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

[Alan Stern]

On Mon, 6 Nov 2017, wlf wrote:

> 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.

That sounds like a good idea.  Minas, does the following patch fix your 
problem?

In theory we could do this calculation for every isochronous URB, not 
just those coming from usbfs.  But I don't think there's any point, 
since the USB class drivers don't use it.

Alan Stern



Index: usb-4.x/drivers/usb/core/devio.c
===================================================================
--- usb-4.x.orig/drivers/usb/core/devio.c
+++ usb-4.x/drivers/usb/core/devio.c
@@ -1828,6 +1828,18 @@ static int proc_unlinkurb(struct usb_dev
 	return 0;
 }
 
+static void compute_isochronous_actual_length(struct urb *urb)
+{
+	unsigned i;
+
+	if (urb->number_of_packets > 0) {
+		urb->actual_length = 0;
+		for (i = 0; i < urb->number_of_packets; i++)
+			urb->actual_length +=
+					urb->iso_frame_desc[i].actual_length;
+	}
+}
+
 static int processcompl(struct async *as, void __user * __user *arg)
 {
 	struct urb *urb = as->urb;
@@ -1835,6 +1847,8 @@ static int processcompl(struct async *as
 	void __user *addr = as->userurb;
 	unsigned int i;
 
+	compute_isochronous_actual_length(urb);
+
 	if (as->userbuffer && urb->actual_length) {
 		if (copy_urb_data_to_user(as->userbuffer, urb))
 			goto err_out;
@@ -2003,6 +2017,8 @@ static int processcompl_compat(struct as
 	void __user *addr = as->userurb;
 	unsigned int i;
 
+	compute_isochronous_actual_length(urb);
+
 	if (as->userbuffer && urb->actual_length) {
 		if (copy_urb_data_to_user(as->userbuffer, urb))
 			return -EFAULT;