Re: [PATCH v2 1/5] usb: gadget: Add remote wakeup capable flag

[Thinh Nguyen]

On Fri, Jan 20, 2023, Alan Stern wrote:
> On Sat, Jan 21, 2023 at 02:02:36AM +0000, Thinh Nguyen wrote:
> > On Fri, Jan 20, 2023, Alan Stern wrote:
> > > A UDC design might have multiple versions, some supporting remote wakeup 
> > > and others not.  But drivers generally use a single static 
> > > usb_gadget_ops structure, and they don't modify it at runtime to account 
> > > for hardware differences.  So if a single driver controls those multiple 
> > > versions, you can't rely on the presence of gadget->ops->wakeup to 
> > > indicate whether there actually is hardware remote wakeup support.
> > > 
> > > Ideally, the usb_gadget structure should have a wakeup_capable flag 
> > > which the UDC driver would set appropriately (probably during its probe 
> > > routine).
> > > 
> > 
> > I was thinking that it can be handled by the
> > usb_gadget_enable_remote_wakeup() so we can do away with the
> > wakeup_capable flag.
> 
> usb_gadget_enable_remote_wakeup() gets called when the gadget or 
> function is suspended, right?  But a gadget driver may want to know long 
> before that whether the UDC supports remote wakeup, in order to set up 
> its config descriptor correctly.
> 

No, this is to be called during set configuration. If the configuration
doesn't support remote wakeup, the device should not be able to send
remote wakeup.

BR,
Thinh