linux-kernel - Re: [PATCH v3 04/27] ocxl: Remove unnecessary externs

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Date:   Wed, 26 Feb 2020 22:54:37 +0800
From:   'Baoquan He' <bhe@...hat.com>
To:     Greg Kurz <groug@...d.org>
Cc:     Alastair D'Silva <alastair@...ilva.org>,
        'Alastair D'Silva' <alastair@....ibm.com>,
        "'Aneesh Kumar K . V'" <aneesh.kumar@...ux.ibm.com>,
        'Oliver O'Halloran' <oohall@...il.com>,
        'Benjamin Herrenschmidt' <benh@...nel.crashing.org>,
        'Paul Mackerras' <paulus@...ba.org>,
        'Michael Ellerman' <mpe@...erman.id.au>,
        'Frederic Barrat' <fbarrat@...ux.ibm.com>,
        'Andrew Donnellan' <ajd@...ux.ibm.com>,
        'Arnd Bergmann' <arnd@...db.de>,
        'Greg Kroah-Hartman' <gregkh@...uxfoundation.org>,
        'Dan Williams' <dan.j.williams@...el.com>,
        'Vishal Verma' <vishal.l.verma@...el.com>,
        'Dave Jiang' <dave.jiang@...el.com>,
        'Ira Weiny' <ira.weiny@...el.com>,
        'Andrew Morton' <akpm@...ux-foundation.org>,
        'Mauro Carvalho Chehab' <mchehab+samsung@...nel.org>,
        "'David S. Miller'" <davem@...emloft.net>,
        'Rob Herring' <robh@...nel.org>,
        'Anton Blanchard' <anton@...abs.org>,
        'Krzysztof Kozlowski' <krzk@...nel.org>,
        'Mahesh Salgaonkar' <mahesh@...ux.vnet.ibm.com>,
        'Madhavan Srinivasan' <maddy@...ux.vnet.ibm.com>,
        'Cédric Le Goater' <clg@...d.org>,
        'Anju T Sudhakar' <anju@...ux.vnet.ibm.com>,
        'Hari Bathini' <hbathini@...ux.ibm.com>,
        'Thomas Gleixner' <tglx@...utronix.de>,
        'Nicholas Piggin' <npiggin@...il.com>,
        'Masahiro Yamada' <yamada.masahiro@...ionext.com>,
        'Alexey Kardashevskiy' <aik@...abs.ru>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 04/27] ocxl: Remove unnecessary externs

On 02/26/20 at 03:20pm, Greg Kurz wrote:
> On Wed, 26 Feb 2020 22:15:23 +0800
> 'Baoquan He' <bhe@...hat.com> wrote:
> 
> > On 02/26/20 at 10:01am, Greg Kurz wrote:
> > > On Wed, 26 Feb 2020 19:26:34 +1100
> > > "Alastair D'Silva" <alastair@...ilva.org> wrote:
> > > 
> > > > > -----Original Message-----
> > > > > From: Baoquan He <bhe@...hat.com>
> > > > > Sent: Wednesday, 26 February 2020 7:15 PM
> > > > > To: Alastair D'Silva <alastair@....ibm.com>
> > > > > Cc: alastair@...ilva.org; Aneesh Kumar K . V
> > > > > <aneesh.kumar@...ux.ibm.com>; Oliver O'Halloran <oohall@...il.com>;
> > > > > Benjamin Herrenschmidt <benh@...nel.crashing.org>; Paul Mackerras
> > > > > <paulus@...ba.org>; Michael Ellerman <mpe@...erman.id.au>; Frederic
> > > > > Barrat <fbarrat@...ux.ibm.com>; Andrew Donnellan <ajd@...ux.ibm.com>;
> > > > > Arnd Bergmann <arnd@...db.de>; Greg Kroah-Hartman
> > > > > <gregkh@...uxfoundation.org>; Dan Williams <dan.j.williams@...el.com>;
> > > > > Vishal Verma <vishal.l.verma@...el.com>; Dave Jiang
> > > > > <dave.jiang@...el.com>; Ira Weiny <ira.weiny@...el.com>; Andrew Morton
> > > > > <akpm@...ux-foundation.org>; Mauro Carvalho Chehab
> > > > > <mchehab+samsung@...nel.org>; David S. Miller <davem@...emloft.net>;
> > > > > Rob Herring <robh@...nel.org>; Anton Blanchard <anton@...abs.org>;
> > > > > Krzysztof Kozlowski <krzk@...nel.org>; Mahesh Salgaonkar
> > > > > <mahesh@...ux.vnet.ibm.com>; Madhavan Srinivasan
> > > > > <maddy@...ux.vnet.ibm.com>; Cédric Le Goater <clg@...d.org>; Anju T
> > > > > Sudhakar <anju@...ux.vnet.ibm.com>; Hari Bathini
> > > > > <hbathini@...ux.ibm.com>; Thomas Gleixner <tglx@...utronix.de>; Greg
> > > > > Kurz <groug@...d.org>; Nicholas Piggin <npiggin@...il.com>; Masahiro
> > > > > Yamada <yamada.masahiro@...ionext.com>; Alexey Kardashevskiy
> > > > > <aik@...abs.ru>; linux-kernel@...r.kernel.org; linuxppc-
> > > > > dev@...ts.ozlabs.org; linux-nvdimm@...ts.01.org; linux-mm@...ck.org
> > > > > Subject: Re: [PATCH v3 04/27] ocxl: Remove unnecessary externs
> > > > > 
> > > > > On 02/21/20 at 02:26pm, Alastair D'Silva wrote:
> > > > > > From: Alastair D'Silva <alastair@...ilva.org>
> > > > > >
> > > > > > Function declarations don't need externs, remove the existing ones so
> > > > > > they are consistent with newer code
> > > > > >
> > > > > > Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
> > > > > > ---
> > > > > >  arch/powerpc/include/asm/pnv-ocxl.h | 32 ++++++++++++++---------------
> > > > > >  include/misc/ocxl.h                 |  6 +++---
> > > > > >  2 files changed, 18 insertions(+), 20 deletions(-)
> > > > > >
> > > > > > diff --git a/arch/powerpc/include/asm/pnv-ocxl.h
> > > > > > b/arch/powerpc/include/asm/pnv-ocxl.h
> > > > > > index 0b2a6707e555..b23c99bc0c84 100644
> > > > > > --- a/arch/powerpc/include/asm/pnv-ocxl.h
> > > > > > +++ b/arch/powerpc/include/asm/pnv-ocxl.h
> > > > > > @@ -9,29 +9,27 @@
> > > > > >  #define PNV_OCXL_TL_BITS_PER_RATE       4
> > > > > >  #define PNV_OCXL_TL_RATE_BUF_SIZE
> > > > > ((PNV_OCXL_TL_MAX_TEMPLATE+1) * PNV_OCXL_TL_BITS_PER_RATE / 8)
> > > > > >
> > > > > > -extern int pnv_ocxl_get_actag(struct pci_dev *dev, u16 *base, u16
> > > > > *enabled,
> > > > > > -			u16 *supported);
> > > > > 
> > > > > It works w or w/o extern when declare functions. Searching 'extern'
> > > > > under include can find so many functions with 'extern' adding. Do we have
> > > > a
> > > > > explicit standard if we should add or remove 'exter' in function
> > > > declaration?
> > > > > 
> > > > > I have no objection to this patch, just want to make clear so that I can
> > > > handle
> > > > > it w/o confusion.
> > > > > 
> > > > > Thanks
> > > > > Baoquan
> > > > > 
> > > > 
> > > > For the OpenCAPI driver, we have settled on not having 'extern' on
> > > > functions.
> > > > 
> > > > I don't think I've seen a standard that supports or refutes this, but it
> > > > does not value add.
> > > > 
> > > 
> > > FWIW this is a warning condition for checkpatch:
> > > 
> > > $ ./scripts/checkpatch.pl --strict -f include/misc/ocxl.h
> > 
> > Good to know, thanks.
> > 
> > I didn't know checkpatch.pl can run on header file directly. Tried to
> > check patch with '--strict -f', the below info doesn't appear. But it
> 
> Hmm... -f is to check a source file, not a patch... What did you try
> exactly ?

OK, that's it. I can see the 'CHECK' line when run checkpatch.pl on
patch with '--strict' only. I think this can be a good reason that we
should not add extern when add function declaration into header file.
Thanks.

> 
> > does give out below information when run on header file.
> > 
> > > 
> > > [...]
> > > 
> > > CHECK: extern prototypes should be avoided in .h files
> > > #176: FILE: include/misc/ocxl.h:176:
> > > +extern int ocxl_afu_irq_alloc(struct ocxl_context *ctx, int *irq_id);
> > > 
> > > [...]
> > > 
> > 
> 
>