linux-kernel - Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion

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Date:   Mon, 24 Sep 2018 15:27:37 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     dledford@...hat.com, jgg@...pe.ca, linux-rdma@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] IB/mlx4: Avoid implicit enumerated type conversion

On Mon, Sep 24, 2018 at 03:24:36PM -0700, Nick Desaulniers wrote:
> On Mon, Sep 24, 2018 at 12:57 PM Nathan Chancellor
> <natechancellor@...il.com> wrote:
> >
> > Clang warns when one enumerated type is implicitly converted to another.
> >
> > drivers/infiniband/hw/mlx4/mad.c:1811:41: warning: implicit conversion
> > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration
> > type 'enum ib_qp_create_flags' [-Wenum-conversion]
> >                 qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_TUNNEL_QP;
> >                                                     ~ ^~~~~~~~~~~~~~~~~~~~~~~
> >
> > drivers/infiniband/hw/mlx4/mad.c:1819:41: warning: implicit conversion
> > from enumeration type 'enum mlx4_ib_qp_flags' to different enumeration
> > type 'enum ib_qp_create_flags' [-Wenum-conversion]
> >                 qp_init_attr.init_attr.create_flags = MLX4_IB_SRIOV_SQP;
> >                                                     ~ ^~~~~~~~~~~~~~~~~
> >
> > The type mlx4_ib_qp_flags explicitly provides supplemental values to the
> > type ib_qp_create_flags. Make that clear to Clang by changing the
> > create_flags type to u32.
> >
> > Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >  include/rdma/ib_verbs.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> > index e463d3007a35..f6f4d9e3c8ed 100644
> > --- a/include/rdma/ib_verbs.h
> > +++ b/include/rdma/ib_verbs.h
> > @@ -1149,7 +1149,7 @@ struct ib_qp_init_attr {
> >         struct ib_qp_cap        cap;
> >         enum ib_sig_type        sq_sig_type;
> >         enum ib_qp_type         qp_type;
> > -       enum ib_qp_create_flags create_flags;
> > +       u32                     create_flags;
> 
> I think it might be better to just have explicit casts at the
> assignment.  What do the maintainers think?
> 

That's fine with me, I tend to explicitly cast if it is only one
location but it certainly makes sense in this case as well. I'll
wait for the maintainers to weigh in before sending a v2.

Thanks for the review,
Nathan

> >
> >         /*
> >          * Only needed for special QP types, or when using the RW API.
> > --
> > 2.19.0
> >
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers