libusb_control_transfer(devh, 0x81, USB_RQ, 0xf0, 0, data, sizeof(data), 0) hangs .

[liuwang]

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[Segher Boessenkool]

> static int print_f0_data(void)
> {
>   unsigned char data[0x10];
>   int r;
>   unsigned int i;
>   if (r < 0)

You forgot to assign anything to r; did you delete that when
writing this mail?


Segher


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[Michael Plante]

liuwang wrote:
>> During porting our USB LCD to libusb-1.0 libusb_control_transfer(devh,
0x81,
>> USB_RQ, 0xf0, 0, data, sizeof(data), 0) hangs in print_f0_data(void).

The call to this libusb_control_transfer seems to be missing.  Also, in
print_f0_data, r looks uninitialized.

Regards,
Michael


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[liuwang]

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[Tim Roberts]

Liu Wang wrote:
> Michael,
>
> Thanks the help.
> "r=1" is deleted in the email.

No, that's not right.  I'm pretty certain the line that you removed was
this:
   r = libusb_control_transfer( devh, 0x81, USB_RQ, 0xf0, 0, data
sizeof(data), 0 );

Without that, your code doesn't make any sense.

By the way, what do you think that code is doing?  You didn't tell us
what the value of USB_RQ is, so we can't be certain what you're doing,
but this looks like you're trying to do a HID output report.  Does your
device support this kind of operation?

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Providenza & Boekelheide, Inc.


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[liuwang]

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[Tim Roberts]

liuwang wrote:

>
> Appreciate the help.
>
> You are right.
>
> The following was removed by accident.
>
>    r = libusb_control_transfer( devh, 0x81, USB_RQ, 0xf0, 0, data
> sizeof(data), 0 );
>
> And USB_RQ was defined as :
>
> #define USB_RQ 0x06 // get device descriptor.
>
>  
>
> Our small character LCD module supports the operation when using
> libusb 0.1 and we are updating it to libusb-1.0.
>

So that's a request to fetch a HID-class-specific descriptor.  A wValue
of 0x00F0 is not legal for that kind of request.  Is this some custom
extension that your device provides?

--
Tim Roberts, [hidden email]
Providenza & Boekelheide, Inc.


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