Very Computer

I have just tripped over the above manual page, which comments that:

       "Since this function  is  not  implemented  as  of
       Linux  0.99.11,  it will always return -1 and set errno to
       ENOSYS."

Can anyone tell me what happened to phys [like was it ever implemented,
and if so where is it now?], or give me any pointers to other ways of
accessing physical memory from outside the kernel. (I need to write to
and read from a PCI device without the delay associated with the context
switch in and out ofthe kernel)

----------------------------------------------------------------------
Andrew Hoddinott                    Advanced Rendering Technology Ltd.
Software Engineer               Mount Pleasant House, 2 Mount Pleasant

http://www.art.co.uk/                 Tel. +44 1223 563854 Fax. 516520
PGP key fingerprint:  F1 AA FF 2E 61 7C 68 A8  C0 65 0A BC 52 65 69 0C

Quote:> Can anyone tell me what happened to phys [like was it ever implemented,
> and if so where is it now?], or give me any pointers to other ways of
> accessing physical memory from outside the kernel. (I need to write to
> and read from a PCI device without the delay associated with the context
> switch in and out ofthe kernel)

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

void *
mapPhysical(void *phys, unsigned length, void *virt, int writable) {
    // ensure that the addresses are page-aligned,
    // and length is a page-multiple.
    int fd = open("/dev/kmem",(writable?O_RDWR:O_RDONLY));
    if (fd == -1) {
        perror("open failed");
        return (void*) -1;
    }
    return mmap(virt,
                length,
                PROT_READ | (writable?PROT_WRITE:0),
                MAP_PRIVATE | MAP_FILE | (virt?MAP_FIXED:0),
                fd,
                (off_t)phys);

Quote:}

    if (screen == (void*)-1) {
        perror("map failed");
        return 1;
    }
    for (unsigned i=0; i<len/2; i++)
        putchar(screen[i] & 0x00ffU);
    return 0;

Quote:}

regards, mark hahn.
--

                                        http://neurocog.lrdc.pitt.edu/~hahn/

If you need to access io port space look at the call
to ioperm (and read the IO-Port-Programming mini howto).

If you want to access a memory-mapped device you can open
"/dev/mem" and use mmap to map the physical addressees to the
address space of your process.

For both cases you may have to run the program with root
permissions.

Itai
--