I've just been looking at src/sys/dev/ata/ata_wdc.c (and a few other
files) which, at the top has:

#ifndef __BUS_SPACE_HAS_STREAM_METHODS
#define    bus_space_write_multi_stream_2    bus_space_write_multi_2
#define    bus_space_write_multi_stream_4    bus_space_write_multi_4
#define    bus_space_read_multi_stream_2    bus_space_read_multi_2
#define    bus_space_read_multi_stream_4    bus_space_read_multi_4
#endif /* __BUS_SPACE_HAS_STREAM_METHODS */

bus_space_read/write_multi_stream_2/4 is new to me, so I went digging
around some and found in arch/prep/include/bus.h:

/* 
 *      void bus_space_read_multi_stream_N __P((bus_space_tag_t tag,
 *          bus_space_handle_t bsh, bus_size_t offset,
 *          u_intN_t *addr, size_t count));
 *
 * Read `count' 2, 4, or 8 byte stream quantities from bus space
 * described by tag/handle/offset and copy into buffer provided.
 */

My question has now become, what is a "stream quantity"?  Are
these functions redundant with the bus_space_read/write_multi_N?
Why aren't these functions documented at all in bus_space(9)?

-allen