linux-kernel - Re: [PATCH] usb: udc: add gadget state kobject uevent

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Date:	Mon, 22 Jul 2013 12:28:54 +0300
From:	Felipe Balbi <balbi@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Felipe Balbi <balbi@...com>, Rong Wang <wr011235813@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Rong.Wang@....com>
Subject: Re: [PATCH] usb: udc: add gadget state kobject uevent

Hi,

On Thu, Jul 18, 2013 at 09:50:37AM -0400, Alan Stern wrote:
> On Thu, 18 Jul 2013, Felipe Balbi wrote:
> 
> > > > yes. Only the UDC driver knows when the controller is moving among those
> > > > states.
> > > 
> > > Not quite.  Only the gadget driver knows when the transition between 
> > > ADDRESS and CONFIGURED occurs.  This should be added to composite.c.
> > 
> > that's not entirely true :-) See how we handle that in dwc3:
> > 
> > | static int dwc3_ep0_set_config(struct dwc3 *dwc, struct usb_ctrlrequest *ctrl)
> > | {
> > | 	enum usb_device_state state = dwc->gadget.state;
> > | 	u32 cfg;
> > | 	int ret;
> > | 	u32 reg;
> > | 
> > | 	dwc->start_config_issued = false;
> > | 	cfg = le16_to_cpu(ctrl->wValue);
> > | 
> > | 	switch (state) {
> > | 	case USB_STATE_DEFAULT:
> > | 		return -EINVAL;
> > | 		break;
> > | 
> > | 	case USB_STATE_ADDRESS:
> > | 		ret = dwc3_ep0_delegate_req(dwc, ctrl);
> > | 		/* if the cfg matches and the cfg is non zero */
> > | 		if (cfg && (!ret || (ret == USB_GADGET_DELAYED_STATUS))) {
> > | 			usb_gadget_set_state(&dwc->gadget,
> > | 					USB_STATE_CONFIGURED);
> 
> In theory, this should not occur until the gadget driver has finished 
> the transition to the CONFIGURED state, which doesn't occur until later 
> in the case of USB_GADGET_DELAYED_STATUS.
> 
> > | 
> > | 			/*
> > | 			 * Enable transition to U1/U2 state when
> > | 			 * nothing is pending from application.
> > | 			 */
> > | 			reg = dwc3_readl(dwc->regs, DWC3_DCTL);
> > | 			reg |= (DWC3_DCTL_ACCEPTU1ENA | DWC3_DCTL_ACCEPTU2ENA);
> > | 			dwc3_writel(dwc->regs, DWC3_DCTL, reg);
> > | 
> > | 			dwc->resize_fifos = true;
> > | 			dev_dbg(dwc->dev, "resize fifos flag SET\n");
> > | 		}
> > | 		break;
> > | 
> > | 	case USB_STATE_CONFIGURED:
> > | 		ret = dwc3_ep0_delegate_req(dwc, ctrl);
> > | 		if (!cfg)
> > | 			usb_gadget_set_state(&dwc->gadget,
> > | 					USB_STATE_ADDRESS);
> 
> No check on the value of ret?  What if the request was rejected?
> 
> > | 		break;
> > | 	default:
> > | 		ret = -EINVAL;
> > | 	}
> > | 	return ret;
> > | }
> 
> This illustrates the folly of exposing your code to public review.  :-)

it's always good to have extra eyes looking at the code, I'll patch
those up, but since it has always been like that and nobody complained,
I won't tag it for stable.

-- 
balbi

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