【发布时间】：2017-12-17 17:55:41
【问题描述】：
我的 raspi 内核模块，为获得双光屏障而编写，如果两个输入 gpio 的边缘中的每一个都在上升并且发生中断，则读取单调时间。时间值通过普通的 sysfs 文件传递给用户空间（不是开发文件）。这工作正常。
我的用户空间实现应该读取这些值并计算对象通过光栅的最终速度。这目前通过定期读取 sysfs 文件来解决。如果值发生变化，则会选取并使用新值。
为了节省资源，我想在相关的 sysfs 文件上为 POLLPRI 进行 poll()。在内核模块内部应该有一个 sysfs_notify() 向用户空间提供相关 sysfs 文件的更改状态和值。
但我在用户空间中的 poll() 会永久阻塞。我也尝试将 POLLIN 作为事件。结果是 poll() 函数立即返回。
这是我的代码...
// [...]
static struct kobject *gpio; // dir /sys/kernel/gpio
static ssize_t gpio17s_show(struct kobject *kobj,struct kobj_attribute
*attr,char *buf)
{
return sprintf(buf,"%li",sec1);
}
static ssize_t gpio17s_store(struct kobject *kobj,struct kobj_attribute
*attr,const char *buf,size_t count)
{
sscanf(buf,"%li",&sec1);
return count;
}
}
// [...] (two more files)
static ssize_t gpio26n_show(struct kobject *kobj,struct kobj_attribute
*attr,char *buf)
{
sysfs_notify(gpio,NULL,"gpio26n"); // Is this the right place, the right invocation????
// I saw this already in isr, but i believe this is not a good idea....
// Has it perhaps to be in module_init function???
// First arg('gpio') is kobject of the dir containing files(attributes)..
// This can not be right in my mind, but how do I find the right kobj??
// The third param 'gpio26n' if the file, on which I'm polling.
return sprintf(buf,"%li",nsec2);
}
static ssize_t gpio26n_store(struct kobject *kobj,struct kobj_attribute
*attr,const char *buf,size_t count)
{
sscanf(buf,"%li",&nsec2);
return count;
}
static int cleanup(int value,int ret) {
switch(value) {
case 5:
free_irq(speed_irq2,NULL);
case 4:
free_irq(speed_irq1,NULL);
case 3:
gpio_free(PIN2);
case 2:
gpio_free(PIN1);
case 1:
kobject_put(gpio);
}
return ret;
}
static irqreturn_t speed_isr(int irq, void *data) {
if(irq==speed_irq1) {
getrawmonotonic(&ts1);
sec1=ts1.tv_sec;
nsec1=ts1.tv_nsec;
}
if(irq==speed_irq2) {
getrawmonotonic(&ts2);
sec2=ts2.tv_sec;
nsec2=ts2.tv_nsec;
}
return IRQ_HANDLED;
}
static struct kobj_attribute gpio17s_attr = __ATTR(gpio17s,0644,
gpio17s_show,gpio17s_store);
static struct kobj_attribute gpio26n_attr = __ATTR(gpio26n,0644,
gpio26n_show,gpio26n_store);
static int __init d_init(void) {
int ret=0;
printk(KERN_INFO "Module successfully loaded...");
gpio=kobject_create_and_add("gpio",kernel_kobj);
if(!gpio) {
printk(KERN_ERR "Failed to create 'gpio'");
return -ENOMEM;
}
ret=sysfs_create_file(gpio,&gpio17s_attr.attr);
if(ret) {
printk(KERN_ERR "Failed to create file 'gpio17s'");
return cleanup(1,2);
}
// [...] (two more files)
ret=sysfs_create_file(gpio,&gpio26n_attr.attr);
if(ret) {
printk(KERN_ERR "Failed to create file 'gpio26n'");
return cleanup(1,5);
}
ret=gpio_request(PIN1,"gpio 17");
if(ret) {
printk(KERN_ERR "Failed to request 'gpio17'");
return cleanup(1,6);
}
ret=gpio_request(PIN2,"gpio 26");
if(ret) {
printk(KERN_ERR "Failed to request 'gpio26'");
return cleanup(2,7);
}
ret=gpio_to_irq(PIN1);
if(ret<0) {
printk(KERN_ERR "Unable to get irq for pin 17");
return cleanup(3,8);
}
speed_irq1=ret;
ret=gpio_to_irq(PIN2);
if(ret<0) {
printk(KERN_ERR "Unable to get irq for pin 26");
return cleanup(3,9);
}
speed_irq2=ret;
ret=request_irq(speed_irq1,speed_isr,IRQF_TRIGGER_RISING,
"Speed trigger 17",NULL);
if(ret) {
printk(KERN_ERR "Unable to request irq for pin 17");
return cleanup(3,10);
}
ret=request_irq(speed_irq2,speed_isr,IRQF_TRIGGER_RISING,
"Speed trigger 26",NULL);
if(ret) {
printk(KERN_ERR "Unable to request irq for pin 26");
return cleanup(4,10);
}
return 0;
}
static void __exit d_exit(void) {
// [...]
还有我的用户空间应用程序
// [...]
int main() {
int f ;
char buf[16];
struct pollfd pfd ;
while(1) {
memset(buf,0,sizeof(buf));
if((f=open("/sys/kernel/gpio/gpio26n",O_RDONLY)) <0) {
fprintf(stderr,"Failed to open sysfs file\n");
exit(1);
}
if((lseek(f,0L,SEEK_SET)) <0) {
fprintf(stderr,"Failed to set pointer\n");
exit(2);
}
if((read(f,buf,1)) <0) {
fprintf(stderr,"Failed to read from file\n");
exit(3);
}
pfd.fd = f ;
pfd.events = POLLPRI;
poll(&pfd,1,-1); // This should block until value has changed....
close(f);
// fopen, read new value etc.
// [...]
// Do some stuff, calculate speed, etc
}
}
你好
【问题讨论】：
标签： c linux-kernel sysfs