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SubjectRe: [PATCH] usb: dwc2: host: fix isoc urb actual length
On Mon, 6 Nov 2017, wlf wrote:

> Hi Minas,
>
> 在 2017年11月06日 17:28, Minas Harutyunyan 写道:
> > 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 camera,
> >> 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@rock-chips.com>
> >> ---
> >> 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;
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