Re: [PATCH] usb: dwc2: host: fix isoc urb actual length

[wlf]

Hi Minas,

å 2017å11æ06æ 17:28, Minas Harutyunyan åé:
> Hi,
>
> On 11/6/2017 12:46 PM, William Wu wrote:
> > The actual_length in dwc2_hcd_urb structure is used
> > to indicate the total data length transferred so far,
> > but in dwc2_update_isoc_urb_state(), it just updates
> > the actual_length of isoc frame, and don't update the
> > urb actual_length at the same time, this will cause
> > device drivers working error which depend on the urb
> > actual_length.
> >
> > we can easily find this issue if use an USB cameraï
> > the userspace use libusb to get USB data from kernel
> > via devio driver.In usb devio driver, processcompl()
> > function will process urb complete and copy data to
> > userspace depending on urb actual_length.
> >
> > Let's update the urb actual_length if the isoc frame
> > is valid.
> >
> > Signed-off-by: William Wu <william.wu@xxxxxxxxxxxxxx>
> > ---
> >    drivers/usb/dwc2/hcd_intr.c | 2 ++
> >    1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
> > index 28a8210..01b1e13 100644
> > --- a/drivers/usb/dwc2/hcd_intr.c
> > +++ b/drivers/usb/dwc2/hcd_intr.c
> > @@ -580,6 +580,7 @@ static enum dwc2_halt_status dwc2_update_isoc_urb_state(
> >    		frame_desc->status = 0;
> >    		frame_desc->actual_length = dwc2_get_actual_xfer_length(hsotg,
> >    					chan, chnum, qtd, halt_status, NULL);
> > +		urb->actual_length += frame_desc->actual_length;
> >    		break;
> >    	case DWC2_HC_XFER_FRAME_OVERRUN:
> >    		urb->error_count++;
> > @@ -599,6 +600,7 @@ static enum dwc2_halt_status dwc2_update_isoc_urb_state(
> >    		frame_desc->status = -EPROTO;
> >    		frame_desc->actual_length = dwc2_get_actual_xfer_length(hsotg,
> >    					chan, chnum, qtd, halt_status, NULL);
> > +		urb->actual_length += frame_desc->actual_length;
> >    
> >    		/* Skip whole frame */
> >    		if (chan->qh->do_split &&
> According urb description in usb.h urb->actual_length used for non-iso
> transfers:
>
> "@actual_length: This is read in non-iso completion functions, and ...
>
>    * ISO transfer status is reported in the status and actual_length fields
>    * of the iso_frame_desc array, ...."
Yes,  urb->actual_length is used for non-iso transfers.  And for ISO 
transfer,  the most
usb class drivers can only use iso frame status and actual_length to 
handle usb data,
like: kernel v4.4 drivers/media/usb/uvc/uvc_video.c

But the usb devio driver really need the urb actual_length in the 
processcompl() if
handle ISO transfer, just as I mentioned in the commit message.

And I also found the same issue on raspberrypi board:
https://github.com/raspberrypi/linux/issues/903

So do you think we need to fix the usb devio driver, rather than fix dwc2?
I think maybe we can use urb actual length for ISO transfer, it seems that
don't cause any side-effect.

> Thanks,
> Minas

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