Hi Alan,
> > Hi,
> >
> > I'm currently coding a device driver for a high speed device.
> > Unfortunately,
> > the test have shown, that the transfer rate is real slow.
> >
> > The code is as follows:
> >
> > urb = usb_alloc_urb( 0, GFP_KERNEL );
> > .....
> > usb_fill_bulk_urb( urb, usb_dev, pipe, data, len,
> > wcam_usb_api_blocking_completion, context
);
> > init_completion( &sbuf->done );
> > .....
> > urb->actual_length = 0;
> > status = usb_submit_urb(urb, GFP_ATOMIC);
> > .....
> > if ( status == 0 )
> > {
> >
> > wait_for_completion( &sbuf->done );
> >
> > }
> >
> > The memory to transfer is 307200 Bytes, the enpoint transfers up to
320
> > Byte.
> > BTW, is it possible to increase the Bulk transfersize beyond the 512
Bytes
> > ?
> Your question isn't clear. No, it's not possible for bulk endpoints to
> transfer more than 512 bytes per packet. Yes, it is possible for
> urb->transfer_length to be larger than 512 (the host controller driver
> will divide the data up into packets).
> > Now, what I get is, that the completion handler is called 960 times in
120
> > ms, which means
> > that the driver uses a single microframe to transfer 320 Bytes.
> I don't understand. The code above calls usb_submit_urb only once, so
the
> completion handler should be called only once. Not 960 times.
The urb is submitted again in the completion handler. If I understood
correctly, the completion
handler should be called once, when the transfer is completed.
static void wcam_usb_api_blocking_completion( struct urb *urb, struct
pt_regs *regs )
{
int nLength = urb->actual_length;
int nBufferSize = urb->transfer_buffer_length;
struct wcam_sbuf* sbuf = ( struct wcam_sbuf* ) urb->context;
PDEBUG (1,"Transferred %d Bytes of %d Bytes",nLength,nBufferSize);
if ( urb->status &&
!( urb->status == -ENOENT || urb->status == -ECONNRESET ||
urb->status == -ESHUTDOWN ) )
{
err( "ERROR: nRetVal=%d: %s", urb->status,
symbolic( m_stUrbErrorTextList, urb->status ) );
complete( &sbuf->done );
return ;
}
nBufferSize -= nLength;
urb->transfer_buffer_length = nBufferSize;
// Transferred all the data
if ( nBufferSize <= 0 )
{
complete( &sbuf->done );
return ;
}
urb->transfer_buffer += nLength;
/* Resubmit urb for new data */
urb->status = 0;
if ( usb_submit_urb(urb, GFP_ATOMIC) )
PDEBUG ( 0, "urb burned down in video irq" );
return ;
}
In my case I did it this way, because the completion handler was called
after 125 us and filled only 320 of 307200Bytes.
So I had no other choice, than to resubmit the urb.
I don't know why, the device did the transfer this way.
> > So my question is: How do I have to configure the bulk transfer to get
the
> > maximum speed ?
> In your code above, store all 307200 bytes in data and set len to
307200.
That was my very first approach.
Franz
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