From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shreyansh Jain <shreyansh.jain@nxp.com>
Subject: Re: [PATCH v9 01/25] eal: define macro container_of
Date: Fri, 9 Sep 2016 09:49:06 +0530
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Cc: <hemant.agrawal@nxp.com>, Jan Viktorin <viktorin@rehivetech.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>, <dev@dpdk.org>
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Hi Ferruh,

On Thursday 08 September 2016 07:46 PM, Ferruh Yigit wrote:
> On 9/7/2016 3:07 PM, Shreyansh Jain wrote:
>> Signed-off-by: Jan Viktorin <viktorin@rehivetech.com>
>> Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>
>> ---
>>  lib/librte_eal/common/include/rte_common.h | 21 +++++++++++++++++++++
>>  1 file changed, 21 insertions(+)
>>
>> diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
>> index 332f2a4..c5d94f3 100644
>> --- a/lib/librte_eal/common/include/rte_common.h
>> +++ b/lib/librte_eal/common/include/rte_common.h
>> @@ -322,6 +322,27 @@ rte_bsf32(uint32_t v)
>>  #define offsetof(TYPE, MEMBER)  __builtin_offsetof (TYPE, MEMBER)
>>  #endif
>>
>> +/**
>> + * Return pointer to the wrapping struct instance.
>> + * Example:
>> + *
>> + *  struct wrapper {
>> + *      ...
>> + *      struct child c;
>> + *      ...
>> + *  };
>> + *
>> + *  struct child *x = obtain(...);
>> + *  struct wrapper *w = container_of(x, struct wrapper, c);
>> + *
>> + * Some implementation already have this defined, thus, conditional
>> + * declaration.
>> + */
>> +#ifndef container_of
>> +#define container_of(p, type, member) \
>> +	((type *) (((char *) (p)) - offsetof(type, member)))
>> +#endif
>> +
>>  #define _RTE_STR(x) #x
>>  /** Take a macro value and get a string version of it */
>>  #define RTE_STR(x) _RTE_STR(x)
>>
>
> Some mlx5 files includes dpdk version of container_of first, they
> produce following warning:
>
> In file included from .../dpdk/build/include/rte_mbuf.h:57:0,
>                  from .../dpdk/build/include/rte_ether.h:52,
>                  from .../dpdk/drivers/net/mlx5/mlx5_trigger.c:38:
> /usr/include/infiniband/verbs.h: In function ‘verbs_get_device’:
> ..../dpdk/build/include/rte_common.h:343:14: warning: cast discards
> ‘const’ qualifier from pointer target type [-Wcast-qual]
>   ((type *) (((char *) (p)) - offsetof(type, member)))
>
> The verbs.h version of container_of is same with dpdk one, I am not able
> to find why one gives warning but other not.

Thanks for highlighting. I am setting up my environment and will have a 
look.

>
> Regards,
> ferruh
>
>

-- 
Shreyansh