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, "%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 = http://www.cppcns.com/os/linux/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解析linux或android添加文件系统的属性接口的方法
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