--- (pts/2) mmondor@sat.xisop $ apropos aio 
aio_cancel (3) - cancel an outstanding asynchronous I/O operation (REALTIME)
aio_cancel — cancel an outstanding asynchronous I/O operation (REALTIME)
aio_error (3) - retrieve error status of asynchronous I/O operation (REALTIME)
aio_error — retrieve error status of asynchronous I/O operation (REAL‐ TIME)
aio_fsync (3) - asynchronous data synchronization of file (REALTIME)
aio_fsync — asynchronous data synchronization of file (REALTIME)
aio_read (3) - asynchronous read from a file (REALTIME)
aio_read — asynchronous read from a file (REALTIME)
aio_return (3) - retrieve return status of asynchronous I/O operation (REALTIME)
aio_return — retrieve return status of asynchronous I/O operation (REAL‐ TIME)
aio_suspend (3) - suspend until asynchronous I/O operations or timeout complete (REALTIME)
aio_suspend — suspend until asynchronous I/O operations or timeout com‐ plete (REALTIME)
aio_write (3) - asynchronous write to a file (REALTIME)
aio_write — asynchronous write to a file (REALTIME)

in man siginfo:

     SI_ASYNCIO  The signal was generated by completion of an asynchronous I/O
                 operation.  The siginfo structure contains the following
                 additional members:

                       int si_fd;
                       long si_band;

                 The si_fd argument contains the file descriptor number on
                 which the operation was completed and the si_band field con‐
                 tains the side and priority of the operation.  If the opera‐
                 tion was a normal read, si_band will contain POLLIN |
                 POLLRDNORM; on an out‐of‐band read it will contain POLLPRI |
                 POLLRDBAND; on a normal write it will contain POLLOUT |
                 POLLWRNORM; on an out‐of‐band write it will contain POLLPRI |
                 POLLWRBAND.