ibv_alloc_dmah(3)       Libibverbs Programmer's Manual       ibv_alloc_dmah(3)

NAME
       ibv_alloc_dmah - allocate a dma handle

       int ibv_dealloc_dmah - deallocate a dma handle

SYNOPSIS
              #include <infiniband/verbs.h>

              struct ibv_dmah *ibv_alloc_dmah(struct ibv_context *context, struct ibv_dmah_init_attr *attr);

              int ibv_dealloc_dmah(struct ibv_dmah *dmah);

DESCRIPTION
       ibv_alloc_dmah() allocates an ibv_dmah object that is associated with
       the given context and the input attr parameter.

       The allocated handle can be later used for optimizing DMA and RDMA
       operations associated with a registered memory region.

       Once the ibv_dmah usage has been ended ibv_dealloc_dmah() should be
       called.

       This call will release resources that were earlier allocated using the
       ibv_alloc_dmah() API.

ARGUMENTS
   attr

              enum ibv_tph_mem_type {
                  IBV_TPH_MEM_TYPE_VM, /* volatile memory */
                  IBV_TPH_MEM_TYPE_PM, /* persistent memory */
              };

              enum ibv_dmah_init_attr_mask {
                  IBV_DMAH_INIT_ATTR_MASK_CPU_ID = 1 << 0,
                  IBV_DMAH_INIT_ATTR_MASK_PH = 1 << 1,
                  IBV_DMAH_INIT_ATTR_MASK_TPH_MEM_TYPE = 1 << 2,
              };

              struct ibv_dmah_init_attr {
                  uint32_t comp_mask; /* From ibv_dmah_init_attr_mask */
                  uint32_t cpu_id;
                  uint8_t ph;
                  uint8_t tph_mem_type; /* From enum ibv_tph_mem_type */
              };

       comp_mask
              Bitmask specifying what fields in the structure are valid.

       cpu_id The cpu id that the dma handle refers to.

       ph     Processing hints, used to aid in optimizing the handling of
              transactions over PCIe.

       tph_mem_type
              The target memory type, one among enum ibv_tph_mem_type.

RETURN VALUE
       ibv_alloc_dmah() returns a pointer to the allocated dma handle object,
       or NULL if the request fails.

       ibv_dealloc_dmah() returns 0 upon success, otherwise the errno value.

SEE ALSO
       ibv_reg_mr_ex(3)

AUTHOR
       Yishai Hadas <yishaih@nvidia.com>

libibverbs                         2025-5-8                  ibv_alloc_dmah(3)