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Date:   Tue, 10 Nov 2020 12:39:38 +0100
From:   "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To:     Peter Chen <peter.chen@nxp.com>
Cc:     Pawel Laszczak <pawell@cadence.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "balbi@kernel.org" <balbi@kernel.org>,
        "colin.king@canonical.com" <colin.king@canonical.com>,
        "rogerq@ti.com" <rogerq@ti.com>, Rahul Kumar <kurahul@cadence.com>,
        "nsekhar@ti.com" <nsekhar@ti.com>
Subject: Re: [PATCH v2 03/10] usb: cdns3: Moves reusable code to separate
 module
Message-ID: <X6p7+nXa/H4uqj0+@kroah.com>
References: <20201106114300.1245-1-pawell@cadence.com>
 <20201106114300.1245-4-pawell@cadence.com>
 <20201110090854.GB22481@b29397-desktop>
 <DM6PR07MB55294E87F6D76BA3C04E510ADDE90@DM6PR07MB5529.namprd07.prod.outlook.com>
 <20201110112054.GC22481@b29397-desktop>
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In-Reply-To: <20201110112054.GC22481@b29397-desktop>
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On Tue, Nov 10, 2020 at 11:21:22AM +0000, Peter Chen wrote:
> On 20-11-10 09:20:54, Pawel Laszczak wrote:
> > Hi,
> > 
> > >>
> > >>  int cdns3_hw_role_switch(struct cdns3 *cdns);
> > >> -int cdns3_init(struct cdns3 *cdns);
> > >> -int cdns3_remove(struct cdns3 *cdns);
> > >> +extern int cdns3_init(struct cdns3 *cdns);
> > >> +extern int cdns3_remove(struct cdns3 *cdns);
> > >
> > >Why add "extern" here and below?
> > >
> > 
> > These functions are the API between cdnsp and cdns3 modules.
> > It's looks like a common approach in kernel.
> > Many or even most of API function in kernel has "extern". 
> > 
> 
> Even you have not written "extern" keyword, the "extern" is
> added implicitly by compiler. Usually, we use "extern" for variable
> or the function is defined at assembly. You could see some
> "extern" keyword use cases at include/linux/device.h.

We are moving away from using this keyword for functions now, if at all
possible please.  Only use it for variables, I think checkpatch now
catches it as well.

thanks,

greg k-h