linux-kernel - RE: [PATCH 2/2] gadget: Support for the usb charger framework

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Message-ID: <BN3PR0301MB0849D0FD8755EF5F23DB44B281730@BN3PR0301MB0849.namprd03.prod.outlook.com>
Date:	Fri, 7 Aug 2015 09:07:09 +0000
From:	Peter Chen <Peter.Chen@...escale.com>
To:	Baolin Wang <baolin.wang@...aro.org>
CC:	Felipe Balbi <balbi@...com>, Mark Brown <broonie@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"sojka@...ica.cz" <sojka@...ica.cz>,
	Alan Stern <stern@...land.harvard.edu>,
	"andreas@...sler.com" <andreas@...sler.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH 2/2] gadget: Support for the usb charger framework

 
> >>  /**
> >>   * struct usb_udc - describes one usb device controller @@ -127,12
> >> +128,45 @@ void usb_gadget_giveback_request(struct usb_ep *ep,  }
> >> EXPORT_SYMBOL_GPL(usb_gadget_giveback_request);
> >>
> >> +int usb_gadget_register_notify(struct usb_gadget *gadget,
> >> +                            struct notifier_block *nb) {
> >> +     unsigned long flags;
> >> +     int ret;
> >> +
> >> +     spin_lock_irqsave(&gadget->lock, flags);
> >
> > I find you use so many spin_lock_irqsave, any reasons for that?
> > Why mutex_lock can't be used?
> >
> 
> The spin_lock_irqsave() can make it as a atomic notifier, that can make sure the
> gadget state event can be quickly reported to the user who register a notifier
> on the gadget device. Is it OK?
> 

I don't think it is a good reason, spin_lock_irqsave is usually used for protecting
data which is accessed at atomic environment. 

Peter