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SubjectRe: [PATCH] iio: accel: cros_ec_accel_legacy: Mark expected switch fall-throughs
On Sat, 18 Aug 2018 17:34:40 +0200
Marcus Folkesson <marcus.folkesson@gmail.com> wrote:

> Hi Gutavo,
>
> Sorry for the delay.
>
> On Wed, Aug 15, 2018 at 12:50:10PM -0500, Gustavo A. R. Silva wrote:
> > Hi Marcus,
> >
> > On 8/15/18 12:27 PM, Marcus Folkesson wrote:
> > > Hi,
> > >
> > > On Wed, Aug 15, 2018 at 11:38:52AM -0500, Gustavo A. R. Silva wrote:
> > >> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> > >> where we are expecting to fall through.
> > >>
> > >> Addresses-Coverity-ID: 1462408 ("Missing break in switch")
> > >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> > >> ---
> > >> drivers/iio/accel/cros_ec_accel_legacy.c | 2 ++
> > >> 1 file changed, 2 insertions(+)
> > >>
> > >> diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
> > >> index 063e89e..d609654 100644
> > >> --- a/drivers/iio/accel/cros_ec_accel_legacy.c
> > >> +++ b/drivers/iio/accel/cros_ec_accel_legacy.c
> > >> @@ -385,8 +385,10 @@ static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
> > >> switch (i) {
> > >> case X:
> > >> ec_accel_channels[X].scan_index = Y;
> > >> + /* fall through */
> > >> case Y:
> > >> ec_accel_channels[Y].scan_index = X;
> > >> + /* fall through */
> > >> case Z:
> > >> ec_accel_channels[Z].scan_index = Z;
> > >> }
> > >
> > > Hum, I'm not sure we are supposed to fall through here, even if it does
> > > not hurt to do so.
> >
> > Yeah. You're right. It doesn't hurt but is actually redundant. I think
> > the original intention was to break instead of falling through.
> >
> > > I even think we can remove the switch and put that outside the for-loop,
> > > e.g:
> > >
> > > ec_accel_channels[X].scan_index = Y;
> > > ec_accel_channels[Y].scan_index = X;
> > > ec_accel_channels[Z].scan_index = Z;
> > >
> > > for (i = X ; i < MAX_AXIS; i++) {
> > > if (state->sensor_num == MOTIONSENSE_LOC_LID && i != Y)
> > > state->sign[i] = -1;
> > > else
> > > state->sign[i] = 1;
> > > }
> > >
> >
> > I like this, but the code clearly depends on MAX_AXIS. So, if MAX_AXIS
> > will be always 3, then the change you suggest is just fine. Otherwise,
> > it seems that adding a break to each case is the right way to go.
> >
> > What do you think?
>
> Well, I guess it is a matter of taste after all.
> I don't think the number of axis will change, but just put the break in
> place is good enough.
>
> Anyway, If we choose to not use the switch, I think we should remove the
> for-loop as well, eg:
>
> ec_accel_channels[X].scan_index = Y;
> ec_accel_channels[Y].scan_index = X;
> ec_accel_channels[Z].scan_index = Z;
>
> if (state->sensor_num == MOTIONSENSE_LOC_LID) {
> state->sign[X] = -1;
> state->sign[Y] = 1;
> state->sign[Z] = -1;
> } else {
> state->sign[X] = 1;
> state->sign[Y] = 1;
> state->sign[Z] = 1;
> }
>
> But someone else may like to give their point of view on this change.

Looks like the right tidy up to me. The original code was 'novel' :)

Jonathan
>
> >
> > Thanks for the feedback.
> > --
> > Gustavo
>
> Best regards
> Marcus Folkesson

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