解析linux或android添加文件系统的属性接口的方法

第一种：

1、添加关键头文件：

#include <linux/of_gpio.h>#include <linux/gpio.h>#include <linux/delay.h>#include <linux/module.h>#include <linux/types.h>#include <linux/kobject.h>

2、在已经存在驱动文件中搜索'DEVICE_ATTR'关键字，如果存在，直接参考已经存在的方法添加一个即可，如下：

unsigned int Gpio134_OtgID = 134; //定义全局变量static unsigned int otgid_status = 1;…

3、定义文件系统的读写函数：

//add zhaojr gpio134 control OTG ID for host or device mode static ssize_t setotgid_store(struct device *dev, struct device_attribute *attr,const char *buf, size_t count) { unsigned int ret=0; pr_err('%s: n', __func__); //ret = kstrtoint(buf, 10, &otgid_status); ret = kstrtouint(buf, 10, &otgid_status); //sscanf(buf, '%lu', &otgid_status); if (ret < 0){ pr_err('%s::kstrtouint() failed n', __func__); } //sscanf(buf, '%d', &otgid_status); pr_err('%s: otgid_status=%d n', __func__,otgid_status); if(otgid_status > 0){ gpio_set_value(Gpio134_OtgID, 1); }else{ gpio_set_value(Gpio134_OtgID, 0); } return count;}static ssize_t setotgid_show(struct device *dev,struct device_attribute *attr, char *buf) { pr_err('%s: n', __func__); return sprintf(buf, '%dn',otgid_status);}//static DEVICE_ATTR_RW(setotgid);/*struct device_attribute dev_attr_setotgid = { .attr = {.name ='setotgid', .mode = 0664}, .show = setotgid_show, .store = setotgid_store, };*/ //setotgid的一致性，第一个参数setotgid和setotgid_show、setotgid_store前钻必须保持一致static DEVICE_ATTR(setotgid, 0664, setotgid_show, setotgid_store); //end zhaojr addstatic struct device_attribute *android_usb_attributes[] = { &dev_attr_state, &dev_attr_setotgid, //setotgid跟DEVICE_ATTR定义的name必须保持一致 NULL};

4、在probe()函数中定义针对具体GPIO管脚的请求和初始化

static int mdss_mdp_probe(struct platform_device *pdev){....................................................................................//zhaojr add for gpio134 to usb host or device mode ret_status=gpio_request(Gpio134_OtgID, 'Gpio134-OtgID'); if(ret_status<0){ pr_err('usb gadget configfs %s::Gpio134_OtgID gpio_request failedn',__func__); } pr_err('android_device_create()::Gpio134_OtgID gpio_request OKn'); gpio_direction_output(Gpio134_OtgID,1); if(otgid_status > 0){ //有自定义初始化状态就添加上这个判断，没有就不需要添加if else操作 pr_err('%s-Gpio134_OtgID pin set 1n', __func__); gpio_set_value(Gpio134_OtgID, 1); //msleep(5); }else{ pr_err('%s-Gpio134_OtgID pin set 0n', __func__); gpio_set_value(Gpio134_OtgID, 0); //msleep(5); } //end zhaojr add................................................................}

5、在remove()函数中添加资源的释放

static int mdss_mdp_remove(struct platform_device *pdev){ struct mdss_data_type *mdata = platform_get_drvdata(pdev); if (!mdata) return -ENODEV; pr_err('%sn', __func__); gpio_free(Gpio134_OtgID); //zhaojr add free gpio otgid pin ........................................................}

第二种方法：

在要添加驱动文件中没有搜索'DEVICE_ATTR'关键字的情况，如添加音频功放打开和关闭的控制接口：1、添加关键头文件：

#include <linux/of_gpio.h>#include <linux/gpio.h>#include <linux/delay.h>#include <linux/module.h>#include <linux/types.h>#include <linux/kobject.h>

2、定义全局变量和定义打开和关闭的接口并组织属性数组：

// add zhaojr gpio63 for close or speaker pa enablestruct kobject *spk_pa_kobj = NULL;unsigned int gpio63_spk_pa_gpio; //for speaker pa ic enable//extern unsigned int gpio63_spk_pa_gpio;static unsigned int SpkPa_Gpio_Enable = 0;static ssize_t spkpaon_store(struct device *dev, struct device_attribute *attr,const char *buf, size_t count) { unsigned int ret=0; //ret = kstrtoint(buf, 10, &backlight_enable); ret = kstrtouint(buf, 10, &SpkPa_Gpio_Enable); if (ret < 0){ pr_err('%s::kstrtouint() failed n', __func__); } pr_err('%s: SpkPa_Gpio_Enable=%d n', __func__,SpkPa_Gpio_Enable); if(SpkPa_Gpio_Enable > 0){ //gpio_set_value(gpio63_spk_pa_gpio, 1); pr_err('%s: gpio_set_value gpio63 speaker pa enable n', __func__); //功放打开的时序 gpio_set_value(gpio63_spk_pa_gpio,0); udelay(8); gpio_set_value(gpio63_spk_pa_gpio,1); udelay(8); gpio_set_value(gpio63_spk_pa_gpio,0); udelay(8); gpio_set_value(gpio63_spk_pa_gpio,1); //sdm660_cdc->ext_spk_pa_set = true; }else{ pr_err('%s: gpio_set_value gpio63 speaker pa disable n', __func__); //功放关闭的时序 gpio_set_value(gpio63_spk_pa_gpio,0); udelay(600); //sdm660_cdc->ext_spk_pa_set = false; } return count;}static ssize_t spkpaon_show(struct device *dev,struct device_attribute *attr, char *buf) { return sprintf(buf, '%dn',SpkPa_Gpio_Enable);} static DEVICE_ATTR(spkpaon, 0664, spkpaon_show, spkpaon_store);static struct attribute *spkpa_attributes[] = { &dev_attr_spkpaon.attr, NULL};static const struct attribute_group apkpa_attr_group = { .attrs = spkpa_attributes, NULL};//end zhaojr add

3、在probe()函数中添加文件系统属性接口的注册：在注册的时候并不需要对功放进行初始化，所以probe()函数中并没有对sdm660_cdc->spk_pa_gpio(GPIO63)，只操作了请求。具体的请求操作请参考：msm8953 audio部分的EAR和Speaker输出的声音配置中的音频部分的

vendor/qcom/opensource/audio-kernel/asoc/codecs/sdm660_cdc/msm-analog-cdc.c文件操作

static int msm_anlg_cdc_probe(struct platform_device *pdev){ int ret = 0; struct sdm660_cdc_priv *sdm660_cdc = NULL; struct sdm660_cdc_pdata *pdata; int adsp_state; .................................. dev_set_drvdata(&pdev->dev, sdm660_cdc); //kangting add sdm660_cdc->spk_pa_gpio = of_get_named_gpio(pdev->dev.of_node, 'qcom,speaker-pa', 0); if (!gpio_is_valid(sdm660_cdc->spk_pa_gpio)) pr_err('%s, sdm660_cdc->spk_pa_gpio not specifiedn',__func__); else{ pr_err('%s, sdm660_cdc->spk_pa_gpio is %dn',__func__,sdm660_cdc->spk_pa_gpio); ret = gpio_request(sdm660_cdc->spk_pa_gpio, 'spk_pa'); if (ret) { pr_err('request spk_pa_gpio failed, ret=%dn',ret); gpio_free(sdm660_cdc->spk_pa_gpio); } } //kangting end ret = snd_soc_register_codec(&pdev->dev, &soc_codec_dev_sdm660_cdc, msm_anlg_cdc_i2s_dai, ARRAY_SIZE(msm_anlg_cdc_i2s_dai)); if (ret) { dev_err(&pdev->dev, '%s:snd_soc_register_codec failed with error %dn', __func__, ret); goto err_supplies; } BLOCKING_INIT_NOTIFIER_HEAD(&sdm660_cdc->notifier); BLOCKING_INIT_NOTIFIER_HEAD(&sdm660_cdc->notifier_mbhc); //add by zhaojr gpio63_spk_pa_gpio = sdm660_cdc->spk_pa_gpio; //将设备树种定义的IO口号获取进来 spk_pa_kobj = kobject_create_and_add('spk_pa', NULL); //创建/sys/spk_pa/目录 ret = sysfs_create_group(spk_pa_kobj, &apkpa_attr_group); //创建/sys/class/spk_pa/spkpaon节点 if (ret) dev_err(&pdev->dev,'%s:sysfs_create_group failed with errorn',__func__); //end zhaojr add ....................................

4、在remove函数中释放资源

static int msm_anlg_cdc_remove(struct platform_device *pdev){ struct sdm660_cdc_priv *sdm660_cdc = dev_get_drvdata(&pdev->dev); struct sdm660_cdc_pdata *pdata = sdm660_cdc->dev->platform_data; int count; //add by zhaojr //释放资源 gpio_free(sdm660_cdc->spk_pa_gpio); kobject_put(spk_pa_kobj); //关键函数 sysfs_remove_group(spk_pa_kobj, &apkpa_attr_group); //关键函数 //end zhaojr add for (count = 0; count < sdm660_cdc->child_count && count < ANLG_CDC_CHILD_DEVICES_MAX; count++) platform_device_unregister( sdm660_cdc->pdev_child_devices[count]); snd_soc_unregister_codec(&pdev->dev); msm_anlg_cdc_disable_supplies(sdm660_cdc, pdata); wcd9xxx_spmi_irq_exit(); devm_kfree(&pdev->dev, sdm660_cdc); return 0;}

总结

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