linux-kernel - Re: [PATCH] drm/msm: Fix return type of mdp4_lvds_connector_mode

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Date:   Mon, 31 Oct 2022 17:26:52 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nathan Huckleberry <nhuck@...gle.com>
CC:     Dan Carpenter <error27@...il.com>, <llvm@...ts.linux.dev>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm: Fix return type of
 mdp4_lvds_connector_mode_valid



On 10/31/2022 5:24 PM, Dmitry Baryshkov wrote:
> On 01/11/2022 01:10, Nathan Chancellor wrote:
>> On Tue, Sep 13, 2022 at 01:55:48PM -0700, Nathan Huckleberry wrote:
>>> The mode_valid field in drm_connector_helper_funcs is expected to be of
>>> type:
>>> enum drm_mode_status (* mode_valid) (struct drm_connector *connector,
>>>                                       struct drm_display_mode *mode);
>>>
>>> The mismatched return type breaks forward edge kCFI since the underlying
>>> function definition does not match the function hook definition.
>>>
>>> The return type of mdp4_lvds_connector_mode_valid should be changed from
>>> int to enum drm_mode_status.
>>>
>>> Reported-by: Dan Carpenter <error27@...il.com>
>>> Link: https://github.com/ClangBuiltLinux/linux/issues/1703
>>> Cc: llvm@...ts.linux.dev
>>> Signed-off-by: Nathan Huckleberry <nhuck@...gle.com>
>>> ---
>>>   drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c | 5 +++--
>>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c 
>>> b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
>>> index 7288041dd86a..7444b75c4215 100644
>>> --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
>>> +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
>>> @@ -56,8 +56,9 @@ static int mdp4_lvds_connector_get_modes(struct 
>>> drm_connector *connector)
>>>       return ret;
>>>   }
>>> -static int mdp4_lvds_connector_mode_valid(struct drm_connector 
>>> *connector,
>>> -                 struct drm_display_mode *mode)
>>> +static enum drm_mode_status
>>> +mdp4_lvds_connector_mode_valid(struct drm_connector *connector,
>>> +                   struct drm_display_mode *mode)
>>>   {
>>>       struct mdp4_lvds_connector *mdp4_lvds_connector =
>>>               to_mdp4_lvds_connector(connector);
>>> -- 
>>> 2.37.2.789.g6183377224-goog
>>>
>>>
>>
>> Did this patch get lost somewhere? I do not see it picked up. It is
>> needed to avoid a new WIP warning from clang for catching these CFI
>> failures:
>>
>> drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c:89:16: error: 
>> incompatible function pointer types initializing 'enum drm_mode_status 
>> (*)(struct drm_connector *, struct drm_display_mode *)' with an 
>> expression of type 'int (struct drm_connector *, struct 
>> drm_display_mode *)' 
>> [-Werror,-Wincompatible-function-pointer-types-strict]
>>          .mode_valid = mdp4_lvds_connector_mode_valid,
>>                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 1 error generated.
> 
> It will be picked into 6.1-rc and then propagate through the stable 
> kernel updates.
> 
> Anyway:
> 
> Fixes: 3e87599b68e7 ("drm/msm/mdp4: add LVDS panel support")
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

Yes, it was already merged to the -fixes tree and a PR with it was sent 
out for 6.1-rc

https://gitlab.freedesktop.org/drm/msm/-/commit/0b33a33bd15d5bab73b87152b220a8d0153a4587

> 
>