Re: [PATCH] usb: chipidea: reuse the platform_data to store the ci info

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On Fri, Aug 14, 2015 at 10:26:35AM -0400, Alan Stern wrote:
> On Fri, 14 Aug 2015, Peter Chen wrote:
> 
> > > In the old days, a single device could be a USB host controller and
> > > nothing else.  Then later, a single device could be either a host
> > > controller or a device controller.  Now a single device can be both.
> > > 
> > > Obviously this causes problems for our original design, where the 
> > > device's drvdata stored a pointer to the hcd structure or the udc 
> > > structure.
> > > 
> > > In principle, the drvdata should point to something that contains
> > > pointers to both the hcd and udc structures.  Maybe also an otg
> > > structure.  That would require a lot of changes to existing code but it
> > > might be worthwhile.
> > > 
> > 
> > Yes, the core device drvdata should contain standard hcd, gadget,
> > otg structure together. Currently, the gadget is child device
> > for core device, it is reasonable the same for hcd, and we can
> > create device for chipidea host to achieve it. The dwc3 driver
> > does the similar things.
> > 
> > Below is the reference device hierarchy for current IP driver:
> > 
> > 		Glue Layer Device
> > 		       |
> > 		       |
> > 		       |
> > 		 IP  Core Device
> > 		   	|    
> > 		   |----|----|
> > 		   |	|    |
> > 		Gadget	hcd  otg
> > 
> > Alan/Felipe, what do you think?
> 
> That's not quite what I had in mind.  I was thinking of something more 
> like this:
> 
> 		Platform device ---- drvdata ----> struct usb_pointers
> 			|
> 			|
> 		|-------|-------|
> 		|	|	|
> 	      gadget   hcd     otg
> 
> where struct usb_pointers (maybe you can think of a better name) looks 
> like this:
> 
> struct usb_pointers {
> 	struct usb_hcd		*hcd;
> 	struct usb_gadget	*gadget;
> 	struct usb_otg		*otg;
> };
> 
> If you want, you can use your IP Core device in place of my platform
> device.  All that matters is that the parent device of the root hub
> (for hosts) or gadget (for peripherals) should store the address of a 
> usb_pointers structure in its drvdata.

that looks pretty clean to me, Alan. Wonder how that looks after
actually implementing it.

-- 
balbi

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