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From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Thu, 7 May 2020 15:41:31 -0400
Message-ID: <CADnq5_MDPZbDrrgCCdWVfSX47it0=JvTj3k_W8woK6=O=qzCnQ@mail.gmail.com>
Subject: Re: [PATCH -next] drm/amd/dc: Remove a useless comparison
To:     ChenTao <chentao107@huawei.com>
Cc:     Dave Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        "Cyr, Aric" <Aric.Cyr@amd.com>,
        "Leo (Sunpeng) Li" <sunpeng.li@amd.com>,
        Anthony Koo <Anthony.Koo@amd.com>,
        "Siqueira, Rodrigo" <Rodrigo.Siqueira@amd.com>, murton.liu@amd.com,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@lists.freedesktop.org>,
        "Wentland, Harry" <harry.wentland@amd.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Christian Koenig <christian.koenig@amd.com>,
        Su Sung Chung <Su.Chung@amd.com>
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On Thu, May 7, 2020 at 9:35 AM ChenTao <chentao107@huawei.com> wrote:
>
> Fix the following warning:
>
> 'en' is uint32_t and can never be negative.
>
> drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/hw_hpd.c:132:10: warning:
> comparison of unsigned expression < 0 is always false [-Wtype-limits]
>   if ((en < GPIO_DDC_LINE_MIN) || (en > GPIO_DDC_LINE_MAX)) {
> drivers/gpu/drm/amd/amdgpu/../display/dc/gpio/hw_generic.c:109:10: warning:
> comparison of unsigned expression < 0 is always false [-Wtype-limits]
>   if ((en < GPIO_DDC_LINE_MIN) || (en > GPIO_DDC_LINE_MAX)) {
>

While it's not required, I think it improves readability and protects
if the enum has negative values.  I think it would be better to change
the en var to signed.

Alex

> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: ChenTao <chentao107@huawei.com>
> ---
>  drivers/gpu/drm/amd/display/dc/gpio/hw_generic.c | 2 +-
>  drivers/gpu/drm/amd/display/dc/gpio/hw_hpd.c     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/gpio/hw_generic.c b/drivers/gpu/drm/amd/display/dc/gpio/hw_generic.c
> index f9e847e6555d..6cd50232c432 100644
> --- a/drivers/gpu/drm/amd/display/dc/gpio/hw_generic.c
> +++ b/drivers/gpu/drm/amd/display/dc/gpio/hw_generic.c
> @@ -106,7 +106,7 @@ void dal_hw_generic_init(
>         enum gpio_id id,
>         uint32_t en)
>  {
> -       if ((en < GPIO_DDC_LINE_MIN) || (en > GPIO_DDC_LINE_MAX)) {
> +       if (en > GPIO_DDC_LINE_MAX) {
>                 ASSERT_CRITICAL(false);
>                 *hw_generic = NULL;
>         }
> diff --git a/drivers/gpu/drm/amd/display/dc/gpio/hw_hpd.c b/drivers/gpu/drm/amd/display/dc/gpio/hw_hpd.c
> index 692f29de7797..f91f426699c0 100644
> --- a/drivers/gpu/drm/amd/display/dc/gpio/hw_hpd.c
> +++ b/drivers/gpu/drm/amd/display/dc/gpio/hw_hpd.c
> @@ -129,7 +129,7 @@ void dal_hw_hpd_init(
>         enum gpio_id id,
>         uint32_t en)
>  {
> -       if ((en < GPIO_DDC_LINE_MIN) || (en > GPIO_DDC_LINE_MAX)) {
> +       if (en > GPIO_DDC_LINE_MAX) {
>                 ASSERT_CRITICAL(false);
>                 *hw_hpd = NULL;
>         }
> --
> 2.22.0
>
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