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

[Felipe Balbi <balbi@ti.com>]

On Thu, Aug 21, 2014 at 10:00:46AM +0200, Lukasz Majewski wrote:
> 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.

you will need to poll anyways for a bunch of other things. There are
some details in DWC3 which are mandated that you wait for event X before
doing Y. For example control transfers, it's mandatory that you wait for
a XferNotReady event before trying to start a Status Phase.

> > > > 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.

right, once USB-IF does that, I hope they switch to bulk endpoints :-p

-- 
balbi
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