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SubjectRe: [PATCH][next] Input: Fix fall-through warning for Clang
On Mon, Jun 14, 2021 at 03:12:31PM -0700, Dmitry Torokhov wrote:
> Hi Joe,
>
> On Mon, Jun 07, 2021 at 03:02:40PM -0700, Joe Perches wrote:
> > On Mon, 2021-06-07 at 16:48 -0500, Gustavo A. R. Silva wrote:
> > > In preparation to enable -Wimplicit-fallthrough for Clang, fix a
> > > warning by explicitly adding a fallthrough; statement.
> > []
> > > diff --git a/drivers/input/joystick/sidewinder.c b/drivers/input/joystick/sidewinder.c
> > []
> > > @@ -660,6 +660,7 @@ static int sw_connect(struct gameport *gameport, struct gameport_driver *drv)
> > >   fallthrough;
> > >   case 45: /* Ambiguous packet length */
> > >   if (j <= 40) { /* ID length less or eq 40 -> FSP */
> > > + fallthrough;
> > >   case 43:
> > >   sw->type = SW_ID_FSP;
> > >   break;
> >
> > Yuck. Super ugly. There's no need to play games with indentation.
>
> Yeah, the original code is not pretty :(

Isn't this a Duff device for performance[1]?

In which case it might be better not to modify it and just go
with the fallthrough marking?

Another similar case can be found at
drivers/scsi/aic94xx/aic94xx_sds.c:714:

714 static void *asd_find_ll_by_id(void * const start, const u8 id0, const u8 id1)
715 {
716 struct asd_ll_el *el = start;
717
718 do {
719 switch (id1) {
720 default:
721 if (el->id1 == id1)
722 case 0xFF:
723 if (el->id0 == id0)
724 return el;
725 }
726 el = start + le16_to_cpu(el->next);
727 } while (el != start);
728
729 return NULL;
730 }

--
Gustavo

[1] https://www.drdobbs.com/a-reusable-duff-device/184406208

>
> >
> > Perhaps the simpler:
> >
> > case 43:
> > sw->type = SW_ID_FSP;
> > break;
> > case 45: /* Ambiguous packet length */
> > if (j <= 40) { /* ID length less or eq 40 -> FSP */
> > sw->type = SW_ID_FSP;
> > break;
> > }
> > sw->number++;
> > fallthrough;
> >
> >
>
> Could you resubmit this version properly formatted?
>
> Thanks.
>
> --
> Dmitry

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