linux-kernel - Re: [PATCH] drm/gma500/oaktrail_lvds: replace continue with break

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Message-ID: <CAMeQTsaN-GYzix6X18bWxKY1L13bTrUUYDmp6tFdvaERZEj=3g@mail.gmail.com>
Date:   Sat, 19 Jun 2021 22:43:47 +0200
From:   Patrik Jakobsson <patrik.r.jakobsson@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Colin King <colin.king@...onical.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        kernel-janitors@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/gma500/oaktrail_lvds: replace continue with break

On Sat, Jun 19, 2021 at 3:40 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> On Fri, Jun 18, 2021 at 07:35:24PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> >
> > Currently a loop scans through the connector list checking
> > for connectors that do not match a specific criteria. The
> > use of the continue statement is a little unintuitive and
> > can confuse static analysis checking.  Invert the criteria
> > matching logic and use a break to terminate the loop once
> > the first suitable connector has been found.
> >
> > Thanks to Patrik Jakobsson for explaining the original
> > intent of the code and suggesting this change.
> >
> > Addresses-Coverity: ("Continue has no effect")
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  drivers/gpu/drm/gma500/oaktrail_lvds.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/gma500/oaktrail_lvds.c b/drivers/gpu/drm/gma500/oaktrail_lvds.c
> > index 432bdcc57ac9..8541dcf237eb 100644
> > --- a/drivers/gpu/drm/gma500/oaktrail_lvds.c
> > +++ b/drivers/gpu/drm/gma500/oaktrail_lvds.c
> > @@ -113,8 +113,8 @@ static void oaktrail_lvds_mode_set(struct drm_encoder *encoder,
> >
> >       /* Find the connector we're trying to set up */
> >       list_for_each_entry(connector, &mode_config->connector_list, head) {
> > -             if (!connector->encoder || connector->encoder->crtc != crtc)
> > -                     continue;
> > +             if (connector->encoder && connector->encoder->crtc == crtc)
> > +                     break;
> >       }
> >
> >       if (!connector) {
>
> This test is wrong/impossible.  It should be:
>
>         if (list_entry_is_head(connector, &mode_config->connector_list,
>                                head)) {

Right, we should be back at the head if no match was found. Actually,
when looking closer, we should use drm_for_each_connector_iter() when
walking the connector list together with proper locking.

-Patrik

>
> regards,
> dan carpenter
>
>