小贝子编程

如何在DOS扩展器或DPMI环境下进行DMA传输



程序在DOS扩展器+DPMI环境下运行时，如何使用DMA传输？

我的意思是，我们如何分配并获得分配的dma缓冲区的物理地址，以便将该物理地址提供给dma控制器或PCI总线主设备。

有两种可能性：

DOS扩展器或DPMI服务器/主机支持虚拟内存。例如堤道。

DOS扩展器或DPMI服务器/主机不支持虚拟内存，但启用了分页。例如DOS32a。

我正在使用Open Watcom C编译器。

运行时环境为：

FreeDOS+XMS（无EMS/EMM386）+DOS扩展器（DOS32a）

对于DJGPP，解决方案在这里

但最后提到的解决方案（即通过XMS）也能与DOS32a一起使用吗？

DOS32a文档说，在切换到保护模式之前，它会分配所有可用的扩展内存，然后我们的程序可以通过DPMI功能501h分配该内存。

注意：dma缓冲区可以是1MB左右，所以我不能使用传统的内存。

对于干净的DPMI解决方案，您可能需要探索以下DPMI功能（摘录自Ralf Brown的中断列表）：

INT 31 P - DPMI 1.0+ - MAP DEVICE IN MEMORY BLOCK
        AX = 0508h
        ESI = memory block handle
        EBX = page-aligned offset within memory block of page(s) to be mapped
        ECX = number of pages to map
        EDX = page-aligned physical address of device
Return: CF clear if successful
        CF set on error
            AX = error code (8001h,8003h,8023h,8025h) (see #03143)
Notes:  only supported by 32-bit DPMI hosts, but may be used by 16-bit clients
        support of this function is optional; hosts are also allowed to support
          the function for some devices but not others
INT 31 P - DPMI 1.0+ - MAP CONVENTIONAL MEMORY IN MEMORY BLOCK
        AX = 0509h
        ESI = memory block handle
        EBX = page-aligned offset within memory block of page(s) to map
        ECX = number of pages to map
        EDX = page-aligned linear address of conventional (below 1M) memory
Return: CF clear if successful
        CF set on error
            AX = error code (8001h,8003h,8023h,8025h) (see #03143)
Notes:  only supported by 32-bit DPMI hosts, but may be used by 16-bit clients
        support of this function is optional
INT 31 P - DPMI 0.9+ - PHYSICAL ADDRESS MAPPING
        AX = 0800h
        BX:CX = physical address (should be above 1 MB)
        SI:DI = size in bytes
Return: CF clear if successful
            BX:CX = linear address which maps the requested physical memory
        CF set on error
            AX = error code (DPMI 1.0+) (8003h,8021h) (see #03143)
Notes:  implementations may refuse this call because it can circumvent protects
        the caller must build an appropriate selector for the memory
        do not use for memory mapped in the first megabyte

如果以上两项都不允许您将虚拟地址映射到物理地址，也不允许您获得已分配块的物理地址（例如，不受支持），则您需要查看DPMI主机的实现细节（例如，如果它不启用页面转换或可以关闭，则所有地址都是物理地址）。

EDIT：看起来您应该能够分配内存（超过1MB）并获取其物理和虚拟地址。首先，使用XMS/Himem.sys分配并锁定它。这会给你物理地址。接下来，使用DPMI函数0x800获取相应的虚拟地址。

以下是如何（忽略16位版本（使用Borland/Turbo C/C++编译），它仅用于验证XMS例程）：

// file: dma.c
//
// Compiling with Open Watcom C/C++ and DOS/32 DOS extender/DPMI host:
//   wcl386.exe /q /we /wx /bcl=dos4g dma.c
//   sb.exe /b /bndmados32.exe dma.exe
// Before running dmados32.exe do "set DOS32A=/EXTMEM:4096"
// to limit the amount of extended (XMS) memory allocated by DOS/32
// at program start (by default it allocates everything).
//
// Compiling with 16-bit Borland/Turbo C/C++:
//   tcc.exe dma.c
#include <stdio.h>
#include <string.h>
#include <dos.h>
#include <limits.h>
#if defined(__WATCOMC__)
#if !defined(__386__)
#error unsupported target, must be 32-bit (DPMI) DOS app
#endif
#elif defined(__TURBOC__)
#if !defined(__SMALL__)
#error unsupported target, must be 16-bit DOS app with small memory model
#endif
#else
#error unsupported compiler
#endif
typedef unsigned uint;
typedef unsigned long ulong;
typedef signed char int8;
typedef unsigned char uint8;
typedef short int16;
typedef unsigned short uint16;
#if UINT_MIN >= 0xFFFFFFFF
typedef int int32;
typedef unsigned uint32;
#else
typedef long int32;
typedef unsigned long uint32;
#endif
#pragma pack(push, 1)
typedef struct tDpmiRmInt
{
  uint32 edi, esi, ebp, resz0, ebx, edx, ecx, eax;
  uint16 flags, es, ds, fs, gs, ip, cs, sp, ss;
} tDpmiRmInt;
#pragma pack(pop)
int RmInt(uint8 IntNumber, tDpmiRmInt* pRegs)
{
#if defined(__WATCOMC__)
  union REGS inregs, outregs;
  memset(&inregs, 0, sizeof(inregs));
  memset(&outregs, 0, sizeof(outregs));
  inregs.w.ax = 0x300;
  inregs.h.bl = IntNumber;
  inregs.h.bh = 0;
  inregs.w.cx = 0;
  inregs.x.edi = (uint32)pRegs;
  return int386(0x31, &inregs, &outregs);
#elif defined(__TURBOC__)
  struct REGPACK regs;
  memset(&regs, 0, sizeof(regs));
  regs.r_ax = (uint16)pRegs->eax;
  regs.r_bx = (uint16)pRegs->ebx;
  regs.r_cx = (uint16)pRegs->ecx;
  regs.r_dx = (uint16)pRegs->edx;
  regs.r_si = (uint16)pRegs->esi;
  regs.r_di = (uint16)pRegs->edi;
  regs.r_bp = (uint16)pRegs->ebp;
  regs.r_flags = pRegs->flags;
  regs.r_ds = pRegs->ds;
  regs.r_es = pRegs->es;
  // No fs, gs (16-bit code)
  // No ss:sp, cs:ip (int*()/intr() functions set the right values)
  intr(IntNumber, &regs);
  memset(pRegs, 0, sizeof(*pRegs));
  pRegs->eax = regs.r_ax;
  pRegs->ebx = regs.r_bx;
  pRegs->ecx = regs.r_cx;
  pRegs->edx = regs.r_dx;
  pRegs->esi = regs.r_si;
  pRegs->edi = regs.r_di;
  pRegs->ebp = regs.r_bp;
  pRegs->flags = regs.r_flags;
  pRegs->ds = regs.r_ds;
  pRegs->es = regs.r_es;
  return regs.r_ax;
#endif
}
int RmFarCall(tDpmiRmInt* pRegs)
{
#if defined(__WATCOMC__)
  union REGS inregs, outregs;
  memset(&inregs, 0, sizeof(inregs));
  memset(&outregs, 0, sizeof(outregs));
  inregs.w.ax = 0x301;
  inregs.h.bh = 0;
  inregs.w.cx = 0;
  inregs.x.edi = (uint32)pRegs;
  return int386(0x31, &inregs, &outregs);
#elif defined(__TURBOC__)
  uint8 code[128];
  uint8* p = code;
  void far* codef = &code[0];
  void (far* f)(void) = (void(far*)(void))codef;
  *p++ = 0x60;                                                            // pusha
  *p++ = 0x1E;                                                            // push  ds
  *p++ = 0x06;                                                            // push  es
  *p++ = 0x68; *p++ = (uint8)pRegs->ds; *p++ = (uint8)(pRegs->ds >> 8);   // push #
  *p++ = 0x1F;                                                            // pop  ds
  *p++ = 0x68; *p++ = (uint8)pRegs->es; *p++ = (uint8)(pRegs->es >> 8);   // push #
  *p++ = 0x07;                                                            // pop  es
  *p++ = 0xb8; *p++ = (uint8)pRegs->eax; *p++ = (uint8)(pRegs->eax >> 8); // mov ax, #
  *p++ = 0xbb; *p++ = (uint8)pRegs->ebx; *p++ = (uint8)(pRegs->ebx >> 8); // mov bx, #
  *p++ = 0xb9; *p++ = (uint8)pRegs->ecx; *p++ = (uint8)(pRegs->ecx >> 8); // mov cx, #
  *p++ = 0xba; *p++ = (uint8)pRegs->edx; *p++ = (uint8)(pRegs->edx >> 8); // mov dx, #
  *p++ = 0xbe; *p++ = (uint8)pRegs->esi; *p++ = (uint8)(pRegs->esi >> 8); // mov si, #
  *p++ = 0xbf; *p++ = (uint8)pRegs->edi; *p++ = (uint8)(pRegs->edi >> 8); // mov di, #
  *p++ = 0xbd; *p++ = (uint8)pRegs->ebp; *p++ = (uint8)(pRegs->ebp >> 8); // mov bp, #
  *p++ = 0x9A; *p++ = (uint8)pRegs->ip; *p++ = (uint8)(pRegs->ip >> 8);
               *p++ = (uint8)pRegs->cs; *p++ = (uint8)(pRegs->cs >> 8);   // call far seg:offs
  *p++ = 0x60;                                                            // pusha
  *p++ = 0x1E;                                                            // push  ds
  *p++ = 0x06;                                                            // push  es
  *p++ = 0x89; *p++ = 0xE5;                                               // mov   bp, sp
  *p++ = 0x8E; *p++ = 0x5E; *p++ = 0x16;                                  // mov   ds, [bp + 0x16]
  *p++ = 0x89; *p++ = 0xEE;                                               // mov   si, bp
  *p++ = 0xFC;                                                            // cld
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->es; *p++ = (uint8)((uint16)&pRegs->es >> 8);  // mov [], ax (es)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->ds; *p++ = (uint8)((uint16)&pRegs->ds >> 8);  // mov [], ax (ds)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->edi; *p++ = (uint8)((uint16)&pRegs->edi >> 8);  // mov [], ax (di)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->esi; *p++ = (uint8)((uint16)&pRegs->esi >> 8);  // mov [], ax (si)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->ebp; *p++ = (uint8)((uint16)&pRegs->ebp >> 8);  // mov [], ax (bp)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->ebx; *p++ = (uint8)((uint16)&pRegs->ebx >> 8);  // mov [], ax (bx)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->edx; *p++ = (uint8)((uint16)&pRegs->edx >> 8);  // mov [], ax (dx)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->ecx; *p++ = (uint8)((uint16)&pRegs->ecx >> 8);  // mov [], ax (cx)
  *p++ = 0xAD;                                                            // lodsw          
  *p++ = 0xA3; *p++ = (uint8)&pRegs->eax; *p++ = (uint8)((uint16)&pRegs->eax >> 8);  // mov [], ax (ax)
  *p++ = 0x83; *p++ = 0xC4; *p++ = 0x14;                                  // add   sp, 0x14
  *p++ = 0x07;                                                            // pop   es
  *p++ = 0x1F;                                                            // pop   ds
  *p++ = 0x61;                                                            // popa
  *p++ = 0xCB;                                                            // retf
  f();
  return (uint16)pRegs->eax;
#endif
}
struct
{
  uint16 Ip, Cs;
} XmsEntryPoint = { 0 };
int XmsSupported(void)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x4300;
  RmInt(0x2F, &regs);
  return (regs.eax & 0xFF) == 0x80;
}
void XmsInit(void)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x4310;
  RmInt(0x2F, &regs);
  XmsEntryPoint.Cs = regs.es;
  XmsEntryPoint.Ip = (uint16)regs.ebx;
}
int XmsQueryVersions(uint16* pXmsVer, uint16* pHimemVer)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x00 << 8;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  if (pXmsVer != NULL)
    *pXmsVer = (uint16)regs.eax;
  if (pHimemVer != NULL)
    *pHimemVer = (uint16)regs.ebx;
  return (int)(regs.ebx & 0xFF);
}
int XmsQueryFreeMem(uint16* pLargest, uint16* pTotal)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x08 << 8;
  regs.ebx = 0;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  if (pLargest != NULL)
    *pLargest = (uint16)regs.eax;
  if (pTotal != NULL)
    *pTotal = (uint16)regs.edx;
  return (int)(regs.ebx & 0xFF);
}
int XmsAllocMem(uint16* pHandle, uint16 Size)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x09 << 8;
  regs.edx = Size;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  *pHandle = (uint16)regs.edx;
  return (int)(regs.ebx & 0xFF);
}
int XmsFreeMem(uint16 Handle)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x0A << 8;
  regs.edx = Handle;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  return (int)(regs.ebx & 0xFF);
}
int XmsLockMem(uint16 Handle, uint32* pPhysAddr)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x0C << 8;
  regs.edx = Handle;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  *pPhysAddr = ((regs.edx & 0xFFFF) << 16) | (regs.ebx & 0xFFFF);
  return (int)(regs.ebx & 0xFF);
}
#if defined(__TURBOC__)
int XmsCopyMem(uint16 DstHandle, uint32 DstOffs, uint16 SrcHandle, uint32 SrcOffs, uint32 Size)
{
  tDpmiRmInt regs;
#pragma pack(push, 1)
  struct
  {
    uint32 Size;
    uint16 SrcHandle;
    uint32 SrcOffs;
    uint16 DstHandle;
    uint32 DstOffs;
  } emm;
#pragma pack(pop)
  emm.Size      = Size;
  emm.SrcHandle = SrcHandle;
  emm.SrcOffs   = SrcOffs;
  emm.DstHandle = DstHandle;
  emm.DstOffs   = DstOffs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x0B << 8;
  regs.ds = FP_SEG(&emm);
  regs.esi = FP_OFF(&emm);
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  return (int)(regs.ebx & 0xFF);
}
#endif
int XmsUnlockMem(uint16 Handle)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x0D << 8;
  regs.edx = Handle;
  regs.cs = XmsEntryPoint.Cs;
  regs.ip = XmsEntryPoint.Ip;
  RmFarCall(&regs);
  return (int)(regs.ebx & 0xFF);
}
#if defined(__WATCOMC__)
int DpmiMap(void** pPtr, uint32 PhysAddr, uint32 Size)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x800;
  regs.ebx = PhysAddr >> 16;
  regs.ecx = PhysAddr & 0xFFFF;
  regs.esi = Size >> 16;
  regs.edi = Size & 0xFFFF;
  RmInt(0x31, &regs);
  *pPtr = (void*)(((regs.ebx & 0xFFFF) << 16) | (regs.ecx & 0xFFFF));
  return regs.flags & 1;
}
int DpmiUnmap(void* Ptr)
{
  tDpmiRmInt regs;
  memset(&regs, 0, sizeof(regs));
  regs.eax = 0x801;
  regs.ebx = (uint32)Ptr >> 16;
  regs.ecx = (uint32)Ptr & 0xFFFF;
  RmInt(0x31, &regs);
  return regs.flags & 1;
}
#endif
int main(void)
{
  uint16 xmsVer, himemVer;
  uint16 largestFreeSz, totalFreeSz;
  uint16 handle;
  uint32 physAddr;
#if defined(__WATCOMC__)
  {
    uint32 cr0__ = 0, cr3__ = 0;
    __asm
    {
      mov eax, cr0
      mov cr0__, eax
      mov eax, cr3
      mov cr3__, eax
    }
    printf("CR0: 0x%08lX, CR3: 0x%08lXn", (ulong)cr0__, (ulong)cr3__);
  }
#endif
  if (!XmsSupported())
  {
    printf("XMS unsupportedn");
    goto Exit;
  }
  printf("XMS supportedn");
  XmsInit();
  printf("XMS entry point: 0x%04X:0x%04Xn",
         XmsEntryPoint.Cs, XmsEntryPoint.Ip);
  XmsQueryVersions(&xmsVer, &himemVer);
  printf("XMS version: 0x%X  Himem.sys version: 0x%Xn",
         xmsVer, himemVer);
  XmsQueryFreeMem(&largestFreeSz, &totalFreeSz);
  printf("Largest free block size: %u KB  Total free memory: %u KBn",
         largestFreeSz, totalFreeSz);
  printf("Allocating the DMA buffer...n");
  if (XmsAllocMem(&handle, 64))
  {
    printf("Failed to allocate the DMA buffern");
    goto Exit;
  }
  XmsQueryFreeMem(&largestFreeSz, &totalFreeSz);
  printf("Largest free block size: %u KB  Total free memory: %u KBn",
         largestFreeSz, totalFreeSz);
  printf("Locking the DMA buffer...n");
  if (XmsLockMem(handle, &physAddr))
  {
    printf("Failed to lock the DMA buffern");
  }
  else
  {
    printf("The DMA buffer is at physical address: 0x%08lXn", (ulong)physAddr);
#if defined(__WATCOMC__)
    {
      uint8* ptr;
      printf("Mapping the DMA buffer...n");
      if (DpmiMap((void**)&ptr, physAddr, 64 * 1024UL))
      {
        printf("Failed to map the DMA buffern");
      }
      else
      {
        printf("The DMA buffer is at virtual address: 0x%08lXn", (ulong)ptr);
        printf("Using the DMA buffer...n");
        strcpy(ptr, "This is a test string in the DMA buffer.");
        printf("%sn", ptr);
        DpmiUnmap(ptr);
      }
    }
#elif defined(__TURBOC__)
    {
      char testStr[] = "This is a test string copied to and from the DMA buffer.";
      printf("Using the DMA buffer...n");
      if (XmsCopyMem(handle, 0, 0, ((uint32)FP_SEG(testStr) << 16) + FP_OFF(testStr), sizeof(testStr)))
      {
        printf("Failed to copy to the DMA buffern");
      }
      else
      {
        memset(testStr, 0, sizeof(testStr));
        if (XmsCopyMem(0, ((uint32)FP_SEG(testStr) << 16) + FP_OFF(testStr), handle, 0, sizeof(testStr)))
        {
          printf("Failed to copy from the DMA buffern");
        }
        else
        {
          printf("%sn", testStr);
        }
      }
    }
#endif
    XmsUnlockMem(handle);
  }
  XmsFreeMem(handle);
  XmsQueryFreeMem(&largestFreeSz, &totalFreeSz);
  printf("Largest free block size: %u KB  Total free memory: %u KBn",
         largestFreeSz, totalFreeSz);
Exit:
  return 0;
}

样本输出（在DosBox下）：

CR0: 0x00000001, CR3: 0x00000000
XMS supported
XMS entry point: 0xC83F:0x0010
XMS version: 0x300  Himem.sys version: 0x301
Largest free block size: 11072 KB  Total free memory: 11072 KB
Allocating the DMA buffer...
Largest free block size: 11008 KB  Total free memory: 11008 KB
Locking the DMA buffer...
The DMA buffer is at physical address: 0x00530000
Mapping the DMA buffer...
The DMA buffer is at virtual address: 0x00530000
Using the DMA buffer...
This is a test string in the DMA buffer.
Largest free block size: 11072 KB  Total free memory: 11072 KB

注意DOS/32不支持页面翻译（除非有VCPI）。CR0的PG位是0，CR3是0，并且获得的物理地址和虚拟地址是相同的，一切都说明了这一点。因此，虚拟地址和物理地址是一样的。

我写了一个应用程序来测试DOS中的AHCI（我的环境是DOS 7.0+DOS32a+Watcom C），下面列出了我如何为DMA传输分配内存，供您参考。

（1）以平面模式分配内存（假设分配1K内存，并且应该是WORD对齐）

ptr = (pDWORD)calloc(1024+1, sizeof(BYTE));

其中1024是我们真正需要的，1Byte表示"容差"，因为返回的指针可能不是字对齐的，最坏的情况是Exptr指向0x3000001

（2）基于WORD（2字节）调整对齐

if(inputAddr & 1) { inputAddr &= (~2 + 1); inputAddr += 2; }

（3）将上面的inputAddr分配给PRDT的DBA（数据库地址）

注意：

1） 我通过makefile中的"…wpp386-mf…"和链接器文件中的"op stub=dos23a.exe"使用了"平面内存模式"。。。

2） 其中ptr是指向已分配内存部分的实际指针，在释放内存时应保留该指针inputAddr是另一个指针，指向用于数据传输的正确（对齐）内存地址！

通过这种方式，DMA传输测试是可以的，在这种环境下分配的内存可以高达4MB。。。

F.Y.I

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