linux-kernel - Re: [PATCH v2 9/9] drm/bridge: ti-sn65dsi86: Avoid invalid rates

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Message-ID: <CAD=FV=Ui=ZbzdyV6SjLvrL-zj6e+upog_wZMG4seOsdgZpF6tg@mail.gmail.com>
Date:   Mon, 6 Jan 2020 14:43:28 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     kbuild test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Rob Clark <robdclark@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Jonas Karlman <jonas@...boo.se>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sean Paul <seanpaul@...omium.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 9/9] drm/bridge: ti-sn65dsi86: Avoid invalid rates

Dear Robot,

On Sat, Dec 21, 2019 at 5:57 AM kbuild test robot <lkp@...el.com> wrote:
>
> Hi Douglas,
>
> I love your patch! Perhaps something to improve:
>
> [auto build test WARNING on linus/master]
> [also build test WARNING on v5.5-rc2 next-20191220]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
>
> url:    https://github.com/0day-ci/linux/commits/Douglas-Anderson/drm-bridge-ti-sn65dsi86-Improve-support-for-AUO-B116XAK01-other-DP/20191221-083448
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 7e0165b2f1a912a06e381e91f0f4e495f4ac3736
> config: sh-allmodconfig (attached as .config)
> compiler: sh4-linux-gcc (GCC) 7.5.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.5.0 make.cross ARCH=sh
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@...el.com>
>
> Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
> http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings
>
> All warnings (new ones prefixed by >>):
>
>    drivers/gpu/drm/bridge/ti-sn65dsi86.c: In function 'ti_sn_bridge_enable':
> >> drivers/gpu/drm/bridge/ti-sn65dsi86.c:543:18: warning: 'rate_valid' may be used uninitialized in this function [-Wmaybe-uninitialized]
>        if (rate_valid[i])
>            ~~~~~~~~~~^~~

I love your report!  Interestingly I had already noticed this problem
myself and v3 of the patch fixes the issue.  See:

https://lore.kernel.org/r/20191218143416.v3.9.Ib59207b66db377380d13748752d6fce5596462c5@changeid


If the maintainer of the robot is reading this, something to improve
about your robot is that it could have noticed v3 of the patch (which
was posted several days before your report) and skipped analyzing v2
of the patch.  I'm currently using Change-Ids embedded in my
Message-Id to help automation relate one version of my patches to the
next.  Specifically you compare the Message-Id of v2 and v3 of this
patch:

20191217164702.v2.9.Ib59207b66db377380d13748752d6fce5596462c5@...ngeid
20191218143416.v3.9.Ib59207b66db377380d13748752d6fce5596462c5@...ngeid

Since the last section before the "@changeid" remained constant it
could be assumed that this patch replaced the v2.  I know there's not
too much usage of this technique yet, but if only more tools supported
it then maybe more people would use it.


-Doug