libusb-devel

[Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[He.David <Dav...@IG...>]

Hi, Does anyone can help me to figure out why I got this compiler error? How to pass the call back function in this case?

void transfer_cb_fn (libusb_transfer* transfer){
  cout<<"call back function called"<<endl;
}

Void main(...){
...
  libusb_transfer* transfer;
  libusb_fill_interrupt_transfer (transfer, dev_handle, 129, data, 20, transfer_cb_fn,  user_data, 10000);

}

Error message:
error C2664: 'libusb_fill_interrupt_transfer' : cannot convert parameter 6 from 'void (__cdecl *)(libusb_transfer *)' to 'libusb_transfer_cb_fn'
2>        None of the functions with this name in scope match the target type



Thanks.

David

Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[Tim R. <ti...@pr...>]

He.David wrote:
>
> Hi, Does anyone can help me to figure out why I got this compiler
> error? How to pass the call back function in this case?
>
>  
>
> voidtransfer_cb_fn (libusb_transfer* transfer){
>
>   cout<<"call back function called"<<endl;
>
> }
>
>  
>
> Void main(…){
>
> …
>
>   libusb_transfer* transfer;
>
>   libusb_fill_interrupt_transfer (transfer, dev_handle, 129, data, 20,
> transfer_cb_fn,  user_data, 10000);
>
>  
>
> }
>
>  
>
> Error message:
>
> error C2664: 'libusb_fill_interrupt_transfer' : cannot convert
> parameter 6 from 'void (__cdecl *)(libusb_transfer *)' to
> 'libusb_transfer_cb_fn'
>
> 2>        None of the functions with this name in scope match the
> target type
>

Try declaring it as C linkage:

    extern "C" void cb_fn( libusb_transfer* transfer );

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.

Re: [Libusb-devel] how to usefunction libusb_fill_interrupt_transfer(...)

[Michael P. <mic...@gm...>]

Tim Roberts wrote:
>> > Error message:
>> >
>> > error C2664: 'libusb_fill_interrupt_transfer' : cannot convert
>> > parameter 6 from 'void (__cdecl *)(libusb_transfer *)' to
>> > 'libusb_transfer_cb_fn'
>> >
>> > 2>        None of the functions with this name in scope match the
>> > target type
>> >
>>
>> Try declaring it as C linkage:
>>
>>     extern "C" void cb_fn( libusb_transfer* transfer );


You probably need that too if you're doing C++, but you definitely need the
proper calling convention, as specified both in the definition of
libusb_transfer_cb_fn in libsub.h (see the error message you pasted):

	   typedef void (LIBUSB_CALL *libusb_transfer_cb_fn)(struct libusb_transfer
*transfer);

AND in the examples, such as dpfp.c:

	   static void LIBUSB_CALL cb_irq(struct libusb_transfer *transfer)

	   libusb_fill_interrupt_transfer(irq_transfer, devh, EP_INTR, irqbuf,
sizeof(irqbuf), cb_irq, NULL, 0);

(the static part isn't necessarily needed; that's your choice)

Michael

Re: [Libusb-devel] how to usefunction libusb_fill_interrupt_transfer(...)

[Michael P. <mic...@gm...>]

Michael Plante wrote:
>> typedef void (LIBUSB_CALL *libusb_transfer_cb_fn)(struct libusb_transfer
*transfer);

Hrm, interestingly:

http://libusb.sourceforge.net/api-1.0/group__asyncio.html#ga62afeef38ae1003e
14d2e8eb06462f25

leaves out the LIBUSB_CALL.  The last doxygen run was Apr 19 2010.  Now
1.0.8 didn't include this change, but, even so, the 1.0.8 tag is dated May 4
2010.  Should we try to keep doxygen up to releases or to latest git?  Note
that this change *is* in libusb.git, even though libusb.git isn't quite
right for Windows yet.


>> in libsub.h

(and of course that's a typo)

Michael

Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[Peter S. <pe...@st...>]

Tim Roberts wrote:
> > Error message:
> >
> > error C2664: 'libusb_fill_interrupt_transfer' : cannot convert
> > parameter 6 from 'void (__cdecl *)(libusb_transfer *)' to
> > 'libusb_transfer_cb_fn'
..
> Try declaring it as C linkage:
> 
>     extern "C" void cb_fn( libusb_transfer* transfer );

Throw in a LIBUSB_CALL there as well.


//Peter

Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[He.David <Dav...@IG...>]

Thanks for the help. It passes the complier; but the call back function never got called; does anyone know how come the call back function never got called?

static void LIBUSB_CALL transfer_cb_fn (struct libusb_transfer* transfer){
  cout<<"call back function called"<<endl;
}

Void main(...){

...
	 libusb_fill_interrupt_transfer (transfer, dev_handle, 0x81, 
		 data, sizeof(data), transfer_cb_fn, NULL, 0);
	 
	 libusb_submit_transfer(transfer);
...

}
Thanks.


David

-----Original Message-----
From: Peter Stuge [mailto:pe...@st...] 
Sent: Monday, January 24, 2011 6:17 PM
To: lib...@li...
Subject: Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

Tim Roberts wrote:
> > Error message:
> >
> > error C2664: 'libusb_fill_interrupt_transfer' : cannot convert
> > parameter 6 from 'void (__cdecl *)(libusb_transfer *)' to
> > 'libusb_transfer_cb_fn'
..
> Try declaring it as C linkage:
> 
>     extern "C" void cb_fn( libusb_transfer* transfer );

Throw in a LIBUSB_CALL there as well.


//Peter

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Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[Peter S. <pe...@st...>]

He.David wrote:
> Thanks for the help. It passes the complier; but the call back
> function never got called; does anyone know how come the call back
> function never got called?

Are you doing event handling? Please have a look at the 1.0 API docs
for more details. Feel free to ask if something is unclear.


//Peter

Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[Alan S. <st...@ro...>]

On Tue, 25 Jan 2011, He.David wrote:

> Thanks for the help. It passes the complier; but the call back function never got called; does anyone know how come the call back function never got called?
> 
> static void LIBUSB_CALL transfer_cb_fn (struct libusb_transfer* transfer){
>   cout<<"call back function called"<<endl;
> }
> 
> Void main(...){
> 
> ...
> 	 libusb_fill_interrupt_transfer (transfer, dev_handle, 0x81, 
> 		 data, sizeof(data), transfer_cb_fn, NULL, 0);
> 	 
> 	 libusb_submit_transfer(transfer);
> ...
> 
> }

Maybe your callback function never gets called because the transfer 
never completes.  In other words, maybe the device never sends any 
interrupt packets.

You could find out what's happening by using a USB sniffer program.

Alan Stern

Re: [Libusb-devel] how to use function libusb_fill_interrupt_transfer(...)

[Segher B. <se...@ke...>]

>> static void LIBUSB_CALL transfer_cb_fn (struct libusb_transfer*
>> transfer){
>>   cout<<"call back function called"<<endl;
>> }
>>
>> Void main(...){
>>
>> ...
>> 	 libusb_fill_interrupt_transfer (transfer, dev_handle, 0x81,
>> 		 data, sizeof(data), transfer_cb_fn, NULL, 0);
>>
>> 	 libusb_submit_transfer(transfer);
>> ...
>>
>> }
>
> Maybe your callback function never gets called because the transfer
> never completes.  In other words, maybe the device never sends any
> interrupt packets.

It sounds more like he never calls libusb_handle_events() or similar.


Segher