linux-kernel - RE: [PATCH] drm/amd/display: Don't take the address of skip_scdc_overwrite in dc_link_detect

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Date:   Fri, 14 Feb 2020 16:01:01 +0000
From:   "Liu, Zhan" <Zhan.Liu@....com>
To:     Nathan Chancellor <natechancellor@...il.com>,
        "Wentland, Harry" <Harry.Wentland@....com>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>
CC:     "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] drm/amd/display: Don't take the address of
 skip_scdc_overwrite in dc_link_detect_helper



> -----Original Message-----
> From: dri-devel <dri-devel-bounces@...ts.freedesktop.org> On Behalf Of
> Nathan Chancellor
> Sent: 2020/February/14, Friday 1:30 AM
> To: Wentland, Harry <Harry.Wentland@....com>; Li, Sun peng (Leo)
> <Sunpeng.Li@....com>; Deucher, Alexander
> <Alexander.Deucher@....com>; Koenig, Christian
> <Christian.Koenig@....com>; Zhou, David(ChunMing)
> <David1.Zhou@....com>
> Cc: clang-built-linux@...glegroups.com; Nathan Chancellor
> <natechancellor@...il.com>; dri-devel@...ts.freedesktop.org; amd-
> gfx@...ts.freedesktop.org; linux-kernel@...r.kernel.org
> Subject: [PATCH] drm/amd/display: Don't take the address of
> skip_scdc_overwrite in dc_link_detect_helper
> 
> Clang warns:
> 
> ../drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c:980:36:
> warning: address of 'sink->edid_caps.panel_patch.skip_scdc_overwrite'
> will always evaluate to 'true' [-Wpointer-bool-conversion]
>                 if (&sink->edid_caps.panel_patch.skip_scdc_overwrite)
>                 ~~   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
> 1 warning generated.
> 
> This is probably not what was intended so remove the address of operator,
> which matches how skip_scdc_overwrite is handled in the rest of the driver.
> 
> While we're here, drop an extra newline after this if block.
> 
> Fixes: a760fc1bff03 ("drm/amd/display: add monitor patch to disable SCDC
> read/write")
> Link:
> https://github.com/ClangBuiltLinux/linux/issues/879
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>

Thank you!
Reviewed-by: Zhan Liu <zhan.liu@....com>

> ---
> 
> As an aside, I don't see skip_scdc_overwrite assigned a value anywhere, is
> this working as intended?
> 
>  drivers/gpu/drm/amd/display/dc/core/dc_link.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> index 24d99849be5e..a3bfa05c545e 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> @@ -977,10 +977,9 @@ static bool dc_link_detect_helper(struct dc_link
> *link,
>  		if ((prev_sink != NULL) && ((edid_status == EDID_THE_SAME)
> || (edid_status == EDID_OK)))
>  			same_edid = is_same_edid(&prev_sink->dc_edid,
> &sink->dc_edid);
> 
> -		if (&sink->edid_caps.panel_patch.skip_scdc_overwrite)
> +		if (sink->edid_caps.panel_patch.skip_scdc_overwrite)
>  			link->ctx->dc->debug.hdmi20_disable = true;
> 
> -
>  		if (link->connector_signal == SIGNAL_TYPE_DISPLAY_PORT
> &&
>  			sink_caps.transaction_type ==
> DDC_TRANSACTION_TYPE_I2C_OVER_AUX) {
>  			/*
> --
> 2.25.0
> 
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