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Hi,

I have the code below to write some data to a bulk usb output endpoint
using the sync api.

// Find device
// Write data
do {
  r = libusb_bulk_transfer(handle, endpoint_out, wdata, swdata, &size,
1000);
  if (r == LIBUSB_ERROR_PIPE) {
    libusb_clear_halt(handle, endpoint_out);
  }
  i++;
} while ((r == LIBUSB_ERROR_PIPE) && (i<RETRY_MAX));

// Read response
int rsize;
char rdata[srdata] = {0};
r = libusb_bulk_transfer(handle, endpoint_in, &rdata, srdata, &rsize, 1000);
if (r < 0)
{
  printf("libusb_bulk_transfer failed: %s\n", libusb_error_name(r));
}

How could I achieve the same with the async api? I have tried the code
below, but I do not seem to get the same data back.

  struct libusb_transfer *transfer = libusb_alloc_transfer(0);
  libusb_fill_bulk_transfer(transfer, handle, endpoint_out, wdata, swdata,
cb_write, NULL, 0);
  if (libusb_submit_transfer(transfer) < 0)
        printf("Failed to submit the read command.");
  while (1) {
    r = libusb_handle_events(context);
    if (r < 0)
      printf("Failed to handle events\n");
    }

Then, in the write callback:

static void cb_write(struct libusb_transfer *transfer)
{
    if (transfer->status != LIBUSB_TRANSFER_COMPLETED) {
        fprintf(stderr, "Write transfer status %d?\n", transfer->status);
        libusb_free_transfer(transfer);
        transfer = NULL;
        return;
    }

struct libusb_transfer *read_transfer = libusb_alloc_transfer(0);
libusb_fill_bulk_transfer(read_transfer, handle, endpoint_in, rdata,
srdata, cb_ready, NULL, 0);
if (libusb_submit_transfer(read_transfer) < 0)
   printf("Failed to submit the read operation.\n");
else
  printf("Submitted the read operation.\n");

Then, I was thinking that I would need to do something for a read callback:

static void cb_read(struct libusb_transfer *transfer)
{
    if (transfer->status != LIBUSB_TRANSFER_COMPLETED) {
        fprintf(stderr, "Read transfer status: %d, data length: %d\n",
transfer->status, transfer->length);
        libusb_free_transfer(transfer);
        transfer = NULL;
        return;
    }

    if (libusb_submit_transfer(transfer) < 0)
       printf("Failed to submit the transfer\n");
}

So, I guess the real question is whether I am meant to handle the situation
of write a request and then read the response in this way with the async
libusb api or somehow different.

Kind regards,
Laszlo Papp

PS.: I got most of this logic from the examples.

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<div dir=3D"ltr">Hi,<div><br></div><div>I have the code below to write some=
 data to a bulk usb output endpoint using the sync api.</div><div><br></div=
><div>// Find device</div><div>// Write data</div><div>do {<br></div><div>=
=C2=A0 r =3D libusb_bulk_transfer(handle, endpoint_out, wdata, swdata, &amp=
;size, 1000);<br>=C2=A0 if (r =3D=3D LIBUSB_ERROR_PIPE) {<br>=C2=A0 =C2=A0 =
libusb_clear_halt(handle, endpoint_out);<br>=C2=A0 }<br>=C2=A0 i++;<br>			}=
 while ((r =3D=3D LIBUSB_ERROR_PIPE) &amp;&amp; (i&lt;RETRY_MAX));<br><br>/=
/ Read response<br>int rsize;<br>			char rdata[srdata] =3D {0};<br>			r =3D=
 libusb_bulk_transfer(handle, endpoint_in, &amp;rdata, srdata, &amp;rsize, =
1000);<br>			if (r &lt; 0)<br>			{<br>=C2=A0 printf(&quot;libusb_bulk_trans=
fer failed: %s\n&quot;, libusb_error_name(r));<br>			}</div><div><br></div>=
<div>How could I achieve the same with the async api? I have tried the code=
 below, but I do not seem to get the same data back.</div><div><br></div><d=
iv>=C2=A0 struct libusb_transfer *transfer =3D libusb_alloc_transfer(0);<br=
>=C2=A0 libusb_fill_bulk_transfer(transfer, handle, endpoint_out, wdata, sw=
data, cb_write, NULL, 0); <br>=C2=A0 if (libusb_submit_transfer(transfer) &=
lt; 0)<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 printf(&quot;Failed to submit the rea=
d command.&quot;);<br>=C2=A0 while (1) {<br>=C2=A0 =C2=A0 r =3D libusb_hand=
le_events(context);<br>=C2=A0 =C2=A0 if (r &lt; 0)<br>=C2=A0 =C2=A0 =C2=A0 =
printf(&quot;Failed to handle events\n&quot;);<br>=C2=A0 =C2=A0 }<br></div>=
<div><br></div><div>Then, in the write=C2=A0callback:</div><div><br></div><=
div>static void cb_write(struct libusb_transfer *transfer)<br>{<br>=C2=A0 =
=C2=A0 if (transfer-&gt;status !=3D LIBUSB_TRANSFER_COMPLETED) {<br>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0 fprintf(stderr, &quot;Write transfer status %d?\n&quot=
;, transfer-&gt;status);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 libusb_free_transfe=
r(transfer);<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 transfer =3D NULL;<br>=C2=A0 =
=C2=A0 =C2=A0 =C2=A0 return;<br>=C2=A0 =C2=A0 } =C2=A0 <br><br>struct libus=
b_transfer *read_transfer =3D libusb_alloc_transfer(0);<br>libusb_fill_bulk=
_transfer(read_transfer, handle, endpoint_in, rdata, srdata, cb_ready, NULL=
, 0);<br>	if (libusb_submit_transfer(read_transfer) &lt; 0)<br>	 =C2=A0 =C2=
=A0printf(&quot;Failed to submit the read operation.\n&quot;);<br>	else<br>=
=C2=A0 printf(&quot;Submitted the read operation.\n&quot;);<br><br>Then, I =
was thinking that I would need to do something for a read callback:</div><d=
iv><br></div><div>static void cb_read(struct libusb_transfer *transfer)<br>=
{<br>=C2=A0 =C2=A0 if (transfer-&gt;status !=3D LIBUSB_TRANSFER_COMPLETED) =
{<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 fprintf(stderr, &quot;Read transfer status=
: %d, data length: %d\n&quot;, transfer-&gt;status, transfer-&gt;length);<b=
r>=C2=A0 =C2=A0 =C2=A0 =C2=A0 libusb_free_transfer(transfer);<br>=C2=A0 =C2=
=A0 =C2=A0 =C2=A0 transfer =3D NULL;<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 return;=
<br>=C2=A0 =C2=A0 } =C2=A0 <br><br>=C2=A0 =C2=A0 if (libusb_submit_transfer=
(transfer) &lt; 0)<br>=C2=A0 =C2=A0 =C2=A0 =C2=A0printf(&quot;Failed to sub=
mit the transfer\n&quot;);<br>}</div><div><br></div><div>So, I guess the re=
al question is whether I am meant to handle the situation of write a reques=
t and then read the response in this way with the async libusb api or someh=
ow different.</div><div><br></div><div>Kind regards,</div><div>Laszlo Papp<=
/div><div><br></div><div>PS.: I got most of this logic from the examples.<b=
r><br></div></div>

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