NAME

       umad_recv - receive umad

SYNOPSIS

       #include <infiniband/umad.h>

       int umad_recv(int portid, void *umad, int *length, int timeout_ms);

DESCRIPTION

       umad_recv()  waits up to timeout_ms milliseconds for an incoming MAD message to be received from the port
       specified by portid.

       A MAD "message" consists of a single MAD packet or a coalesced multipacket  RMPP  transmission.   In  the
       RMPP case the header of the first RMPP packet is returned as the header of the buffer and the buffer data
       contains the coalesced data section of each subsequent RMPP MAD packet within the transmission.  Thus all
       the RMPP headers except the first are not copied to user space from the kernel.

       The  message  is  copied  to  the  umad  buffer  if  there  is sufficient room and the received length is
       indicated.  If the buffer is not large enough, the size of the umad buffer needed is returned in  length.
       A negative timeout_ms makes the function block until a packet is received. A timeout_ms parameter of zero
       indicates a non blocking read.

       Note length is a pointer to the length of the data portion of the umad buffer.  This means that umad must
       point to a buffer at least umad_size() + *length bytes long.

       Note  also  that *length must be >= 256 bytes.  This length allows for at least a single MAD packet to be
       returned.

RETURN VALUE

       umad_recv() on success return the agentid; on error, errno is set and a negative  value  is  returned  as
       follows:
        -EINVAL      invalid port handle or agentid or *length is less than the minimum supported
        -EIO         receive operation failed
        -EWOULDBLOCK non blocking read can't be fulfilled
        -ENOSPC      The provided buffer is not long enough for the complete message.

SEE ALSO

       umad_poll(3)

AUTHOR

       Hal Rosenstock <halr@voltaire.com>