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Subject: Re: [PATCH] drm/bridge: anx7625: check the return on
 anx7625_aux_trans
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     andrzej.hajda@intel.com, narmstrong@baylibre.com,
        robert.foss@linaro.org, laurent.pinchart@ideasonboard.com,
        jonas@kwiboo.se, jernej.skrabec@gmail.com, airlied@linux.ie,
        daniel@ffwll.ch, nathan@kernel.org, xji@analogixsemi.com,
        sam@ravnborg.org, tzungbi@google.com, pihsun@chromium.org,
        maxime@cerno.tech, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        hsinyi@chromium.org
References: <20220303201943.501746-1-trix@redhat.com>
 <CAKwvOdnoV_SsFuWWJd4nOOd1vGG6_-gg-KvdOg4_NHuRp7_WfA@mail.gmail.com>
From:   Tom Rix <trix@redhat.com>
Message-ID: <5b6a10bd-5650-2924-d1cc-e4664a0e7255@redhat.com>
Date:   Tue, 8 Mar 2022 17:45:41 -0800
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On 3/8/22 2:57 PM, Nick Desaulniers wrote:
> On Thu, Mar 3, 2022 at 12:19 PM <trix@redhat.com> wrote:
>> From: Tom Rix <trix@redhat.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@redhat.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
>>
>