> Is there some doc available addressing the problem of
> accessing this above-linux area and using it in both user / kernel space?
To use/access a set-aside region above linux, I put the following in the
linux lilo.conf file:
image=/boot/rtl3.0-2.2.18
append="mem=252M"
label=rtl2218
read-only
root=/dev/hda2
Then you run lilo, and reboot. In a linux user program you then
to set some pointer variables to the physical and virtual above-linux
area. For example:
if ((fd = open("/dev/mem", O_RDWR)) < 0) {
perror("main() opening /dev/mem");
return -1;
}
// Establish a pointer to the reserved memory above linux
pram_above_linux = (void *) (LINUX_MEGS * MEGABYTE);
vram_above_linux = (void *) ((UI32) mmap(0,
(4 * MEGABYTE),
PROT_WRITE | PROT_READ,
MAP_SHARED | MAP_FILE,
fd,
(unsigned int) (pram_above_linux)));
The address space needs to begin on a page boundary. If it doesn't your
user-space program will core dump. I use the following code to insure a
page boundary:
// compute pbar0 4096 boundry
pb = (void *) ((unsigned int) digitizer[dig].pbar0 & 0xfffff000);
// determine the offset from the 4096 boundry
off = (int) digitizer[dig].pbar0 - (int) pb;
digitizer[dig].vbar0 = (void *) ((UI32) mmap(0, 4096, PROT_WRITE |
PROT_READ, MAP_SHARED | MAP_FILE, fd, (unsigned int) pb) + off);
To work with the PCI dma, you will need both physical and virtual pointers
in your code. Us the victuals to access variables programatically, and
the the physical pointers for dma.
-Wayne
-- [rtl] ---
To unsubscribe:
echo "unsubscribe rtl" | mail [EMAIL PROTECTED] OR
echo "unsubscribe rtl <Your_email>" | mail [EMAIL PROTECTED]
--
For more information on Real-Time Linux see:
http://www.rtlinux.org/rtlinux/
