;
    unsigned long flags;

    drvdata = pinctrl_dev_get_drvdata(pctldev);
    pins = drvdata->pin_groups[group].pins;

    /*
     * for each pin in the pin group selected, program the correspoding pin
     * pin function number in the config register.
     */
    for (cnt = 0; cnt < drvdata->pin_groups[group].num_pins; cnt++) {
        struct samsung_pin_bank_type *type;

        pin_to_reg_bank(drvdata, pins[cnt] - drvdata->ctrl->base,
                ®, &pin_offset, &bank);
        type = bank->type;
        mask = (1 << type->fld_width[PINCFG_TYPE_FUNC]) - 1;
        shift = pin_offset * type->fld_width[PINCFG_TYPE_FUNC];
        if (shift >= 32) {
            /* Some banks have two config registers */
            shift -= 32;
            reg += 4;
        }

        spin_lock_irqsave(&bank->slock, flags);

        data = readl(reg + type->reg_offset[PINCFG_TYPE_FUNC]);
        data &= ~(mask << shift);
        if (enable)
            data |= drvdata->pin_groups[group].func << shift;
        writel(data, reg + type->reg_offset[PINCFG_TYPE_FUNC]);

        spin_unlock_irqrestore(&bank->slock, flags);
    }
}

/* set the pin config settings for a specified pin */
static int samsung_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin,  
                unsigned long *configs, unsigned num_configs)
{
    int i, ret;

    for (i = 0; i < num_configs; i++) {
        ret = samsung_pinconf_rw(pctldev, pin, &configs[i], true);
        if (ret < 0)
            return ret;
    } /* for each config */

    return 0;
}

/* set or get the pin config settings for a specified pin */
static int samsung_pinconf_rw(struct pinctrl_dev *pctldev, unsigned int pin,  
                unsigned long *config, bool set)
{
    struct samsung_pinctrl_drv_data *drvdata;
    struct samsung_pin_bank_type *type;
    struct samsung_pin_bank *bank;
    void __iomem *reg_base;
    enum pincfg_type cfg_type = PINCFG_UNPACK_TYPE(*config);
    u32 data, width, pin_offset, mask, shift;
    u32 cfg_value, cfg_reg;
    unsigned long flags;

    drvdata = pinctrl_dev_get_drvdata(pctldev);
    pin_to_reg_bank(drvdata, pin - drvdata->ctrl->base, ®_base,
                    &pin_offset, &bank);
    type = bank->type;

    if (cfg_type >= PINCFG_TYPE_NUM || !type->fld_width[cfg_type])
        return -EINVAL;

    width = type->fld_width[cfg_type];
    cfg_reg = type->reg_offset[cfg_type];

    spin_lock_irqsave(&bank->slock, flags);

    mask = (1 << width) - 1;
    shift = pin_offset * width;
    data = readl(reg_base + cfg_reg);

    if (set) {
        cfg_value = PINCFG_UNPACK_VALUE(*config);
        data &= ~(mask << shift);
        data |= (cfg_value << shift);
        writel(data, reg_base + cfg_reg);
    } else {
        data >>= shift;
        data &= mask;
        *config = PINCFG_PACK(cfg_type, data);
    }

    spin_unlock_irqrestore(&bank->slock, flags);

    return 0;
}

/* set the pin config settings for a specified pin group */
static int samsung_pinconf_group_set(struct pinctrl_dev *pctldev,  
            unsigned group, unsigned long *configs,
            unsigned num_configs)
{
    struct samsung_pinctrl_drv_data *drvdata;
    const unsigned int *pins;
    unsigned int cnt;

    drvdata = pinctrl_dev_get_drvdata(pctldev);
    pins = drvdata->pin_groups[group].pins;

    for (cnt = 0; cnt < drvdata->pin_groups[group].num_pins; cnt++)
        samsung_pinconf_set(pctldev, pins[cnt], configs, num_configs);

    return 0;
}

驱动工程师的角度

一般会用到的接口： 
devm_pinctrl_get 
pinctrl_lookup_state 
pinctrl_select_state

操作gpio时，会用到的接口： 
pinctrl_request_gpio 
pinctrl_gpio_direction_input 
pinctrl_gpio_direction_output

还有一些额外变体，懒得贴了

下面以gpio方式的api为例子继续分析，这样也好与文章最开始的gpio子系统结合起来理解！pinctrl_request_gpio在驱动里，主要有两类会用到它，一类是gpio子系统的实现者，即gpio-xxx.c那些文件，另一类是pinctrl的实现者，即pinctrl-xxx.c那些文件。它们在注册gpio chip时，将pinctrl_request_gpio作为gpio chip里request，这样间接将pinctrl操作交给gpio子系统自动完成。从gpio子系统分析可知，request的调用是在gpio_request或者gpiod_get间接触发。看一下pinctrl_request_gpio做了些什么：

int pinctrl_request_gpio(unsigned gpio)  
{
    struct pinctrl_dev *pctldev;
    struct pinctrl_gpio_range *range;
    int ret;
    int pin;
    //这里会通过gpio来取得该gpio对应的pctldev和range，还记得分析gpiochip_add时的
    //of_gpiochip_add_pin_range吧，这里就用到了它add的信息
    ret = pinctrl_get_device_gpio_range(gpio, &pctldev, &range);
    if (ret) {
        if (pinctrl_ready_for_gpio_range(gpio))
            ret = 0;
        return ret;
    }

    mutex_lock(&pctldev->mutex);

    /* Convert to the pin controllers number space */
    //有了range就好办了啦，它里面有gpio与pin号的对应关系，当然这关系是最开始从设备树里解析过来的
    pin = gpio_to_pin(range, gpio);

    //有了所有信息调用pinmux_request_gpio进一步request吧
    ret = pinmux_request_gpio(pctldev, range, pin, gpio);

    mutex_unlock(&pctldev->mutex);

    return ret;
}

继续pinmux_request_gpio：

int pinmux_request_gpio(struct pinctrl_dev *pctldev,  
            struct pinctrl_gpio_range *range,
            unsigned pin, unsigned gpio)
{
    const char *owner;
    int ret;

    /* Conjure some name stating what chip and pin this is taken by */
    owner = kasprintf(GFP_KERNEL, "%s:%d", range->name, gpio);
    if (!owner)
        return -EINVAL;
    //pin_request之前分析的时候有看到调用过，不过这次gpio的时候会传入range，导致它的
    //调用流程会有所不同，里面会触发pinmux_ops的gpio_request_enable回调，而不是request回调
    ret = pin_request(pctldev, pin, owner, range);
    if (ret < 0)
        kfree(owner);

    return ret;
}

最后看看设备驱动模型中pinctrl的影子，在bus_probe_device的时候，会调用device_attach，而device_attach里会调用__device_attach去attach，在匹配成功后，会调用driver_probe_device，它会导致really_probe的调用来进行驱动的probe，最终会导致pinctrl_bind_pins调用，这个函数会pinctrl_get并设置设备的初始状态，这个过程不需要驱动额外做任何事情，多么巧妙啊　

int pinctrl_bind_pins(struct device *dev)  
{
    int ret;

    dev->pins = devm_kzalloc(dev, sizeof(*(dev->pins)), GFP_KERNEL);
    if (!dev->pins)
        return -ENOMEM;

    dev->pins->p = devm_pinctrl_get(dev);
    if (IS_ERR(dev->pins->p)) {
        dev_dbg(dev, "no pinctrl handle\n");
        ret = PTR_ERR(dev->pins->p);
        goto cleanup_alloc;
    }

    dev->pins->default_state = pinctrl_lookup_state(dev->pins->p,
                    PINCTRL_STATE_DEFAULT);
    if (IS_ERR(dev->pins->default_state)) {
        dev_dbg(dev, "no default pinctrl state\n");
        ret = 0;
        goto cleanup_get;
    }

    ret = pinctrl_select_state(dev->pins->p, dev->pins->default_state);
    if (ret) {
        dev_dbg(dev, "failed to activate default pinctrl state\n");
        goto cleanup_get;
    }
...
}

总结

通过对gpio子系统和pinctrl子系统的分析，应该对这两个系统有了大致的概念了吧^_^　gpio子系统让驱动工程师不用关心底层gpio chip的具体实现，让bsp工程师不用关心上层驱动工程师的使用方式。pinctrl子系统帮我们管理了pin信息，包括了pin的mux和conf，同时也透明的处理了与gpio子系统的关联以及设备模型的关联。