Very Computer

Help.....! I'm still trying to get my DMA to work so I need to get the
actual phy mem address. The VDS method is preferable to copying data into a
buffer below the 1M mark and dmaing that because speed is a factor. What's
wrong with my code (or right with it)........I always get some sort of
error code back...often in reserved registers...please help!

struct DMA_DESCR_STR {
        DWORD size;
        DWORD offset;
        WORD segsel;
        WORD buffID;
        DWORD phy_addr;

Quote:};

DWORD get_phy_addr(     DWORD offset_addr, DWORD size )
{
        DWORD dds_addr;
        struct DMA_DESCR_STR dds;
        __dpmi_regs InRegs;

        //check for VDS at bit 5 of mem 0x0040:007b  ----   HOW CAN I CHECK THIS
BIT????

        dds.size = size;
        dds.segsel = (WORD)_my_ds();                                    //returns an int
        dds.offset = offset_addr ;

        // lock dma region -  Clear register structure */
        memset( &InRegs, 0, sizeof( __dpmi_regs ) );

        InRegs.h.ah = 0x81 ;
        InRegs.h.al = 0x03 ;    //specifies VDS lock dma region
        InRegs.x.dx = 0x3c ;    // do remap and don't allocate buffer

        dds_addr = (DWORD)&dds;
        InRegs.x.es =(WORD)(dds_addr >> 16);                              // upper 16 bits
        InRegs.x.di = (WORD)((DWORD)0xffff & dds_addr);             // lower 16 bits

        if ((__dpmi_int (0x4b, &InRegs)) == -1) {
                printf("get_phy_addr : dpmi_int error...");
                return 0;
        }
        if (InRegs.x.flags & 1) {      /* is carry flag set?  */
                printf("\nget_phy_addr - Call to VDS lock dma region failed...\n");
                printf("Error Code AL = %x\n",InRegs.h.al);
                return ( FALSE );
        } else {
                return dds.phy_addr;
        }

Quote:}                      

Thanks!!!

--

Dept. of Engineering
Durham University
United Kingdom

James Deuchar schrieb in Nachricht

Quote:>Help.....! I'm still trying to get my DMA to work so I need to get the
>actual phy mem address. The VDS method is preferable to copying data into a
>buffer below the 1M mark and dmaing that because speed is a factor. What's
>wrong with my code (or right with it)........I always get some sort of
>error code back...often in reserved registers...please help!

I had the same problem. I couldn't get VDS to return the physical address of
a malloc'd buffer (not coninuous or so), allocating one with VDS didn't work
either,
I needed a buffer of about 2MB which was too big for VDS.
Then the problem was that it worked under plain DOS but not in a W95 DOS
box.

Then someone told me I should use XMS, which solved my problems.
Allocate your buffer with XMS use the XMS lock handle function to get the
physical
address. Then you can either build a selector for that physical address or
use
the XMS moving functions to access that buffer.

Quote:> //check for VDS at bit 5 of mem 0x0040:007b  ----   HOW CAN I CHECK THIS
>BIT????

That would be something like
  _farpeekb(__dos_ds, 0x4007) & 0x20

good luck!

Peter Remmers