* drm_dp_mst_topology.c and old compilers
@ 2020-02-20 0:42 Paul E. McKenney
2020-02-20 2:52 ` Alex Deucher
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Paul E. McKenney @ 2020-02-20 0:42 UTC (permalink / raw)
To: maarten.lankhorst, mripard, airlied, daniel; +Cc: dri-devel, linux-kernel
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?
Thanx, Paul
-----------------------------------------------------------------------
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 20cdaf3..232408a 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 = {{{ 0 }}};
u8 endpoint_fec;
u8 endpoint_dsc;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: drm_dp_mst_topology.c and old compilers
2020-02-20 0:42 drm_dp_mst_topology.c and old compilers Paul E. McKenney
@ 2020-02-20 2:52 ` Alex Deucher
2020-02-20 7:58 ` Chris Wilson
2020-02-20 11:59 ` Joe Perches
2020-02-20 15:07 ` Christoph Hellwig
2 siblings, 1 reply; 6+ messages in thread
From: Alex Deucher @ 2020-02-20 2:52 UTC (permalink / raw)
To: paulmck
Cc: Maarten Lankhorst, Maxime Ripard, Dave Airlie, Daniel Vetter,
LKML, Maling list - DRI developers
On Wed, Feb 19, 2020 at 7:42 PM Paul E. McKenney <paulmck@kernel.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.
Alex
>
> Thanx, Paul
>
> -----------------------------------------------------------------------
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 20cdaf3..232408a 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 = {{{ 0 }}};
> u8 endpoint_fec;
> u8 endpoint_dsc;
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: drm_dp_mst_topology.c and old compilers
2020-02-20 2:52 ` Alex Deucher
@ 2020-02-20 7:58 ` Chris Wilson
2020-02-20 18:36 ` Paul E. McKenney
0 siblings, 1 reply; 6+ messages in thread
From: Chris Wilson @ 2020-02-20 7:58 UTC (permalink / raw)
To: Alex Deucher, paulmck; +Cc: Dave Airlie, LKML, Maling list - DRI developers
Quoting Alex Deucher (2020-02-20 02:52:32)
> On Wed, Feb 19, 2020 at 7:42 PM Paul E. McKenney <paulmck@kernel.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
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: drm_dp_mst_topology.c and old compilers
2020-02-20 0:42 drm_dp_mst_topology.c and old compilers Paul E. McKenney
2020-02-20 2:52 ` Alex Deucher
@ 2020-02-20 11:59 ` Joe Perches
2020-02-20 15:07 ` Christoph Hellwig
2 siblings, 0 replies; 6+ messages in thread
From: Joe Perches @ 2020-02-20 11:59 UTC (permalink / raw)
To: paulmck, maarten.lankhorst, mripard, airlied, daniel
Cc: dri-devel, linux-kernel
On Wed, 2020-02-19 at 16:42 -0800, Paul E. McKenney 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?
[]
> diff --git 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 = {{{ 0 }}};
Perhaps this is simpler as:
struct drm_dp_desc desc = {};
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: drm_dp_mst_topology.c and old compilers
2020-02-20 0:42 drm_dp_mst_topology.c and old compilers Paul E. McKenney
2020-02-20 2:52 ` Alex Deucher
2020-02-20 11:59 ` Joe Perches
@ 2020-02-20 15:07 ` Christoph Hellwig
2 siblings, 0 replies; 6+ messages in thread
From: Christoph Hellwig @ 2020-02-20 15:07 UTC (permalink / raw)
To: Paul E. McKenney
Cc: maarten.lankhorst, mripard, airlied, daniel, dri-devel, linux-kernel
On Wed, Feb 19, 2020 at 04:42:33PM -0800, Paul E. McKenney wrote:
> - struct drm_dp_desc desc = { 0 };
> + struct drm_dp_desc desc = {{{ 0 }}};
Does:
struct drm_dp_desc desc = { };
work for your geriatric compiler?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: drm_dp_mst_topology.c and old compilers
2020-02-20 7:58 ` Chris Wilson
@ 2020-02-20 18:36 ` Paul E. McKenney
0 siblings, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2020-02-20 18:36 UTC (permalink / raw)
To: Chris Wilson
Cc: Alex Deucher, Dave Airlie, LKML, Maling list - DRI developers
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@kernel.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@kernel.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@chris-wilson.co.uk>
Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.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;
^ permalink raw reply related [flat|nested] 6+ messages in thread
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2020-02-20 0:42 drm_dp_mst_topology.c and old compilers Paul E. McKenney
2020-02-20 2:52 ` Alex Deucher
2020-02-20 7:58 ` Chris Wilson
2020-02-20 18:36 ` Paul E. McKenney
2020-02-20 11:59 ` Joe Perches
2020-02-20 15:07 ` Christoph Hellwig
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