Re: [PATCH v4 1/4] cmd: bind: Add unbind command with driver filter

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Tom,

> > > >>>>> Cannot find a device with path /ocp/usb@47400000/usb@47401000    
> > > >>>>> => unbind /ocp/usb@47400000/usb@47401000
> > > >>>>> => dm tree    
> > > >>>>>     misc          0  [ + ]   ti-musb-wrapper       |   |-- usb@47400000
> > > >>>>>     usb           0  [   ]   ti-musb-host          |   |   `-- usb@47401800    
> > > >>>>> => fastboot usb 0
> > > >>>>> => bind /ocp/usb@47400000/usb@47401000 ti-musb-peripheral
> > > >>>>> => dm tree    
> > > >>>>>     misc          0  [ + ]   ti-musb-wrapper       |   |-- usb@47400000
> > > >>>>>     usb           0  [   ]   ti-musb-host          |   |   |-- usb@47401800
> > > >>>>>     usb           0  [   ]   ti-musb-peripheral    |   |   `-- usb@47401000    
> > > >>>>> => fastboot usb 0    
> > > >>>>> musb-hdrc: peripheral reset irq lost!
> > > >>>>> # works! (the irq-related line above as always been there)
> > > >>>>>
> > > >>>>> So now, how do we make this process easy/understandable?    
> > > >>>>
> > > >>>> What would be your proposal ?    
> > > > 
> > > > At least I would appreciate:
> > > > - to select CMD_BIND "by default" when relevant
> > > > - to make the fastboot error more readable for the regular user    
> > > 
> > > Since with this 'unbind ethernet 0' this is orthogonal to this series, send separate patches, thanks.  
> > 
> > This is not orthogonal, I am sorry.
> > 
> > version X:
> > - tftp works "out of the box"
> > - fastboot works "out of the box"
> > version X+1:
> > - tftp works "out of the box"
> > - fastboot returns an obscure error
> > 
> > 1/ If we now *need* the bind/unbind commands, the series must take care
> >    of it.
> > 2/ Without proper error message you just break fastboot for most
> >    regular users (basically everyone but few U-Boot devs).  
> 
> You're missing the class of users that will be impacted here.  In order
> for there to be a change here, you have to already be in the case where
> you have CONFIG_USB_ETHER=y and gadget ethernet device isn't just
> enabled but also initialized by default by calling usb_ether_init().
> That's a very small list.  It's basically am33xx, two mediatek reference
> platforms and xilinx_zynqmp_virt.  Given that am33xx defconfigs also
> setup DFU, I'm not really sure just how many people use gadget ethernet.
> The normal flow on modern devices is to be calling bind/unbind here
> already.

Can we make this behavior explicit to the user? I am sorry, maybe it is
the normal flow for you, but I am a regular U-Boot user and I totally
missed that requirement.

Typical situation: one needs to use <whatever-gadget> but none is bound
to the UDC (or another is bound), could we make the error messages more
explicit if we decide not to unbind/bind the right one automatically
because it is too "costly"?

Thanks,
Miquèl