[openib-general] [PATCH] [RFC] librdmacm: expose device list to users

[Andrew Friedley]

What's the best way to map the ibv_context's return from 
rdma_get_devices() to rdma_cm_id's for use with the rest of the RDMA 
functions?

Should I allocate my own rdma_cm_id and fill it in (like 
rdma_create_id()), or am I missing something?

Andrew

Sean Hefty wrote:
> The following patch adds calls to the userspace RDMA CM to return its list
> of RDMA devices.  The calls are similar to ibv_get_device_list() /
> ibv_free_device_list().
> 
> Currently, RDMA device contexts are handed to the user only after they
> create an rdma_cm_id and bind it to a local device.  By exposing the device
> list to the user, it makes it easier for the user to allocate device
> specific resources (such as PDs, CQs, etc.) that are shared among multiple
> rdma_cm_id's.
> 
> Signed-off-by: Sean Hefty <sean.hefty at intel.com>
> ---
> Index: include/rdma/rdma_cma.h
> ===================================================================
> --- include/rdma/rdma_cma.h	(revision 8215)
> +++ include/rdma/rdma_cma.h	(working copy)
> @@ -332,4 +332,20 @@ static inline uint16_t rdma_get_dst_port
>  		((struct sockaddr_in *) &id->route.addr.dst_addr)->sin_port;
>  }
>  
> +/**
> + * rdma_get_devices - Get list of RDMA devices currently available.
> + * @num_devices: If non-NULL, set to the number of devices returned.
> + *
> + * Return a NULL-terminated array of opened RDMA devices.  Callers can use this
> + * routine to allocate resources on specific RDMA devices that will be shared
> + * across multiple rdma_cm_id's.
> + * The array must be released by calling rdma_free_devices().
> + */
> +struct ibv_context **rdma_get_devices(int *num_devices);
> +
> +/**
> + * rdma_free_devices - Frees the list of devices returned by rdma_get_devices().
> + */
> +void rdma_free_devices(struct ibv_context **list);
> +
>  #endif /* RDMA_CMA_H */
> Index: src/cma.c
> ===================================================================
> --- src/cma.c	(revision 8517)
> +++ src/cma.c	(working copy)
> @@ -216,6 +216,32 @@ err:
>  	return ret;
>  }
>  
> +struct ibv_context **rdma_get_devices(int *num_devices)
> +{
> +	struct ibv_context **devs = NULL;
> +	int i;
> +
> +	if (!cma_dev_cnt && ucma_init())
> +		goto out;
> +
> +	devs = malloc(sizeof *devs * (cma_dev_cnt + 1));
> +	if (!devs)
> +		goto out;
> +
> +	for (i = 0; i < cma_dev_cnt; i++)
> +		devs[i] = cma_dev_array[i].verbs;
> +	devs[i] = NULL;
> +out:
> +	if (num_devices)
> +		*num_devices = devs ? cma_dev_cnt : 0;
> +	return devs;
> +}
> +
> +void rdma_free_devices(struct ibv_context **list)
> +{
> +	free(list);
> +}
> +
>  static void __attribute__((destructor)) rdma_cma_fini(void)
>  {
>  	ucma_cleanup();
> Index: src/librdmacm.map
> ===================================================================
> --- src/librdmacm.map	(revision 8215)
> +++ src/librdmacm.map	(working copy)
> @@ -21,5 +21,7 @@ RDMACM_1.0 {
>  		rdma_get_dst_attr;
>  		rdma_join_multicast;
>  		rdma_leave_multicast;
> +		rdma_get_devices;
> +		rdma_free_devices;
>  	local: *;
>  };
> 
> 
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