linux-kernel - Re: [PATCH v6 07/12] usb: otg: add OTG/dual-role core

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Date:	Tue, 26 Apr 2016 14:28:09 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Jun Li <jun.li@....com>
Cc:	Roger Quadros <rogerq@...com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"abrestic@...omium.org" <abrestic@...omium.org>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v6 07/12] usb: otg: add OTG/dual-role core

On Tue, Apr 26, 2016 at 05:11:36AM +0000, Jun Li wrote:
> Hi
> 
> > -----Original Message-----
> > From: Peter Chen [mailto:hzpeterchen@...il.com]
> > Sent: Tuesday, April 26, 2016 11:47 AM
> > To: Jun Li <jun.li@....com>
> > Cc: Roger Quadros <rogerq@...com>; stern@...land.harvard.edu;
> > balbi@...nel.org; gregkh@...uxfoundation.org; peter.chen@...escale.com;
> > dan.j.williams@...el.com; jun.li@...escale.com;
> > mathias.nyman@...ux.intel.com; tony@...mide.com; Joao.Pinto@...opsys.com;
> > abrestic@...omium.org; r.baldyga@...sung.com; linux-usb@...r.kernel.org;
> > linux-kernel@...r.kernel.org; linux-omap@...r.kernel.org
> > Subject: Re: [PATCH v6 07/12] usb: otg: add OTG/dual-role core
> > 
> > On Tue, Apr 26, 2016 at 02:07:56AM +0000, Jun Li wrote:
> > > > +struct usb_otg *usb_otg_register(struct device *dev,
> > > > +				 struct usb_otg_config *config) {
> > > > +	struct usb_otg *otg;
> > > > +	struct otg_wait_data *wait;
> > > > +	int ret = 0;
> > > > +
> > > > +	if (!dev || !config || !config->fsm_ops)
> > > > +		return ERR_PTR(-EINVAL);
> > > > +
> > > > +	/* already in list? */
> > > > +	mutex_lock(&otg_list_mutex);
> > > > +	if (usb_otg_get_data(dev)) {
> > > > +		dev_err(dev, "otg: %s: device already in otg list\n",
> > > > +			__func__);
> > > > +		ret = -EINVAL;
> > > > +		goto unlock;
> > > > +	}
> > > > +
> > > > +	/* allocate and add to list */
> > > > +	otg = kzalloc(sizeof(*otg), GFP_KERNEL);
> > > > +	if (!otg) {
> > > > +		ret = -ENOMEM;
> > > > +		goto unlock;
> > > > +	}
> > > > +
> > > > +	otg->dev = dev;
> > > > +	otg->caps = config->otg_caps;
> > > > +
> > > > +	if ((otg->caps->hnp_support || otg->caps->srp_support ||
> > > > +	     otg->caps->adp_support) && !config->otg_work)
> > > > +		dev_info(dev, "otg: limiting to dual-role\n");
> > >
> > > dev_err, this should be an error.
> > 
> > The condition may be wrong, but it is an information to show that current
> > OTG is dual-role.
> 
> This should not happen in any correct design, I even doubt if we
> should try to continue by "downgrade" it to be duel role, currently
> the only example user is dual role, so doing like this can't be
> tested by real case, this downgrade is not so easy like we image,
> at least for chipidea otg driver, simply replace a queue worker may
> not work, as we have much more difference between the 2 configs.
> 

Would you show more why chipidea can't work just replace the work item,
and see if anything we still can improve for this framework?

-- 
Best Regards,
Peter Chen