In davinci_doioctl:
case VIDIOC_DQBUF:
The function videobuf_dqbuf will call another function named videobuf_waiton:
int videobuf_waiton(struct videobuf_buffer *vb, int non_blocking, int intr)
{
int retval = 0;
struct timeval uTimeStart, uTimeStop;
unsigned long timeDelta;
DECLARE_WAITQUEUE(wait, current);
MAGIC_CHECK(vb->magic,MAGIC_BUFFER);
add_wait_queue(&vb->done, &wait);
while (vb->state == STATE_ACTIVE || vb->state == STATE_QUEUED) {
if (non_blocking) {
retval = -EAGAIN;
break;
}
set_current_state(intr ? TASK_INTERRUPTIBLE: TASK_UNINTERRUPTIBLE);
printk("22222vb->state=%d\n",vb->state);
if (vb->state == STATE_ACTIVE || vb->state == STATE_QUEUED){
do_gettimeofday(&uTimeStart);
schedule();
do_gettimeofday(&uTimeStop);
timeDelta = (unsigned long)((uTimeStop.tv_sec-uTimeStart.tv_sec)*1000000+(uTimeStop.tv_usec-uTimeStart.tv_usec));
printk("schedule: %ld ms\n",timeDelta/1000);
}
set_current_state(TASK_RUNNING);
if (intr && signal_pending(current)) {
dprintk(1,"buffer waiton: -EINTR\n");
retval = -EINTR;
break;
}
}
remove_wait_queue(&vb->done, &wait);
return retval;
}
Can anybody tell me the usage of this function and in what case that the vb->state == STATE_ACTIVE ,because in my programme ,the vb->state is always STATE_ACTIVE , i don't known why ?
In my opinion , this function is used to wait a usable buffer , is it right ?
Any advice will be appreciate .
regards,
Katee
