> For the complete documentation index, see [llms.txt](https://docs.hex-rays.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hex-rays.com/8.4/developer-guide/idc/idc-examples/device-driver-analysis.md).

# Device driver analysis

This program is automatically executed when a new device driver is loaded.

```
//
//      This file is executed when a new device driver is loaded.
//              Device drivers have extensions DRV or SYS.
//

#include <idc.idc>

static main(void) {
  auto x,i,base;
  auto intr,strt;
  auto attr,cmt;
  auto nextbase;
  auto DevReq;

  i = 0;
  x = MinEA();
  base = (x >> 4);   // The segment base

  while ( 1 ) {
    Message("Device driver block at %04X\n",x);

    MakeName(x,form("NextDevice_%ld",i));
    MakeWord(x);
    OpNumber(x,0);
    if ( Word(x) == 0xFFFF ) {
      MakeComm(x,"The last device");
    } else {
      nextbase = base + Word(x+2);
      OpOff(x,0,[nextbase,0]);
      MakeComm(x,"Offset to the next device");
    }

    MakeWord(x+2);
    OpNumber(x+2,0);

    MakeName(x+4,form("DevAttr_%ld",i));
    MakeWord(x+4);
    OpNumber(x+4,0);
    attr = Word(x+4);
    cmt = "";
    if ( attr & (132M\n");
    if ( attr & (1 Device Request Block");
    MakeComm( intr, "Device Request Block:\n"
          "0 db length\n"
      "1 db unit number\n"
      "2 db command code\n"
      "5 d? reserved\n"
      "0D d? command specific data");

    if( Byte( strt )==0x2E && Word(strt+1)==0x1E89
     && Byte(strt+5)==0x2E && Word(strt+6)==0x068C
     && Word(strt+3)==Word(strt+8)-2)
    {
     DevReq=Word(strt+3);
     Message("DevReq at %x\n",DevReq);
     MakeUnkn(x+DevReq,0);MakeUnkn(x+DevReq+2,0);
     MakeDword(x+DevReq);MakeName(x+DevReq,form("DevRequest_%ld",i));
    }

    if ( Word(x) == 0xFFFF ||
       ((Byte(x)==0xE9 || Byte(x)==0xEB) && i==0) ) break;
    if ( Dword(x) == 0 ) break;	// 04.01.96
    x = [ nextbase, Word(x) ];
    i = i + 1;
  }
}
          
```


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