[U-Boot] [UBOOT RFC PATCH 07/13] usb: gadget: g_dnl: Explicitly set the max packet size in descriptor

Felipe Balbi
2014-08-20T16:11:13Z

On Wed, Aug 20, 2014 at 09:34:13AM +0200, Lukasz Majewski wrote:
> Hi Felipe,
>
> > On Tue, Aug 19, 2014 at 09:08:00PM +0530, Kishon Vijay Abraham I
> > wrote:
> > >
> > >
> > > On Monday 18 August 2014 08:26 PM, Lukasz Majewski wrote:
> > > > Hi Kishon,
> > > >
> > > >>> Explicity set the max packet size in the device descriptor to
> > > >>> 0x40 as specified in the device class specification for device
> > > >>> firmware upgrade. Also changed debug to printf to explicitly
> > > >>> notify the user if the device has been enumerated.
> > > >
> > > > It seems like this patch slipped without my attention ...
> > > >
> > > > Hence, I'd like to ask why you must hardcode the packet size here?
> > >
> > > http://www.usb.org/developers/devclass_docs/usbdfu10.pdf (in
> > > section 4.2.1 DFU Mode Device Descriptor), specifies the
> > > bMaxPacketSize0 can be 8,16,32,64. And the value we get from
> > > gadget is 512. So hard coded it.
> >
> > as I mentioned, this should be changed on connection done interrupt.
>
> In the u-boot it is set up during binding the composite.

look at dwc3. dwc3 has a connection done IRQ which also tells me the
negotiated link speed.

> > DFU has one of the poorest documentations for a USB Class and has some
> > moronic definitions.
>
> Frankly speaking I prefer to have the worst standard than some
> "brilliant" in house developed protocols.

nobody is talking about changing the protocol. DFU was written back when
Full speed was the fastest USB on earth.

> > What happens if you want ot run DFU with a
> > superspeed controller (such as dwc3) when connected to a superspeed
> > port. We cannot use ep0 packet size as 64, right ?
>
> Correct me if I'm wrong, but MaxPacket for SS ep0 is 2^9 = 512B.
> I'm curious if dfu-util will manage to handle ep0 MaxPacket size up to
> 512B.
> It not, then we shall be able to fallback to 64B.

should be a test away.

--
balbi
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