On Fri, Jul 08 2016, Felipe Balbi wrote: > My take on this is that it's calling max_t() to try and align to > wMaxPacketSize. We can see from original commit what was the intent: > > commit 03d27ade4941076b34c823d63d91dc895731a595 > Author: Felipe F. Tonello <e...@felipetonello.com> > Date: Wed Mar 9 19:39:30 2016 +0000 > > usb: gadget: f_midi: Fixed a bug when buflen was smaller than > wMaxPacketSize > > buflen by default (256) is smaller than wMaxPacketSize (512) in high-speed > devices. > > That caused the OUT endpoint to freeze if the host send any data packet of > length greater than 256 bytes. > > This is an example dump of what happended on that enpoint: > HOST: [DATA][Length=260][...] > DEVICE: [NAK] > HOST: [PING] > DEVICE: [NAK] > HOST: [PING] > DEVICE: [NAK] > ... > HOST: [PING] > DEVICE: [NAK] > > This patch fixes this problem by setting the minimum usb_request's buffer > size > for the OUT endpoint as its wMaxPacketSize. > > Acked-by: Michal Nazarewicz <min...@mina86.com> > Signed-off-by: Felipe F. Tonello <e...@felipetonello.com> > Signed-off-by: Felipe Balbi <felipe.ba...@linux.intel.com> > > diff --git a/drivers/usb/gadget/function/f_midi.c > b/drivers/usb/gadget/function/f_midi.c > index 56e2dde99b03..9ad51dcab982 100644 > --- a/drivers/usb/gadget/function/f_midi.c > +++ b/drivers/usb/gadget/function/f_midi.c > @@ -360,7 +360,9 @@ static int f_midi_set_alt(struct usb_function *f, > unsigned intf, unsigned alt) > /* allocate a bunch of read buffers and queue them all at once. */ > for (i = 0; i < midi->qlen && err == 0; i++) { > struct usb_request *req = > - midi_alloc_ep_req(midi->out_ep, midi->buflen); > + midi_alloc_ep_req(midi->out_ep, > + max_t(unsigned, midi->buflen, > + bulk_out_desc.wMaxPacketSize)); > if (req == NULL) > return -ENOMEM; > > Seems to me usb_ep_align_maybe() would cover this case just as well. But > then, Felipe's UDC driver seems to need quirk_ep_out_aligned_size. Felipe?
In that case, I agree that max is likely unnecessary. -- Best regards ミハウ “𝓶𝓲𝓷𝓪86” ナザレヴイツ «If at first you don’t succeed, give up skydiving» -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html