linux-kernel - Re: drm_dp_mst_topology.c and old compilers

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Message-ID: <20200220183621.GW2935@paulmck-ThinkPad-P72>
Date:   Thu, 20 Feb 2020 10:36:21 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Alex Deucher <alexdeucher@...il.com>,
        Dave Airlie <airlied@...ux.ie>,
        LKML <linux-kernel@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>
Subject: Re: drm_dp_mst_topology.c and old compilers

On Thu, Feb 20, 2020 at 07:58:58AM +0000, Chris Wilson wrote:
> Quoting Alex Deucher (2020-02-20 02:52:32)
> > On Wed, Feb 19, 2020 at 7:42 PM Paul E. McKenney <paulmck@...nel.org> wrote:
> > >
> > > Hello!
> > >
> > > A box with GCC 4.8.3 compiler didn't like drm_dp_mst_topology.c.  The
> > > following (lightly tested) patch makes it happy and seems OK for newer
> > > compilers as well.
> > >
> > > Is this of interest?
> > 
> > How about a memset instead?  That should be consistent across compilers.
> 
> The kernel has adopted the gccism: struct drm_dp_desc desc = {};
> git grep '= {}' | wc -l: 2046
> git grep '= { }' | wc -l: 694
> -Chris

And this works well, a big "thank you!" to all three of you!

Please see below for the updated patch.

							Thanx, Paul

------------------------------------------------------------------------

commit 78c0e53a98a9772a99e46806f8fcbe1140d667a4
Author: Paul E. McKenney <paulmck@...nel.org>
Date:   Wed Feb 19 16:42:47 2020 -0800

    EXP drm: Make drm_dp_mst_dsc_aux_for_port() safe for old compilers
    
    Older compilers either want two extra pairs of curly braces around the
    initializer for local variable desc, or they want a single pair of curly
    braces with nothing inside.  Current Linux-kernel practice favors the
    latter, so this commit makes it so.
    
    Suggested-by: Chris Wilson <chris@...is-wilson.co.uk>
    Suggested-by: Joe Perches <joe@...ches.com>
    Suggested-by: Christoph Hellwig <hch@...radead.org>
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 20cdaf3..b123f60 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -5396,7 +5396,7 @@ struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
 {
 	struct drm_dp_mst_port *immediate_upstream_port;
 	struct drm_dp_mst_port *fec_port;
-	struct drm_dp_desc desc = { 0 };
+	struct drm_dp_desc desc = { };
 	u8 endpoint_fec;
 	u8 endpoint_dsc;