A QEMU pipe is a very fast communication channel between the
guest system and the emulator. Usage from the guest is simply
something like;

// connect to special device
fd = open("/dev/qemu_pipe", O_RDWR);

// tell which service we want to talk to (must be zero-terminated)
write(fd, "pipeName", strlen("pipeName")+1);

// do read()/write() through fd now
...

// close channel
close(fd);

Signed-off-by: David 'Digit' Turner
[Added support for parameter buffers for speed]
igned-off-by: Xin, Xiaohui
Signed-off-by: Jiang, Yunhong
Signed-off-by: Nakajima, Jun
[Ported to 3.6]
Signed-off-by: Tom Keel
[Ported to 3.7, moved to platform/goldfish]
Signed-off-by: Alan Cox
Signed-off-by: Greg Kroah-Hartman