linux-kernel - [PATCH] [RESEND] drm/gma500: initialize gma_clock

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Message-Id: <20180116145720.2348043-1-arnd@arndb.de>
Date:   Tue, 16 Jan 2018 15:57:10 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        David Airlie <airlied@...ux.ie>
Cc:     Arnd Bergmann <arnd@...db.de>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] [RESEND] drm/gma500: initialize gma_clock_t structures

The two functions pass a partially initialized structure back to the
caller after a memset() on the destination.

This is not entirely well-defined, most compilers are sensible enough
to either keep the zero-initialization for the uninitialized members,
but gcc-4.4 does not, and it warns about this:

drivers/gpu/drm/gma500/oaktrail_crtc.c: In function 'mrst_sdvo_find_best_pll':
drivers/gpu/drm/gma500/oaktrail_crtc.c:175: warning: 'clock.vco' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:175: warning: 'clock.dot' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:175: warning: 'clock.p2' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:175: warning: 'clock.m2' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:175: warning: 'clock.m1' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c: In function 'mrst_lvds_find_best_pll':
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.p' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.vco' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.p2' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.m2' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.m1' may be used uninitialized in this function
drivers/gpu/drm/gma500/oaktrail_crtc.c:208: warning: 'clock.n' may be used uninitialized in this function

This adds an initialization at declaration time to avoid the warning
and make it well-defined on all compiler versions.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Originally submitted on Sep 15, 2017, but got no reply. Resending unchanged.
---
 drivers/gpu/drm/gma500/oaktrail_crtc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/gma500/oaktrail_crtc.c b/drivers/gpu/drm/gma500/oaktrail_crtc.c
index 0fff269d3fe6..b49fe79c3f44 100644
--- a/drivers/gpu/drm/gma500/oaktrail_crtc.c
+++ b/drivers/gpu/drm/gma500/oaktrail_crtc.c
@@ -134,7 +134,7 @@ static bool mrst_sdvo_find_best_pll(const struct gma_limit_t *limit,
 				    struct drm_crtc *crtc, int target,
 				    int refclk, struct gma_clock_t *best_clock)
 {
-	struct gma_clock_t clock;
+	struct gma_clock_t clock = {};
 	u32 target_vco, actual_freq;
 	s32 freq_error, min_error = 100000;
 
@@ -191,7 +191,7 @@ static bool mrst_lvds_find_best_pll(const struct gma_limit_t *limit,
 				    struct drm_crtc *crtc, int target,
 				    int refclk, struct gma_clock_t *best_clock)
 {
-	struct gma_clock_t clock;
+	struct gma_clock_t clock = {};
 	int err = target;
 
 	memset(best_clock, 0, sizeof(*best_clock));
-- 
2.9.0