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

[Lukasz Majewski]

Hi Felipe,

> 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.

My point is that you will need to pool in u-boot to emulate this IRQ.

> 
> > > 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.

As you can see the standard is a bit old now... and should be revised.

> 
> > > 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.
> 

Ok.

-- 
Best regards,

Lukasz Majewski

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