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

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Date:   Wed, 17 Jan 2018 09:23:52 +0100
From:   Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH] [RESEND] drm/gma500: initialize gma_clock_t structures

On Tue, Jan 16, 2018 at 3:57 PM, Arnd Bergmann <arnd@...db.de> wrote:
> 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>

Dave or Daniel, I'm on sick leave and will be for some time to come.
Can one of you pick up this patch? Thanks.

Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@...il.com>

> ---
> 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
>