linux-kernel - RE: [PATCH] drm/amdgpu: do not initialise global variables to 0 or NULL

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Date:   Mon, 2 Nov 2020 22:30:45 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Greg KH' <gregkh@...uxfoundation.org>,
        Alex Deucher <alexdeucher@...il.com>
CC:     Deepak R Varma <mh12gx2825@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        "Maling list - DRI developers" <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Melissa Wen <melissa.srw@...il.com>,
        "Daniel Vetter" <daniel.vetter@...ll.ch>
Subject: RE: [PATCH] drm/amdgpu: do not initialise global variables to 0 or
 NULL

From: Greg KH
> Sent: 02 November 2020 20:11
> 
> On Mon, Nov 02, 2020 at 02:43:45PM -0500, Alex Deucher wrote:
> > On Mon, Nov 2, 2020 at 1:42 PM Deepak R Varma <mh12gx2825@...il.com> wrote:
> > >
> > > Initializing global variable to 0 or NULL is not necessary and should
> > > be avoided. Issue reported by checkpatch script as:
> > > ERROR: do not initialise globals to 0 (or NULL).
> >
> > I agree that this is technically correct, but a lot of people don't
> > seem to know that so we get a lot of comments about this code for the
> > variables that are not explicitly set.  Seems less confusing to
> > initialize them even if it not necessary.  I don't have a particularly
> > strong opinion on it however.
> 
> The kernel coding style is to do it this way.  You even save space and
> time by doing it as well :)

Uninitialised globals end up as 'named common' (variables that are
their own code section - from FORTRAN) until the final link puts
them into the .bss.
Globals initialised to 0 go into the .bss of the object file
being created.

So both end up in the final .bss.

If the code goes into a module you aren't allowed 'common' data
in a module to every global must be initialised.

I'm surprised checkpatch complains.

	David

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