On Mon, 6 Jul 2015, Peter Chen wrote:
> 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.
But this patch affects only control transfers, not bulk transfers.
And it doesn't handle the cases where req->length == 0 or req->length %
maxpacket != 0.
Alan Stern
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