linux-kernel - Re: [PATCH] drm/bridge: anx7625: check the return on anx7625_aux

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Message-ID: <CAG3jFyuBuJmr=NJROWHyEQqW9qng6KtwhJ1a9ACUEGfZ7g-Mxg@mail.gmail.com>
Date:   Wed, 9 Mar 2022 14:48:18 +0100
From:   Robert Foss <robert.foss@...aro.org>
To:     Tom Rix <trix@...hat.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        andrzej.hajda@...el.com, narmstrong@...libre.com,
        laurent.pinchart@...asonboard.com, jonas@...boo.se,
        jernej.skrabec@...il.com, airlied@...ux.ie, daniel@...ll.ch,
        nathan@...nel.org, xji@...logixsemi.com, sam@...nborg.org,
        tzungbi@...gle.com, pihsun@...omium.org, maxime@...no.tech,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, hsinyi@...omium.org
Subject: Re: [PATCH] drm/bridge: anx7625: check the return on anx7625_aux_trans

On Wed, 9 Mar 2022 at 02:45, Tom Rix <trix@...hat.com> wrote:
>
>
> On 3/8/22 2:57 PM, Nick Desaulniers wrote:
> > On Thu, Mar 3, 2022 at 12:19 PM <trix@...hat.com> wrote:
> >> From: Tom Rix <trix@...hat.com>
> >>
> >> Clang static analysis reports this issue
> >> anx7625.c:876:13: warning: The left operand of '&' is
> >>    a garbage value
> >>    if (!(bcap & 0xOA01)) {
> >>          ~~~~ ^
> >>
> >> bcap is only set by a successful call to
> >> anx7625_aux_trans().  So check.
> >>
> >> Fixes: cd1637c7e480 ("drm/bridge: anx7625: add HDCP support")
> > Is this the correct Fixes tag?
> yes
> > I think it should be
> >
> > Fixes: adca62ec370c ("drm/bridge: anx7625: Support reading edid
> > through aux channel")
>
> This one changes the name of the function
>
> -       anx7625_aux_dpcd_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
> +       anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
>
> A return check from the earlier commit, when this block of code came
> into existence, is when it was first needed.
>
> Tom
>
> >
> > instead.
> >
> >> Signed-off-by: Tom Rix <trix@...hat.com>
> >> ---
> >>   drivers/gpu/drm/bridge/analogix/anx7625.c | 5 ++++-
> >>   1 file changed, 4 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> >> index 633618bafd75d..f02ac079ed2ec 100644
> >> --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> >> +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> >> @@ -872,7 +872,10 @@ static int anx7625_hdcp_enable(struct anx7625_data *ctx)
> >>          }
> >>
> >>          /* Read downstream capability */
> >> -       anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
> >> +       ret = anx7625_aux_trans(ctx, DP_AUX_NATIVE_READ, 0x68028, 1, &bcap);
> >> +       if (ret < 0)
> >> +               return ret;
> >> +
> >>          if (!(bcap & 0x01)) {
> >>                  pr_warn("downstream not support HDCP 1.4, cap(%x).\n", bcap);
> >>                  return 0;
> >> --
> >> 2.26.3
> >>
> >
>

Reviewed-by: Robert Foss <robert.foss@...aro.org>

Applied to drm-misc-next.