Hi,all
I'm writing a linux usb driver for our data sampling board which
transmit data with usb bus. I didn't write a host usb driver under linux
before.
I need to send some vendor request to the board to tell it how to work.
Such as , when some one open the device , the driver need to
tell board to start sample.I write the open method like this:
struct usb_ctrlrequest start_ad_convert_quest =
{
.bRequestType = USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
.bRequest = AD_BREQUEST_START_CONVERT,
.wValue = 0,
.wIndex = 0,
.wLength = 0,
};
static int ad_open(struct inode *inode, struct file *file)
{
[snip]
if(0 == dev->started){
ctrl_urb = usb_alloc_urb(0, GFP_KERNEL);
if(NULL == ctrl_urb){
retval = -ENOMEM;
goto exit;
}
usb_fill_control_urb(ctrl_urb, dev->udev, usb_sndctrlpipe(dev->udev, 0),
(unsigned char*)&start_ad_convert_quest, NULL, 0,
ctrl_urb_finish, dev);
retval = usb_submit_urb (ctrl_urb, GFP_KERNEL);
if (0 > retval){
ERROR("Can't submit start_convert request\n");
}
}
[snip]
}
static void ctrl_urb_finish(struct urb* ctrl_urb, struct pt_regs *reg)
{
[snip]
if(0 != ctrl_urb->status){
ERROR("Start convert request hasn't been sent successfully:%d\n",
ctrl_urb->status);
goto exit;
}
[snip]
exit:
usb_free_urb(ctrl_urb);
}
If I do like the above , I will always get ctrl_urb->status =
-32(-EPIPE),and I can only open the device node once
.When I open the node the second time , the HDD led indicate that
harddisk is busy, no output of printk,after about one
minute later ,the host desktop is dead ,no response, I have to reboot
it.I try to change the memory allocating flags from GFP_KERNEL
to GFP_NOIO or GFP_ATOMIC, the result is same.
But if I don't use urb directly, ie, using :
usb_control_msg(dev->udev,usb_sndctrlpipe(dev->udev,
0),AD_BREQUEST_START_CONVERT,USB_DIR_OUT | USB_TYPE_VENDOR |
USB_RECIP_DEVICE,0,0,NULL,0,1000);
It works fine , every thing is right.
What's the possible reason?Any advices are welcome. Thanks
Regards
twomol
3.22
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