From: robk AT cyberway DOT com DOT sg (Rob Kramer)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: DJGPP and Mapping physical memory from a PCI device
Date: Tue, 13 Jun 2000 10:48:04 +0800
Message-ID: <MPG.13b021c16a39c65d98969a@news.cyberway.com.sg>
References: <39417171_1 AT news DOT siscom DOT net>
Organization: Infologic Pte Ltd
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To: djgpp AT delorie DOT com
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In article <39417171_1 AT news DOT siscom DOT net>, cfought AT siscom DOT net says...
>      I work for an engineering firm and we have a shared memory product that
> requires that we be able to map physical memory from a PCI device so that it
> can be accessed by user applications. I was wondering if anyone could tell
> me of a location of some sample programs that demostrate memory mapping with
> DJGPP DPMI calls....Thanks for any help in advance.........

This is a Quick Hack (but it works), so don't comment on the coding style 
please!

Cheers,

	RoB


bool mapMemory (ulong PhysicalAddr, ulong SizeOfRegion,
               int *Selector, ulong *LinearAddress)
{
    __dpmi_meminfo info;

    info.address    = PhysicalAddr;
    info.size       = SizeOfRegion;

    /* Map physical device to linear memory (dpmi 0x800). */
    if (__dpmi_physical_address_mapping (&info) == -1)
        return false;

    ulong       laddress = info.address;

    /* Allocate a LDT descriptor (dpmi 0x0000). */
    int         selector = __dpmi_allocate_ldt_descriptors (1);

    if (selector == -1)
        return false;

    /* Set segment base address in descriptor (dpmi 0x0007). */
    if (__dpmi_set_segment_base_address (selector, laddress) == -1) {
        __dpmi_free_ldt_descriptor (selector);
        return false;
    }

    /* Set segment limit in descriptor (dpmi 0x0008). */
    if (__dpmi_set_segment_limit (selector, SizeOfRegion - 1) == -1) {
        __dpmi_free_ldt_descriptor (selector);
        return false;
    }

    info.address    = laddress;
    info.size       = SizeOfRegion;

    /* Lock segment (dpmi 0x0600). */
    if (__dpmi_lock_linear_region (&info) == -1) {
        __dpmi_free_ldt_descriptor (selector);
        return false;
    }

    *LinearAddress  = laddress;
    *Selector       = selector;

    return true;
}


bool unmapMemory (ulong SizeOfRegion, int selector, ulong LinearAddress)
{
    __dpmi_meminfo      info;		/* DPMI info block */

    info.address    = LinearAddress;
    info.size       = SizeOfRegion;

    /* Unlock segment (dpmi 0x601). */
    if (__dpmi_unlock_linear_region (&info) == -1)
        return false;

    /* Free LDT descriptor (dpmi 0x0001). */
    if (__dpmi_free_ldt_descriptor (selector) == -1)
        return false;

    /* Free mapped region? (DPMI 1.0 function 0x0801) */

    return true;
}