NAME

       io_uring_prep_read_fixed - prepare I/O read request with registered buffer

SYNOPSIS

       #include <liburing.h>

       void io_uring_prep_read_fixed(struct io_uring_sqe *sqe,
                               int fd,
                               void *buf,
                               unsigned nbytes,
                               __u64 offset,
                               int buf_index);

DESCRIPTION

       The  io_uring_prep_read_fixed(3)  prepares an IO read request with a previously registered
       IO buffer. The submission queue entry sqe is setup to use the file descriptor fd to  start
       reading  nbytes  into the buffer buf at the specified offset, and with the buffer matching
       the registered index of buf_index.

       This works just like io_uring_prep_read(3) except it requires the use of buffers that have
       been registered with io_uring_register_buffers(3).  The buf and nbytes arguments must fall
       within a region specified by buf_index in the previously  registered  buffer.  The  buffer
       need not be aligned with the start of the registered buffer.

       After the read has been prepared it can be submitted with one of the submit functions.

RETURN VALUE

       None

ERRORS

       The  CQE  res field will contain the result of the operation. See the related man page for
       details on possible values. Note that where synchronous system calls  will  return  -1  on
       failure  and  set  errno to the actual error value, io_uring never uses errno.  Instead it
       returns the negated errno directly in the CQE res field.

SEE ALSO

       io_uring_prep_read(3), io_uring_register_buffers(3)