Messages in this thread | | | Date | Fri, 24 Feb 2023 17:11:11 +0100 | Subject | Re: [PATCH net-next v3 4/5] ip_tunnel: constify input argument of ip_tunnel_info_opts( ) | From | Alexander Lobakin <> |
| |
From: Gavin Li <gavinl@nvidia.com> Date: Mon, 20 Feb 2023 18:42:14 +0800
> > On 2/20/2023 4:46 AM, Simon Horman wrote: >> External email: Use caution opening links or attachments >> >> >> On Sun, Feb 19, 2023 at 09:29:21PM +0100, Simon Horman wrote: >>> On Fri, Feb 17, 2023 at 05:39:24AM +0200, Gavin Li wrote: >>>> Constify input argument(i.e. struct ip_tunnel_info *info) of >>>> ip_tunnel_info_opts( ) so that it wouldn't be needed to W/A it each >>>> time >>>> in each driver. >>>> >>>> Signed-off-by: Gavin Li <gavinl@nvidia.com> >>>> --- >>>> include/net/ip_tunnels.h | 4 ++-- >>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h >>>> index fca357679816..32c77f149c6e 100644 >>>> --- a/include/net/ip_tunnels.h >>>> +++ b/include/net/ip_tunnels.h >>>> @@ -485,9 +485,9 @@ static inline void iptunnel_xmit_stats(struct >>>> net_device *dev, int pkt_len) >>>> } >>>> } >>>> >>>> -static inline void *ip_tunnel_info_opts(struct ip_tunnel_info *info) >>>> +static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info >>>> *info) >>>> { >>>> - return info + 1; >>>> + return (void *)(info + 1); >>> I'm unclear on what problem this is trying to solve, >>> but info being const, and then returning (info +1) >>> as non-const feels like it is masking rather than fixing a problem. >> I now see that an example of the problem is added by path 5/5. >> >> ... >> CC [M] drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.o >> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c: In function >> 'mlx5e_gen_ip_tunnel_header_vxlan': >> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:103:43: >> error: passing argument 1 of 'ip_tunnel_info_opts' discards 'const' >> qualifier from pointer target type [-Werror=discarded-qualifiers] >> 103 | md = ip_tunnel_info_opts(e->tun_info); >> | ~^~~~~~~~~~ >> In file included from >> drivers/net/ethernet/mellanox/mlx5/core/en/tc_tun_vxlan.c:4: >> ./include/net/ip_tunnels.h:488:64: note: expected 'struct >> ip_tunnel_info *' but argument is of type 'const struct ip_tunnel_info *' >> 488 | static inline void *ip_tunnel_info_opts(struct ip_tunnel_info >> *info) >> | >> ~~~~~~~~~~~~~~~~~~~~~~~^~~~ >> ... >> >> But I really do wonder if this patch masks rather than fixes the problem. > Hi Olek, any comment?
Hi,
Sorry for the late reply, was busy at work ._.
I initially proposed a solution via _Generic or __builtin_choose_expr to return const or non-const opts basing on the input pointer type. I don't like simple cast-aways.
See container_of_const() how it dynamically chooses whether to add `const` or not when returning the result.
>> >>>> } >>>> >>>> static inline void ip_tunnel_info_opts_get(void *to, >>>> -- >>>> 2.31.1 >>>>
Thanks, Olek
| |