Re: [PATCH] drm/amdgpu/display: add fallthrough comment

[Alex Deucher <alexdeucher@xxxxxxxxx>]

On Thu, Dec 5, 2019 at 5:10 PM Liu, Zhan <Zhan.Liu@xxxxxxx> wrote:
>
>
>
> > -----Original Message-----
> > From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Alex
> > Deucher
> > Sent: 2019/December/05, Thursday 4:39 PM
> > To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>
> > Subject: [PATCH] drm/amdgpu/display: add fallthrough comment
> >
> > To avoid a compiler warning.
> >
> > Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> > ---
> >  drivers/gpu/drm/amd/display/dc/dce/dce_aux.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> > b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> > index 191b68b8163a..f1a5d2c6aa37 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> > +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_aux.c
> > @@ -645,6 +645,7 @@ bool dce_aux_transfer_with_retries(struct
> > ddc_service *ddc,
> >                       case AUX_TRANSACTION_REPLY_AUX_DEFER:
> >                       case
> > AUX_TRANSACTION_REPLY_I2C_OVER_AUX_DEFER:
> >                               retry_on_defer = true;
> > +                             /* fall through */
>
> I am a bit confusing here. Why a comment can avoid a compiler warning?

The kernel enables fall through warnings, so unless there is a comment
mentioning that are are expecting to fall through here, we get a
warning.  The idea is to find missing breaks in switch code.

Alex

>
> >                       case
> > AUX_TRANSACTION_REPLY_I2C_OVER_AUX_NACK:
> >                               if (++aux_defer_retries >=
> > AUX_MAX_DEFER_RETRIES) {
> >                                       goto fail;
> > --
> > 2.23.0
> >
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