mmap() vs. character special file


Hello!

mmap(2) manpage has the following title:

NAME
mmap -- allocate memory, or map files or devices into memory

I'm curious about mmap()ing devices (particularly, HDD slices). The manpage
mentions character special files only once:

[EINVAL] MAP_ANON has not been specified and fd did not refer-
ence a regular or character special file.

So it looks like one should be able to mmap() a character special file (w/o MAP_ANON, of course). However, if I try to issue:

if ((fd=open(argv[1], O_RDWR)) == -1)
err(EX_NOINPUT, "Can't open %s for readind and writing", argv[1]);

if ((diskp=mmap(NULL, label_offset + sizeof (struct disklabel),
PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0)) == MAP_FAILED)
err(EX_IOERR, "Can't mmap() file");

against /dev/adXsY (adXsY and adXsYZ are _not_ mounted), I'm getting EINVAL
from mmap(). Is mmap()ping a disk slice/partition impossible by design, or it
just isn't implemented yet? IMHO manpage doesn't reply to this question.

Sincerely, Dmitry
--
Atlantis ISP, System Administrator
e-mail: dmitry@xxxxxxxxxxxxxx
nic-hdl: LYNX-RIPE
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