Re: WriteFile(...) to USB HID: why does this call hang my client application ?

"Robert Marquardt" <> wrote in message
news:...
| > But I'm stumbling with some issues when sending
| > reports with WriteFile. I never get any error
| > results ( WriteFile() returns a non-zero value ),
| > but sometimes the call just doesn't return,
| > and requires me to kill my application.
| >
| > Any idea why this would be happening ?
|
| Try using separate file handles for read and write.

Thanks for the tip.
I tried using a separate Handle for input and output
(from two calls to CreateFile). But no luck.

The USB device receives a first series of Reports,
but then the PC client enters a deadlock. I pause
the client in the debugger and get the message:
The process appears to be deadlocked
(or is not running any user-mode code).
All threads have been stopped.
I only have 1 thread, which is blocked on a call
to WriteFile which never does return.

Any other idea/suggestion ?



tia
--
Ivan Vecerina, Dr. med. <> http://www.post1.com/~ivec

Ivan Vecerina wrote:

> I only have 1 thread, which is blocked on a call
> to WriteFile which never does return.

Blocking on WriteFile for USB is strange indeed.
It may be a bad driver. For now i have no further help to offer.

"Robert Marquardt" <> wrote in message
news:...
| Ivan Vecerina wrote:
|
| > I only have 1 thread, which is blocked on a call
| > to WriteFile which never does return.
|
| Blocking on WriteFile for USB is strange indeed.
| It may be a bad driver. For now i have no further help to offer.

I was able to trace the problem down to our custom USB device,
which failed to reply(acknowledge) the output report it received.

I still find it disturbing, though, that the WriteFile call just
hangs and never returns (Win2k SP4) -- instead of reporting
an error after some timeout...

Issue solved now anyway.

Many thanks for your advice !
Ivan

--
http://www.post1.com/~ivec

Ivan Vecerina wrote:

> I was able to trace the problem down to our custom USB device,
> which failed to reply(acknowledge) the output report it received.
>
> I still find it disturbing, though, that the WriteFile call just
> hangs and never returns (Win2k SP4) -- instead of reporting
> an error after some timeout...

You expect here too much from software. Handling a hardware failure is
not an easy task.