From: Peter Chen <Peter.Chen@freescale.com>
To: Baolin Wang <baolin.wang@linaro.org>
CC: Felipe Balbi <balbi@ti.com>, Mark Brown <broonie@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "sojka@merica.cz" <sojka@merica.cz>,
        Alan Stern <stern@rowland.harvard.edu>,
        "andreas@gaisler.com" <andreas@gaisler.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: [PATCH 2/2] gadget: Support for the usb charger framework
Thread-Topic: [PATCH 2/2] gadget: Support for the usb charger framework
Thread-Index: AQHQ0BaxZP3OMS4IlUyXJ34Mbmgr1J4AjpUA//+sWoCAAAPD8A==
Date: Fri, 7 Aug 2015 09:07:09 +0000
Message-ID: <BN3PR0301MB0849D0FD8755EF5F23DB44B281730@BN3PR0301MB0849.namprd03.prod.outlook.com>
References: <cover.1438844453.git.baolin.wang@linaro.org>
	<8fcb9ff7a8e01bec53813f0702ff606bf4982943.1438844454.git.baolin.wang@linaro.org>
	<20150807054554.GE13200@shlinux2>
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> >>  /**
> >>   * 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
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