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Date:   Mon, 25 Mar 2019 13:49:50 -0600
From:   Alex Williamson <alex.williamson@redhat.com>
To:     Kirti Wankhede <kwankhede@nvidia.com>
Cc:     Parav Pandit <parav@mellanox.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/8] vfio/mdev: Drop redundant extern for exported
 symbols
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On Tue, 26 Mar 2019 00:37:04 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 3/23/2019 4:50 AM, Parav Pandit wrote:
> > There is no need use 'extern' for exported functions.
> > 
> > Signed-off-by: Parav Pandit <parav@mellanox.com>
> > ---
> >  include/linux/mdev.h | 21 ++++++++++-----------
> >  1 file changed, 10 insertions(+), 11 deletions(-)
> > 
> > diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> > index b6e048e..0924c48 100644
> > --- a/include/linux/mdev.h
> > +++ b/include/linux/mdev.h
> > @@ -118,21 +118,20 @@ struct mdev_driver {
> >  
> >  #define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
> >  
> > -extern void *mdev_get_drvdata(struct mdev_device *mdev);
> > -extern void mdev_set_drvdata(struct mdev_device *mdev, void *data);
> > -extern uuid_le mdev_uuid(struct mdev_device *mdev);
> > +void *mdev_get_drvdata(struct mdev_device *mdev);
> > +void mdev_set_drvdata(struct mdev_device *mdev, void *data);
> > +uuid_le mdev_uuid(struct mdev_device *mdev);
> >  
> >  extern struct bus_type mdev_bus_type;
> >  
> > -extern int  mdev_register_device(struct device *dev,
> > -				 const struct mdev_parent_ops *ops);
> > -extern void mdev_unregister_device(struct device *dev);
> > +int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops);
> > +void mdev_unregister_device(struct device *dev);
> >  
> > -extern int  mdev_register_driver(struct mdev_driver *drv, struct module *owner);
> > -extern void mdev_unregister_driver(struct mdev_driver *drv);
> > +int mdev_register_driver(struct mdev_driver *drv, struct module *owner);
> > +void mdev_unregister_driver(struct mdev_driver *drv);
> >  
> > -extern struct device *mdev_parent_dev(struct mdev_device *mdev);
> > -extern struct device *mdev_dev(struct mdev_device *mdev);
> > -extern struct mdev_device *mdev_from_dev(struct device *dev);
> > +struct device *mdev_parent_dev(struct mdev_device *mdev);
> > +struct device *mdev_dev(struct mdev_device *mdev);
> > +struct mdev_device *mdev_from_dev(struct device *dev);
> >  
> >  #endif /* MDEV_H */
> >   
> 
> Adding 'extern' to exported symbols is inline to other exported
> functions from device's core module like device_register(),
> device_unregister(), get_device(), put_device()

Right, I'd be inclined to leave this as a style choice, but...

commit 3fe5dbfef47e992b810cbe82af1df02d8255fb8c
Author: Alexey Dobriyan <adobriyan@gmail.com>
Date:   Thu Jan 3 15:26:16 2019 -0800

    Documentation/process/coding-style.rst: don't use "extern" with function prototypes
    
    `extern' with function prototypes makes lines longer and creates more
    characters on the screen.
    
    Do not bug people with checkpatch.pl warnings for now as fallout can be
    devastating.

So it's a new decision and rather weakly imposed new standard.  Thanks,

Alex