linux-kernel - RE: [PATCH 4/8] vfio/mdev: Drop redundant extern for exported symbols

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Date:   Mon, 25 Mar 2019 21:27:16 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 4/8] vfio/mdev: Drop redundant extern for exported symbols



> -----Original Message-----
> From: Alex Williamson <alex.williamson@...hat.com>
> Sent: Monday, March 25, 2019 2:50 PM
> To: Kirti Wankhede <kwankhede@...dia.com>
> Cc: Parav Pandit <parav@...lanox.com>; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH 4/8] vfio/mdev: Drop redundant extern for exported
> symbols
> 
> On Tue, 26 Mar 2019 00:37:04 +0530
> Kirti Wankhede <kwankhede@...dia.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@...lanox.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@...il.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,
> 
We always improve the kernel, sometimes in pieces, sometime at subsystem level or sometimes tree wide.
This is done mdev level.
device core is not good example to point that they use 'extern' so its fine here...
That was written more than 10 years ago.
So we should be open to improvements.. silly or large..