On Fri, Jul 03, 2015 at 10:03:22AM -0400, Alan Stern wrote:
> On Fri, 3 Jul 2015, Peter Chen wrote:
>
> > According to the USB 2.0 Spec CH5.5.3 and CH8.5.3.2, only control
> > read (IN) needs zero length packet.
> >
> > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx>
> > ---
> > drivers/usb/gadget/composite.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> > index 1c0c3da..c3898b5 100644
> > --- a/drivers/usb/gadget/composite.c
> > +++ b/drivers/usb/gadget/composite.c
> > @@ -1744,7 +1744,8 @@ unknown:
> > }
> > req->length = value;
> > req->context = cdev;
> > - req->zero = value < w_length;
> > + if (ctrl->bRequestType == USB_DIR_IN)
> > + req->zero = value < w_length;
> > value = composite_ep0_queue(cdev, req, GFP_ATOMIC);
> > if (value < 0) {
> > DBG(cdev, "ep_queue --> %d\n", value);
> > @@ -1820,7 +1821,8 @@ try_fun_setup:
> > if (value >= 0 && value != USB_GADGET_DELAYED_STATUS) {
> > req->length = value;
> > req->context = cdev;
> > - req->zero = value < w_length;
> > + if (ctrl->bRequestType == USB_DIR_IN)
> > + req->zero = value < w_length;
> > value = composite_ep0_queue(cdev, req, GFP_ATOMIC);
> > if (value < 0) {
> > DBG(cdev, "ep_queue --> %d\n", value);
>
> This change is not needed. A UDC driver is always supposed to ignore
> req->zero for OUT transfers. (It also is supposed to ignore req->zero
> if req->length == 0 or req->length % maxpacket != 0.)
>
This can avoid every UDC driver doing it, the UDC driver can consider
the zero flag is only set at OUT transfer.
--
Best Regards,
Peter Chen
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