Re: [PATCH] drm: atomic helper: fix W=1 warnings

[Benjamin GAIGNARD <benjamin.gaignard@st.com>]

On 10/4/19 2:27 PM, Ville Syrjälä wrote:
> On Fri, Oct 04, 2019 at 12:48:02PM +0200, Benjamin Gaignard wrote:
>> Le jeu. 3 oct. 2019 à 17:46, Ville Syrjälä
>> <ville.syrjala@linux.intel.com> a écrit :
>>> On Thu, Oct 03, 2019 at 05:37:15PM +0200, Benjamin Gaignard wrote:
>>>> Le jeu. 3 oct. 2019 à 17:05, Ville Syrjälä
>>>> <ville.syrjala@linux.intel.com> a écrit :
>>>>> On Thu, Oct 03, 2019 at 04:46:54PM +0200, Benjamin Gaignard wrote:
>>>>>> Le jeu. 3 oct. 2019 à 16:27, Ville Syrjälä
>>>>>> <ville.syrjala@linux.intel.com> a écrit :
>>>>>>> On Mon, Sep 09, 2019 at 03:52:05PM +0200, Benjamin Gaignard wrote:
>>>>>>>> Fix warnings with W=1.
>>>>>>>> Few for_each macro set variables that are never used later.
>>>>>>>> Prevent warning by marking these variables as __maybe_unused.
>>>>>>>>
>>>>>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
>>>>>>>> ---
>>>>>>>>   drivers/gpu/drm/drm_atomic_helper.c | 36 ++++++++++++++++++------------------
>>>>>>>>   1 file changed, 18 insertions(+), 18 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
>>>>>>>> index aa16ea17ff9b..b69d17b0b9bd 100644
>>>>>>>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>>>>>>>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>>>>>>>> @@ -262,7 +262,7 @@ steal_encoder(struct drm_atomic_state *state,
>>>>>>>>              struct drm_encoder *encoder)
>>>>>>>>   {
>>>>>>>>        struct drm_crtc_state *crtc_state;
>>>>>>>> -     struct drm_connector *connector;
>>>>>>>> +     struct drm_connector __maybe_unused *connector;
>>>>>>> Rather ugly. IMO would be nicer if we could hide something inside
>>>>>>> the iterator macros to suppress the warning.
>>>>>> Ok but how ?
>>>>>> connector is assigned in the macros but not used later and we can't
>>>>>> set "__maybe_unused"
>>>>>> in the macro.
>>>>>> Does another keyword exist for that ?
>>>>> Stick a (void)(connector) into the macro?
>>>> That could work but it will look strange inside the macro.
>>>>
>>>>> Another (arguably cleaner) idea would be to remove the connector/crtc/plane
>>>>> argument from the iterators entirely since it's redundant, and instead just
>>>>> extract it from the appropriate new/old state as needed.
>>>>>
>>>>> We could then also add a for_each_connector_in_state()/etc. which omit
>>>>> s the state arguments and just has the connector argument, for cases where
>>>>> you don't care about the states when iterating.
>>>> That may lead to get a macro for each possible combination of used variables.
>>> We already have new/old/oldnew, so would "just" add one more.
>> Not just one, it will be one each new/old/oldnew macro to be able to distinguish
>> when connector is used or not.
> What I'm suggesting is this:
> for_each_connector_in_state(state, connector, i)
> for_each_old_connector_in_state(state, old_conn_state, i)
> for_each_new_connector_in_state(state, new_conn_state, i)
> for_each_oldnew_connector_in_state(state, old_conn_state, new_conn_state, i)
>
> So only four in total for each object type, instead of the current
> three.

You are missing these cases: old and connector, new and connector,

old and new and connector are needed together.

>