综述
项目需求：客户有一个老化apk，自动测试闪光灯。
新增以下节点，控制闪光灯亮灭。
/sys/devices/virtual/torch/torch/torch_level
写入1 ，后手电筒亮
写入0 ，后手电筒灭
/sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
写入1 ，前手电筒亮
写入0 ，前手电筒灭
实现思路
1.创建/sys/devices/virtual/torch/torch/torch_level节点
2.在写入1的时候，打开闪光灯，写入0的时候，关闭闪光灯
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怎么在/sys/devices/virtual/路径下创建节点呢？很蒙逼
怎么在底层调用打开或者关闭闪光灯呢？很懵逼
学习本文，讲解决以上问题。
1.创建节点
这里以/sys/devices/virtual/torch/torch/torch_level节点创建为例子，
kernel-3.18/drivers/misc/mediatek/flashlight/src/mt6580/kd_flashlightlist.c
#define TORCH_DEVNAME "torch"//节点名称
static dev_t torch_devno;//设备号
static struct class *torch_class;//class类
static struct device *torch_device;//设备
static int main_torch_level = 0;
//show函数
static ssize_t torch_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
logI("zcf torch_show is call,main_torch_level=%d\n",main_torch_level);
return snprintf(buf, PAGE_SIZE, "%d\n", main_torch_level);
}
//store函数
static ssize_t torch_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
//添加闪光灯控制逻辑
return count;
}
//定义设备属性节点torch_level，和show函数，store函数
static DEVICE_ATTR(torch_level, S_IRUGO|S_IWUSR, torch_show, torch_store);
//初始化函数
static void torch_create(void)
{
int ret = 0;
logI("zcf [%s] is init\n",__func__);
//申请设备号--下面需要用的这个设备号
ret = alloc_chrdev_region(&torch_devno, 0, 1, TORCH_DEVNAME);
if (ret) {//申请成功
logI("zcf [torch_init] alloc_chrdev_region fail: %d ~", ret);
//goto torch_chrdev_error; 这里应该跳到unregister函数，懒得写
} else {//申请失败
logI("zcf [torch_init] major: %d, minor: %d ~", MAJOR(torch_devno),
MINOR(torch_devno));
}
//在sys/class创建torch_class 类
torch_class = class_create(THIS_MODULE, TORCH_DEVNAME);
if (IS_ERR(torch_class)) {//创建失败
logI("zcf Unable to create class:torch_class\n");
}
//在sys/class/torch_class/下创建设备节点
torch_device =device_create(torch_class, NULL, torch_devno,
NULL, TORCH_DEVNAME);
if(NULL == torch_device)//创建失败
logI("zcf [torch_init] device_create torch_device fail \n");
//在sys/class/torch_class/torch_class下创建属性文件torch_level
ret = device_create_file(torch_device,&dev_attr_torch_level);
if(ret < 0)
logI("zcf Failed to create attribute torch_levle\n");
}
static int flashlight_probe(struct platform_device *dev)
{
//省略代码
torch_create()；//创建节点
}
需要注意的地方
1.创建节点，最好在probe函数中创建！！！
2关于device_create_file函数
device_create_file(torch_device,&dev_attr_torch_level);
这个函数，前面的参数是device ，后面的参数加你要创建的节点名称dev_attr_xxxx。
device_create_file(torch_devicedev, &dev_attr_xxx);
dev_attr_xxx就是在xxx(要创建的节点)前加上dev_attr_
DEVICE_ATTR,device_create_file的使用
到此，我们的节点就创建出来了，有人可能会有疑问，上面代码中创建的节点是
sys/class/torch_class/torch_class/torch_level
但要求的节点路径是
/sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
不对劲啊！
实际上，我们创建sys/class/torch_class/torch_class/torch_level节点后，系统会默认也在/sys/devices/virtual/torch_class/torch_class/torch_level下创建一样的节点，使用adb命令可以查看！
（为啥会自动创建这个节点呢，这就需要跟踪源码啦）
adb命令查看节点
可以看到，确实系统默认创建了/sys/devices/virtual/torch_class/torch_class/torch_level节点。
2.打开、关闭 闪光灯
当我们获取torch_level节点的值(例如:使用adb命令 cat torch_level)时，就会调用show函数
//show函数
static ssize_t torch_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
logI("zcf torch_show is call,main_torch_level=%d\n",main_torch_level);
return snprintf(buf, PAGE_SIZE, "%d\n", main_torch_level);
}
当我们往torch_level节点写入值(例如:使用adb命令 echo 1 > torch_level)时，就会调用store函数
//store函数
static ssize_t torch_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
//添加闪光灯控制逻辑
return count;
}
因此，我们需要在store函数中添加闪光灯的控制逻辑，那么，如何打开或者关闭闪光灯呢？
kernel-3.18/drivers/misc/mediatek/flashlight/src/{平台}/{项目}/constant_flashlight/leds_strobe.c
int FL_Enable(void)//打开闪光灯
{
if (g_duty>=1)
{
mflash_set_gpio_output(GPIO_ENT,GPIO_OUT_ONE);
mflash_set_gpio_output(GPIO_ENF,GPIO_OUT_ONE);
FL_ALOGD(" FL_Enable enable in flash mode,duty=%d.", g_duty);
}
else
{
mflash_set_gpio_output(GPIO_ENT,GPIO_OUT_ONE);
mflash_set_gpio_output(GPIO_ENF,GPIO_OUT_ZERO);
FL_ALOGD(" FL_Enable enable in torch mode,duty=%d.", g_duty);
}
return 0;
}
int FL_Disable(void)//关闭闪关灯
{
FL_ALOGF();
mflash_set_gpio_output(GPIO_ENT,GPIO_OUT_ZERO);
mflash_set_gpio_output(GPIO_ENF,GPIO_OUT_ZERO);
return 0;
}
//初始化GPIO引脚
void main_camera_flash_gpio_init(void)
{
static struct device_node *main_flash_node;
FL_ALOGF();
main_flash_node = of_find_compatible_node(NULL, NULL,
"mediatek,mainflashlight");
GPIO_ENT = of_get_named_gpio(main_flash_node,
"flashlight_en_gpio", 0);
GPIO_ENF = of_get_named_gpio(main_flash_node,
"flashlight_mode_gpio", 0);
}
从源码中，可以看到，调用了FL_Enable和FL_Disable去打开、关闭闪光灯，原理就是通过拉高相应的GPIO脚，使能闪光灯，拉低GPIO脚，关闭闪光灯。
需要注意的是，每次调用之前，我们需要先调用GPIO初始化函数，找到相应的GPIO引脚
extern int FL_Enable(void);//声明FL_Enable是外部函数
extern int FL_Disable(void);
extern void main_camera_flash_gpio_init(void);
static ssize_t torch_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
int temp;
temp = simple_strtol(buf, NULL, 10);//把字符串转为数字
main_torch_level = temp;
main_camera_flash_gpio_init();//初始化gpio引脚
if(main_torch_level == 1)//如果写1
{
FL_Enable();//打开闪光灯
}
else if(main_torch_level == 0)//如果写0
FL_Disable();//关闭闪光灯
else//无效参数
logI("zcf invalid parameter,the torch_level must be 1 or 0\n");
logI("zcf main_torch_level=%d , count =%d\n",main_torch_level,count);
return count;
}
这样，我们在store函数中，就添加好了控制闪光灯的逻辑了。当然，仅仅这样，客户提供的第三方测试apk是无法访问节点的，会有selinux错误
avc: denied { write } for name="torch_level" dev="sysfs" ino=9205
scontext=u:r:system_app:s0 tcontext=u:object_r:sysfs:s0
tclass=file permissive=0
因此，我们要往系统加入相应的权限。
3.添加节点访问的权限
1.device/mediatek/mt6580/init.mt6580.rc
使所以用户对节点torch_level、sub_torch_level均有读写权限
# start-add by zcf in 2018.10.23 for torch_test
chmod 0666 /sys/devices/virtual/torch/torch/torch_level
chown root system /sys/devices/virtual/torch/torch/torch_level
chmod 0666 /sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
chown root system /sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
# end-add by zcf in 2018.10.23 for torch_test
2.device/mediatek/sepolicy/basic/non_plat/system_app.te
# add by zcf in 2018.10.23 for torch test
allow system_app sysfs:file { write read };
3.system/sepolicy/private/app.te
注释掉以下代码
以上这种添加SELinux权限的方式会导致GMS测试失败，因为改动了谷歌官方的逻辑-system/sepolicy/private/app.te。因此，换以下方式去改动：
1.device/mediatek/mt6580/init.mt6580.rc
使所以用户对节点torch_level、sub_torch_level均有读写权限
# start-add by zcf in 2018.10.23 for torch_test
chmod 0666 /sys/devices/virtual/torch/torch/torch_level
chown root system /sys/devices/virtual/torch/torch/torch_level
chmod 0666 /sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
chown root system /sys/devices/virtual/sub_torch/sub_torch/sub_torch_level
# end-add by zcf in 2018.10.23 for torch_test
2.自定义类型： 定义torch SELinux type
device/mediatek/sepolicy/bsp/non_plat/file.te
#add by zcf in 2018.11.1 for flashilight test
type system_app_torch_file,fs_type,sysfs_type;
type system_app_sub_torch_file,fs_type,sysfs_type;
3.file_contexts 绑定 torch对应的label
注意对应的节点是实际节点，而不是链接.以及整个目录路径中也绝不能包含链接(无数同仁有犯这个错误，特意提醒)
device/mediatek/sepolicy/bsp/non_plat/file_contexts
#add by zcf in 2018.11.01 for torch test
/sys/devices/virtual/torch/torch/torch_level u:object_r:system_app_torch_file:s0
/sys/devices/virtual/sub_torch/sub_torch/sub_torch_level u:object_r:system_app_sub_torch_file:s0
4.申请相关的权限
device/mediatek/sepolicy/basic/non_plat/system_app.te
# add by zcf in 2018.10.23 for torch test
allow system_app system_app_torch_file:file rw_file_perms;
allow system_app system_app_sub_torch_file:file rw_file_perms;
4.完整源码
kernel-3.18/drivers/misc/mediatek/flashlight/src/mt6580/kd_flashlightlist.c
//start-add by zcf in 2018.10.23 for torch test
#define TORCH_DEVNAME "torch"
#define SUB_TORCH_DEVNAME "sub_torch"
static dev_t torch_devno,sub_torch_devno;
static struct class *torch_class,*sub_torch_class;
static struct device *torch_device,*sub_torch_device;
extern void main_camera_flash_gpio_init(void);
extern void sub_camera_flash_gpio_init(void);
extern int FL_Enable(void);
extern int FL_Disable(void);
extern int FL_Sub_Enable(void);
extern int FL_Sub_Disable(void);
static int main_torch_level = 0;
static int sub_torch_level = 0;
static ssize_t torch_show(struct device *dev,struct device_attribute *attr, char *buf)
{
logI("zcf torch_show is call,main_torch_level=%d\n",main_torch_level);
return snprintf(buf, PAGE_SIZE, "%d\n", main_torch_level);
}
static ssize_t torch_store(struct device *dev,struct device_attribute *attr, const char *buf, size_t count)
{
int temp;
temp = simple_strtol(buf, NULL, 10);
main_torch_level = temp;
main_camera_flash_gpio_init();
if(main_torch_level == 1)
{
FL_Enable();
}
else if(main_torch_level == 0)
FL_Disable();
else
logI("zcf invalid parameter,the torch_level must be 1 or 0\n");
logI("zcf torch_store is call,main_torch_level=%d , count =%d\n",main_torch_level,count);
return count;
}
static DEVICE_ATTR(torch_level, S_IRUGO|S_IWUSR, torch_show, torch_store);
static ssize_t sub_torch_show(struct device *dev,struct device_attribute *attr, char *buf)
{
logI("zcf torch_show is call,main_torch_level=%d\n",main_torch_level);
return snprintf(buf, PAGE_SIZE, "%d\n", main_torch_level);
}
static ssize_t sub_torch_store(struct device *dev,struct device_attribute *attr, const char *buf, size_t count)
{
int temp;
temp = simple_strtol(buf, NULL, 10);
sub_torch_level = temp;
sub_camera_flash_gpio_init();
if(sub_torch_level == 1)
{
FL_Sub_Enable();
}
else if(sub_torch_level == 0)
FL_Sub_Disable();
else
logI("zcf invalid parameter,the sub_torch_level must be 1 or 0\n");
logI("zcf torch_store is call,sub_torch_level=%d , count =%d\n",sub_torch_level,count);
return count;
}
static DEVICE_ATTR(sub_torch_level, S_IRUGO|S_IWUSR, sub_torch_show, sub_torch_store);
static void torch_create(void)
{
int ret = 0;
logI("zcf [%s] is init\n",__func__);
ret = alloc_chrdev_region(&torch_devno, 0, 1, TORCH_DEVNAME);
if (ret) {
logI("zcf [torch_init] alloc_chrdev_region fail: %d ~", ret);
//goto torch_init_error;
} else {
logI("zcf [torch_init] major: %d, minor: %d ~", MAJOR(torch_devno),
MINOR(torch_devno));
}
ret = alloc_chrdev_region(&sub_torch_devno, 0, 1, SUB_TORCH_DEVNAME);
if (ret) {
logI("zcf [torch_init] alloc_chrdev_region fail: %d ~", ret);
//goto torch_init_error;
logI("zcf [torch_init] major: %d, minor: %d ~", MAJOR(sub_torch_devno),
MINOR(sub_torch_devno));
}
torch_class = class_create(THIS_MODULE, TORCH_DEVNAME);
if (IS_ERR(torch_class)) {
logI("zcf Unable to create class:torch_class\n");
}
torch_device =device_create(torch_class, NULL, torch_devno, NULL, TORCH_DEVNAME);
if(NULL == torch_device)
logI("zcf [torch_init] device_create torch_device fail \n");
ret = device_create_file(torch_device,&dev_attr_torch_level);
if(ret < 0)
logI("zcf Failed to create attribute torch_levle\n");
sub_torch_class = class_create(THIS_MODULE, SUB_TORCH_DEVNAME);
if (IS_ERR(sub_torch_class)) {
logI("zcf Unable to create class:sub_torch_class\n");
}
sub_torch_device =device_create(sub_torch_class, NULL, sub_torch_devno, NULL, SUB_TORCH_DEVNAME);
if(NULL == sub_torch_device)
logI("zcf [torch_init] device_create torch_device fail \n");
ret = device_create_file(sub_torch_device,&dev_attr_sub_torch_level);
if(ret < 0)
logI("zcf Failed to create attribute sub_torch_levle\n");
}
//end-add by zcf in 2018.10.23 for torch test.
static int flashlight_probe(struct platform_device *dev)
{
int ret = 0, err = 0;
logI("[flashlight_probe] start ~")
//省略部分代码
torch_create();
}
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