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

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Date:   Tue, 3 Nov 2020 08:53:55 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christian König <christian.koenig@....com>
Cc:     Alex Deucher <alexdeucher@...il.com>,
        Deepak R Varma <mh12gx2825@...il.com>,
        David Airlie <airlied@...ux.ie>,
        LKML <linux-kernel@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Melissa Wen <melissa.srw@...il.com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH] drm/amdgpu: do not initialise global variables to 0 or
 NULL

On Mon, Nov 02, 2020 at 09:48:25PM +0100, Christian König wrote:
> Am 03.11.20 um 07:53 schrieb Greg KH:
> > On Mon, Nov 02, 2020 at 09:06:21PM +0100, Christian König wrote:
> > > Am 02.11.20 um 20:43 schrieb Alex Deucher:
> > > > 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.
> > > Agree with Alex.
> > > 
> > > Especially for the module parameters we should have a explicit init value
> > > for documentation purposes, even when it is 0.
> > Why is this one tiny driver somehow special compared to the entire rest
> > of the kernel?  (hint, it isn't...)
> 
> And it certainly shouldn't :)
> 
> > Please follow the normal coding style rules, there's no reason to ignore
> > them unless you like to constantly reject patches like this that get
> > sent to you.
> 
> Yeah, that's a rather good point.
> 
> Not a particular strong opinion on this either, but when something global is
> set to 0 people usually do this to emphases that it is important that it is
> zero.

Again, no, that's not what we have been doing in the kernel for the past
20+ years.  If you do not set it to anything, we all know it is
important for it to be set to 0.  Otherwise we would explicitly set it
to something else.  And if we don't care, then that too doesn't matter
so we let it be 0 by not initializing it, it doesn't matter.

I think this very change is what started the whole "kernel janitor"
movement all those years ago, because it was easily proven that this
simple change saved both time and memory.

This shouldn't even be an argument we are having anymore...

thanks,

greg k-h