linux-kernel - Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160520013931.GA10896@shlinux2>
Date:	Fri, 20 May 2016 09:39:31 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Roger Quadros <rogerq@...com>
Cc:	peter.chen@...escale.com, balbi@...nel.org, tony@...mide.com,
	gregkh@...uxfoundation.org, dan.j.williams@...el.com,
	mathias.nyman@...ux.intel.com, Joao.Pinto@...opsys.com,
	sergei.shtylyov@...entembedded.com, jun.li@...escale.com,
	grygorii.strashko@...com, yoshihiro.shimoda.uh@...esas.com,
	robh@...nel.org, nsekhar@...com, b-liu@...com,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

On Wed, May 18, 2016 at 03:45:11PM +0300, Roger Quadros wrote:
> On 18/05/16 06:18, Peter Chen wrote:
> > On Mon, May 16, 2016 at 12:51:53PM +0300, Roger Quadros wrote:
> >> On 16/05/16 12:23, Peter Chen wrote:
> >>> On Mon, May 16, 2016 at 11:26:57AM +0300, Roger Quadros wrote:
> >>>> Hi,
> >>>>
> >>>> On 16/05/16 10:02, Peter Chen wrote:
> >>>>> On Fri, May 13, 2016 at 01:03:27PM +0300, Roger Quadros wrote:
> >>>>>> +
> >>>>>> +static int usb_gadget_connect_control(struct usb_gadget *gadget, bool connect)
> >>>>>> +{
> >>>>>> +	struct usb_udc *udc;
> >>>>>> +
> >>>>>> +	mutex_lock(&udc_lock);
> >>>>>> +	udc = usb_gadget_to_udc(gadget);
> >>>>>> +	if (!udc) {
> >>>>>> +		dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
> >>>>>> +			__func__);
> >>>>>> +		mutex_unlock(&udc_lock);
> >>>>>> +		return -EINVAL;
> >>>>>> +	}
> >>>>>> +
> >>>>>> +	if (connect) {
> >>>>>> +		if (!gadget->connected)
> >>>>>> +			usb_gadget_connect(udc->gadget);
> >>>>>> +	} else {
> >>>>>> +		if (gadget->connected) {
> >>>>>> +			usb_gadget_disconnect(udc->gadget);
> >>>>>> +			udc->driver->disconnect(udc->gadget);
> >>>>>> +		}
> >>>>>> +	}
> >>>>>> +
> >>>>>> +	mutex_unlock(&udc_lock);
> >>>>>> +
> >>>>>> +	return 0;
> >>>>>> +}
> >>>>>> +
> >>>>>
> >>>>> Since this is called for vbus interrupt, why not using
> >>>>> usb_udc_vbus_handler directly, and call udc->driver->disconnect
> >>>>> at usb_gadget_stop.
> >>>>
> >>>> We can't assume that this is always called for vbus interrupt so
> >>>> I decided not to call usb_udc_vbus_handler.
> >>>>
> >>>> udc->vbus is really pointless for us. We keep vbus states in our
> >>>> state machine and leave udc->vbus as ture always.
> >>>>
> >>>> Why do you want to move udc->driver->disconnect() to stop?
> >>>> If USB controller disconnected from bus then the gadget driver
> >>>> must be notified about the disconnect immediately. The controller
> >>>> may or may not be stopped by the core.
> >>>>
> >>>
> >>> Then, would you give some comments when this API will be used?
> >>> I was assumed it is only used for drd state machine.
> >>
> >> drd_state machine didn't even need this API in the first place :).
> >> You guys wanted me to separate out start/stop and connect/disconnect for full OTG case.
> >> Won't full OTG state machine want to use this API? If not what would it use?
> >>
> > 
> > Oh, I meant only drd and fully otg state machine needs it. I am
> > wondering if we need have a new API to do it. Two questions:
> 
> OK.
> > 
> > - Except for vbus interrupt, any chances this API will be used at
> > current logic?
> 
> I don't think so. But we can't assume caller behaviour for any API.
> 
> > - When this API is called but without a coming gadget->stop?
> > 
> Never for DRD case. But we want to catch wrong users.
> 

In future, otg_start_gadget will be used for both DRD and fully OTG FSM.
There is no otg_loc_conn at current DRD FSM, but there is
otg_loc_conn at current OTG FSM, see below.

DRD FSM:
	case OTG_STATE_B_IDLE:
		drd_set_protocol(fsm, PROTO_UNDEF);
		otg_drv_vbus(otg, 0);
		break;
	case OTG_STATE_B_PERIPHERAL:
		drd_set_protocol(fsm, PROTO_GADGET);
		otg_drv_vbus(otg, 0);
		break;

OTG FSM:
	case OTG_STATE_B_IDLE:
		otg_drv_vbus(otg, 0);
		otg_chrg_vbus(otg, 0);
		otg_loc_conn(otg, 0);
		otg_loc_sof(otg, 0);
		/*
		 * Driver is responsible for starting ADP probing
		 * if ADP sensing times out.
		 */
		otg_start_adp_sns(otg);
		otg_set_protocol(fsm, PROTO_UNDEF);
		otg_add_timer(otg, B_SE0_SRP);
		break;
	case OTG_STATE_B_PERIPHERAL:
		otg_chrg_vbus(otg, 0);
		otg_loc_sof(otg, 0);
		otg_set_protocol(fsm, PROTO_GADGET);
		otg_loc_conn(otg, 1);
		break;

My original suggestion is to have an API to do pull dp and this API
will be used at both DRD and OTG FSM, and called at otg_loc_conn.
The (de)initialize is the same for both two FSMs, it both includes
init peripheral mode and pull up dp, and can be done by drd_set_protocol(fsm, PROTO_GADGET)
otg_loc_conn(otg, 1);

What do you think?

-- 

Best Regards,
Peter Chen