Hi, On Mon, Jul 18, 2011 at 12:38:03PM +0200, Sebastian Andrzej Siewior wrote: > Tanya Brokhman wrote: > >Hi Sebastian, > Hi Tanya, > > >>For bMaxPacketSize0 we usually take what is specified in ep0- > >>>maxpacket. > >>This is fine in most cases, however on SuperSpeed bMaxPacketSize0 > >>specifies the exponent instead of the actual size in bytes. The only > >>valid value on SS is 9 which denotes 512 bytes. > >> > > > >You're right but something in this patch still bothers me: according to your > >patch it is possible that cdev->gadget->ep0->maxpacket (that is set by the > >DCD) won't match the bMaxPacketSize0 we report to the host in the device > >descriptor. > >cdev->gadget->ep0->maxpacket should be determined by the DCD otherwise it > >won't function correctly. So, you're right that it should be 9 for SS but it > >seems to me that it should be the DCDs responsibility to set the correct > >value. > >In the current code the device descriptor is updated according to the value > >of bMaxPacketSize0 set by the DCD: > > > > cdev->desc.bMaxPacketSize0 = cdev->gadget->ep0->maxpacket; > > > >I think this should remain as is. For If the DCD declared that it supports > >SS but neglected to set cdev->gadget->ep0->maxpacket to the correct value it > >doesn't seem right to me to update the device descriptor. > >I would add a warning message (or even ERROR) if the speed is SS but > >cdev->gadget->ep0->maxpacket != 9. > > I've been thinking about this and decided against it: > maxpacket size is u16 and used in various for comparison for instance in > the choose_ep code. It can be even 1024 on bulk SS eps. So if we change > the meaning of the field from bytes to exponent than it makes the code > more complicated as it has to check speed each time. moreover ep*->maxpacket is a copy of wMaxPacketSize, not bMaxPacketSize0 ;-) wMaxPacketSize is 512 for SS ep0. -- balbi
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