解析linux或android添加文件系统的属性接口的方法

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, %d\n ,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 add
static 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 failed\n",__func__); 

 pr_err("android_device_create()::Gpio134_OtgID gpio_request OK\n"); 

 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 1\n", __func__);

 gpio_set_value(Gpio134_OtgID, 1); 

 //msleep(5);

 }else{

 pr_err("%s-Gpio134_OtgID pin set 0\n", __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( %s\n , __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 enable
struct 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, %d\n ,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 specified\n ,__func__);
else{
pr_err( %s, sdm660_cdc- spk_pa_gpio is %d\n ,__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=%d\n ,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 %d\n ,
__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 error\n ,__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;

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