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comp.os.ms-windows.programmer.vxd Frequently Asked Questions (FAQ)


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Archive-name: windows/programming/vxd
Posting-Frequency: bimonthly
Last-modified: Aug 6, 1997

See reader questions & answers on this topic! - Help others by sharing your knowledge
                        Frequently Asked Questions (FAQ)
                                       for
                        comp.os.ms-windows.programmer.vxd

Editor:   Stephen Lewin-Berlin (berlin@vireo.com).
This document is copyright =A9 1995-1997 by Stephen Lewin-Berlin.

This document, like most FAQ documents, is a work in progress.  If you have
comments, additional questions, or additional answers, please forward them=
 to
the editor. If you write a good Questions and Answer, it will almost=
 certainly
be included.

The FAQ is distributed to the newsgroup every few weeks, but the text is
typically updated every few months. If you are reading this off-line, I
encourage you to check for an updated copy. The most recent copy can be=
 found on
many newsgroup archive sites, and at=
 ftp://ftp.vireo.com/biz/vireo/.

There is no permanent archive of the newsgroup.  Recent articles may be=
 located
at http://www.dejanews.com.

Contributors:  Raymond Chen, Lee Fisher, Michael Geary,
       Chris Marriott, Raymond Chen, Dan Norton,
       Don Matthews, Karen Hazzah, Stephen Lewin-Berlin, and others.

Questions
 Help, I need a driver for ...
 What are the differences between device drivers for Windows 3.1, Windows=
 3.11,
 Windows 95, and Windows NT?
 What is Windows Driver Model (WDM)?
 What is a VxD?
 Can I use Windows as a real-time operating system?
 How do I access physical memory at (e.g. D000:0000) from a Windows 3.1
 application?
 What are the differences between embedded, installable, and conventional
 device drivers?
 I need to write a Windows device driver.  Should it be a DLL or a VxD?
 How do I call an application from a VxD?
 How do I handle interrupts in my VxD?
 How do I access physical memory in my VxD?
 How do I access memory from my application or DLL in my VxD?
 How do I allocate memory from a Win16 application that can be accessed by a
 VxD at interrupt time?
 How do I share memory between a Win32 application and a VxD?
 Give me an overview of Plug and Play
 How do I initiate DMA from a VxD?
 Do I need a Device ID for my VxD?
 Can I write device drivers in C/C++, or must I use assembly language?
 Why do I get linker warnings when I build my VxD?
 Why can=92t I use MSVC 4.1 to build a VxD?
 What commercial products are available to help develop VxDs?
 How do I find someone to write a driver for me?
 What books and magazines are available?
 What on-line resources are available?
 Are there classes in device driver development available?
 Statement of interest
=20
Answers


Help, I need a driver for ...
     I'm afraid you've asked on the wrong group. This is a newsgroup for
     discussions of device driver programming, not for requesting drivers=
 for
     particular devices. I'm sure you'll get help if you ask on the correct
     newsgroup, which is "comp.os.ms-windows.setup".

What are the differences between device drivers for Windows 3.1, Windows=
 3.11,
Windows 95, and Windows NT?
     Windows 3.x and Windows 95 share a common device driver model.  Windows=
 NT
     depends an a completely new, and completely incompatible driver model.
     Let's discuss Windows 3.x and Windows 95 first, then a brief word about
     Windows NT, and finally some discussion about compatibility between NT=
 and
     Windows 3.x/95.
    =20
     There are really two kinds of device drivers for Windows 3.x/95. =
 Virtual
     Device Drivers (VxDs) run as part of the privileged (ring-0) operating
     system. VxDs can be thought of as a DLL for the operating system. =
 Running
     at ring 0, VxDs have complete access to the physical hardware, and can
     access data in the address space of any DOS, Windows, or Protected Mode
     application.  Under Windows 3.x, VxDs are typically given a .386 file
     extension, and are loaded when Windows starts.  Under Windows 95, VxDs=
 are
     given the .VXD file extension, and may be loaded at startup time, or
     dynamically loaded later.
    =20
     Windows 95 uses the same basic architecture for VxDs as Windows 3.x. =
 Thus,
     drivers written for Windows 3.x can be loaded on a Windows 95 system=
 and
     should generally work fine.  However, Windows 95 adds hundreds of new
     services for VxDs, and extends the VxD architecture to allow full=
 dynamic
     loading, pageable code and data, access to the system registry,=
 interfaces
     to Win32 applications, and many other features.  VxDs written for=
 Windows
     95 cannot be loaded on a Windows 3.x system.
    =20
     In addition to VxDs, Windows 3.x/95 supports non-privileged (ring-3)
     Communication and Printer drivers.  These are typically given .DRV file
     extensions.
    =20
     Windows NT uses a new driver architecture, called "Kernel Mode=
 Drivers".
     Refer to the Windows NT DDK for detailed information.  VxDs are not
     compatible with Windows NT.
    =20
     In order to provide compatibility between Windows NT and Windows=
 95/3.x,
     Microsoft provides "Miniport Drivers" for certain kinds of devices.
     Miniports allow driver developers to write a single driver using a pre-
     defined interface that is provided on both Windows NT and Windows=
 95/3.x.
     Microsoft provides Miniport drivers for SCSI, Printer, and Display=
 devices.

What is Windows Driver Model (WDM)?
     WDM, or Win32 Driver Model, was announced with much fanfare at the=
 Windows
     Hardware Engineering Conference (WinHEC) in March, 1996. WDM is a=
 standard
     API for device driver development under Windows that will be supported
     across Windows 98 and Windows NT platforms. WDM will be based on the
     Windows NT driver model, with additions to support Plug and Play.=
 Although
     the definition has not been released, Microsoft has said that a future
     release of Windows 95 will support a subset of the Windows NT device=
 driver
     services and architecture.
    =20
     Microsoft will initially support new buses (such as USB and P1394) with=
 WDM
     =93class drivers=94. Support for sound and input devices is also=
 planned
     =93sooner rather than later.=94 No specific commitment has been made=
 regarding
     other classes of devices.
    =20
     It appears that VxDs will continue to be required for many classes of
     drivers (for example, file system drivers for Windows 98) for the
     indefinite future.

What is a VxD?
     "VxD" stands for Virtual "something" Device, where 'x' stands for
     "something". Microsoft often names drivers according to this=
 convention,
     thus "VKD" is the Virtual Keyboard Device, and "VPICD" is the Virtual
     Programmable Interrupt Device.  VxDs are loaded into the protected=
 (ring-0)
     operating system address space, and have full access to the system
     hardware.  VxDs can modify page tables directly, install true hardware
     interrupt handlers, and generally wreak unrestricted havoc on the=
 system.
     Of course, just because you *can* doesn=92t suggest that you *should*.
    =20
     VxDs can be used to virtualize physical hardware by intercepting
     application requests to use the hardware and arbitrating between=
 requests
     from different applications. In the more extreme case, VxDs can provide=
 a
     "virtual" device that is not actually present at all, by emulating the
     behavior of a hardware device.  VxDs, by virtue of their privileged=
 access
     to the system, can also be used to implement software monitors,=
 debuggers,
     and to modify the behavior of other software on the system.
    =20
     VxDs under Windows 95 are also used to implement many other components=
 of
     the operating system, including the protected mode file system (IOS and
     IFS), the Virtual Communication Architecture (VCOMM), plug and play
     (Configuration Manager, etc.), and network transport and protocol=
 drivers
     (NDIS).

Can I use Windows as a real-time operating system?
     Can you say =93semi-real-time?=94 Microsoft Windows is not designed as=
 a real
     time operating system. In other words, there are no guarantees of real=
 time
     performance. Let me repeat that. There are NO GUARANTEES for real time
     latency under any version of Microsoft Windows. If your application
     requires absolutely guaranteed real-time response, otherwise a plane=
 will
     crash, a nuclear reactor will melt down, or a patient may die, then DO=
 NOT
     use Windows as a platform. On the other hand, if you can design you
     application (hardware/software) to accommodate some delays, you will=
 find
     that in most cases, Windows can provide excellent average latencies.
    =20
     For example, experiments run on a 486/66 system with no other programs
     running suggest that a VxD can handle over 10,000 interrupts per second
     without losing any of them. However, as soon as other software is=
 loaded,
     interrupts begin to be dropped.
    =20
     Windows is an =93open system=94 in the sense that applications and=
 drivers can
     disable interrupts at will. If one device driver disables interrupts=
 for a
     long period of time, no interrupt servicing will be performed. While=
 new
     drivers tend to keep interrupts disabled for very short periods, older
     drivers and applications sometimes poll hardware devices and keep
     interrupts disabled for unpredictable amounts of time.
    =20
     Of course, you can write a driver that disables interrupts and polls=
 YOUR
     hardware. The mouse and keyboard will not respond, and other device=
 driver
     developers will grumble and curse if your driver happens to running on=
 a
     system where THEY want to do real-time-like operations. However, this=
 may
     be an acceptable alternative for in-house projects, or on well=
 controlled
     systems.
    =20
     The only real answer is to test your driver with a wide variety of=
 software
     and hardware installed and gather empirical evidence. If you have the
     luxury to control the design of the hardware, build in buffering to
     accommodate worst-case latency situations.

How do I access physical memory at (e.g. D000:0000) from a Windows 3.1
application?
     This is very easy to do.  Here is a sample program that references the=
 VGA
     display buffer at A000:0000.  You can use the same technique, except=
 use
     _D000h instead of _A000h.  KERNEL defines a whole set of these=
 selectors
     for you covering the A000 through F000 range.
       #define STRICT
       #include "windows.h"
      =20
       typedef WORD SELECTOR;
      =20
       // __A000h is an absolute value; by declaring it as a NEAR variable
       // in our data segment we can take its "address" and get the
       // 16-bit absolute value.
      =20
       extern BYTE NEAR CDECL _A000h;     // use _A000H for Borland=
 compilers
      =20
       SELECTOR selVGA =3D (SELECTOR)&_A000h;
      =20
       int PASCAL WinMain (HINSTANCE   hinst,
                                HINSTANCE   hinstPrev,
                                LPSTR       lpszCmdLine,
                                int         cmdShow
                                )
       {
            WORD FAR * lpVGA =3D MAKELP( selVGA, 0 );
      =20
            // Should put garbage pixels on top left of screen
            lpVGA[0] =3D 0x1234;
            lpVGA[1] =3D 0x5678;
      =20
            return 0;
       }
      =20

What are the differences between embedded, installable, and conventional=
 device
drivers?
     All of these terms can be used to describe 16-bit protected-mode DLLs.
    =20
     >    An embedded device driver is a DLL that basically acts as an=
 extension
          of a particular Windows application.  It usually contains an=
 interrupt
          handler, and it exports any set of services the author might=
 choose to
          implement.
    =20
     >    An installable device driver must conform to more rigid=
 guidelines.
          This type of driver can be opened, closed, enabled, disabled, etc.=
 by
          other applications or DLLs.  It contains a DriverProc, which is=
 like
          the WindowProc in a Windows application.  The DriverProc responds=
 to a
          standard set of messages sent by Windows and to custom messages=
 sent
          by applications.  This is the type of driver that can be installed
          using the Control Panel applet.
    =20
     >    A conventional device driver (also sometimes called a "standard"
          device driver) interacts with a hardware device supported by the
          Windows API.  For example, the display, keyboard, and printer are
          considered to be "standard" devices.  These drivers are sometimes
          given a file extension of .DRV, and are usually installable=
 drivers.
          They work with certain pre-defined data structures and provide=
 certain
          pre-defined services.

I need to write a Windows device driver.  Should it be a DLL or a VxD?
     This is the kind of question whose answer really depends on your
     application and your objectives.  In general, a VxD is more difficult=
 to
     develop, but yields higher performance when processing interrupts and
     accessing I/O ports.  A VxD can also do things that aren't otherwise
     possible with a DLL.
    =20
     The first step is to determine what it is that your driver must do.  If=
 it
     must support a hardware device, then which of the following system
     resources are required by your hardware?
    =20
          a.)  I/O ports
          b.)  IRQ lines
          c.)  Memory ranges
          d.)  DMA channels
    =20
     If I/O ports are involved, then be aware that there are performance=
 issues
     related to accessing I/O ports from ring 3, as you would in a DLL, as
     compared to accessing them from ring 0 in a VxD.  There is overhead
     associated with accessing I/O ports from ring 3, perhaps as much as=
 100% or
     more (i.e. ring 3 accesses take twice as much time as ring 0 accesses).=
 If
     the port is trapped by another driver, then the overhead to access the=
 port
     will be drastically greater.
    =20
     If IRQ lines are involved, then be aware that there is significantly=
 more
     interrupt latency associated with an ISR running in ring 3 than in a=
 VxD.
    =20
     Access to physical memory can be accomplished with DPMI services in a=
 DLL,
     or VMM services in a VxD.
    =20
     Access to DMA channels from application level should go through VDS
     (Virtual DMA Services).
    =20
     If you need to make your hardware appear to be shared by Windows
     applications and DOS applications running in separate DOS boxes, then=
 you
     need to "virtualize" your hardware with a VxD.  You also need to
     "virtualize" your hardware if you need to mediate access, or resolve
     contention for your device.
    =20
     Note also that VxDs are not supported for Windows NT or OS/2, as those
     operating systems use a different form of device driver.  DLLs should=
 work
     correctly across the platforms.
    =20

How do I call an application from a VxD?
     There are several possibilities, depending on what kind of application=
 you
     are calling, and whether the driver is running under Windows 3.x or=
 Windows
     95.
    =20
     Here is a brief outline of some of the options.
    =20
     Windows 3.x
          Use Nested Execution services to call PostMessage to send a=
 message to
     a Windows application.
          Use Nested Execution services to simulate a call or interrupt into=
 a
     V86 or Protected Mode context.
     Windows 95
          Use Nested Execution services to call PostMessage to send a=
 message to
     a Windows application.
          Use Nested Execution services to simulate a call or interrupt into=
 a
     V86 or Protected Mode context.
          Use Shell_Post_Message to post a message to a Windows application.
          Use shell services such as Shell_Call_At_Appy_Time or
     Shell_Post_Message.
          Use Vwin32_QueueUserAPC to initiate a User Asynchronous Procedure
     Call.

How do I handle interrupts in my VxD?
    =20
     Use the services provided by the Virtual PIC Device (VPICD) to install=
 an
     ISR for your hardware device.  This involves creating a data structure=
 in
     the locked data segment of your VxD of type VPICD_IRQ_Descriptor.  In=
 it,
     you specify the IRQ number and the address of your ISR, among other=
 things.
     You then register your ISR by calling VPICD_Virtualize_IRQ.  This=
 returns
     an IRQ Handle, which you should save for future reference.
    =20
     Later, when an interrupt occurs, your ISR will be entered with minimal
     latency.  The ISR must be in a locked code segment.  The IRQ Handle=
 that
     uniquely identifies this interrupt will be in EAX upon entry.  You=
 should
     call VPICD_Phys_EOI at the end of your ISR.  Just before returning from
     your ISR, clear the carry flag if you successfully processed the=
 interrupt.
     If the IRQ is sharable, you can pass the IRQ on to the next handler in=
 the
     chain by setting the carry flag.  Return from the ISR with a RET
     instruction, not IRET.
    =20
     Upon entry to the VID_Hw_Int_Proc (your ISR), interrupts are masked at=
 the
     PIC for that particular interrupt, and an EOI has already been sent to=
 the
     PIC for that same interrupt.  The call to VPICD_Phys_EOI at the end of=
 the
     ISR doesn't actually send an EOI to the physical PIC, as the name=
 implies,
     but rather simply unmasks the interrupt at the PIC. The EOI was=
 actually
     sent to the PIC before entering VID_Hw_Int_Proc.  The name of the
     VPICD_Phys_EOI service is misleading.
    =20
     Check out the useful services provided by VPICD.

How do I access physical memory in my VxD?
    =20
     You should first convert the physical address to a linear address with=
 the
     _MapPhysToLinear service.  If you need to pass the address to an
     application, you can convert the linear address to either a=
 protected-mode
     address in (selector):(offset) form or a V86-mode address in
     (segment):(offset) form with the Map_Lin_To_VM_Addr service.

How do I access memory from my application or DLL in my VxD?
    =20
     You should convert the protected-mode address to a linear address with=
 the
     Map_Flat service.  Do not depend on the address remaining valid
     indefinitely unless you have locked the linear address with the=
 GlobalFix
     API.

How do I allocate memory from a Win16 application that can be accessed by a=
 VxD
at interrupt time?
     In order to allocate memory that is safe to access froma VxD at=
 interrupt
     time, you must perform several steps.
          GlobalAlloc()  Allocate a block of memory.
          GlobalLock()   Keep the segment in memory.
          GlobalFix()    Prevent the segment from moving in linear memory.
          GlobalPageLock()    Prevent the memory from being swapped to disk.
     Then, pass the segment:offset address of the memory block to the VxD.=
 The
     VxD can use the MapFlat service to translate the memory address to a=
 linear
     address for use by the ISR.
    =20

How do I share memory between a Win32 application and a VxD?
     Under Windows 95, VxDs and Win32 applications share the same linear=
 address
     space. Therefore, you can allocate memory in a VxD and pass the linear
     address to a Win32 application directly.  The address space of an
     application includes both private and shared regions. If a VxD needs to
     access memory allocated in a Win32 application, the memory must be in a
     shared (global) region, or the VxD must be running in thread context=
 from
     which the memory was originally allocated. Use the=
 Schedule_Thread_Event
     service to change contexts if necessary.
    =20
     If a VxD needs to access application memory at interrupt time, the=
 memory
     must be page locked. There are no Win32 services for page locking=
 memory,
     but the VxD may lock the pages. Use the VMM service  _LinPageLock,=
 setting
     the last parameter (flags) to PAGEMAPGLOBAL. The service returns an=
 address
     for the specified page that may is usable from any memory context. Use
     _LinPageUnLock to unlock the memory.

Give me an overview of Plug and Play
    =20
     If you write a VxD for a device in Win95, you must provide a Device
     Information  file (.INF) that tells Win95 how to install the VxD and =
 how
     to configure the device. Information about INF files can be found  in=
 the
     Win95 DDK.
    =20
     If you're writing a Win95 VxD for a PCI, PCMCIA or PNPISA device, you
     should also add Plug and Play support to your VxD. All that means is=
 that
     your VxD uses Configuration Manager (a VxD) services to find out which
     system resources (I/O addr, IRQ, etc.) have been assigned to the=
 device,
     as opposed to obtaining this info from an INI file or hardcoding it.
    =20
     To add this required Plug and Play functionality, your VxD must handle=
 the
     PNP_New_DevNode message sent by the Config Mgr. In response to this
     message,  you should register yourself as the device driver by calling
     CM_RegisterDeviceDriver. When calling this function, you pass the CM a
     callback function. The CM will call you back later when your resources=
 have
     been assigned, passing you a function code. When your callback =
 function is
     called with the CONFIG_START function code, call the function
     CM_GetAllocLogConf to find out which resources have been assigned to=
 your
     device. This call fills in a CM_CONFIG structure, which has a field for
     I/O address, IRQ, etc.
    =20
     Some types of VxDs, including SCSI MiniPort Drivers, Network Drivers=
 and
     VCOMM Port Drivers, may need to use a different method of obtaining=
 config
     info. These types are different because in each case another VxD is=
 acting
     as Device Loader, and it's the Device Loader that actually interacts=
 with
     the CM, not the driver VxD. These drivers may need to use configuration
     services  provided by the Device Loader (IOS, Ndis wrapper or VCOMM)
     instead  of interacting with the CM directly.
    =20
     The Configuration Manager will never send your VxD a PNP_New_DevNode
     message  until the appropriate registry entries are made. The best way=
 to
     get the  registry entries is not by hand, but with an INF file. Win95=
 will
     prompt  you for an INF file the first time it sees your device. For
     PCI,PCMCIA and  ISAPNP devices, this should automatically happen the=
 first
     time you  physically install the device. For other devices, you may=
 have to
     run the  Add New Hardware wizard from the Device Manager application.=
 Win95
     will  use the INF file you supply to make registry entries. INF files=
 are
     documented in the Win95 DDK.

How do I initiate DMA from a VxD?
    =20
     The following information applies to both Windows 3.x and Windows 95,
     unless  otherwise noted. It assumes some knowledge of DMA operations=
 under
     DOS,  describing only differences under Windows.
    =20
     A Windows driver for a DMA device can be implemented as a Ring 3 driver=
 DLL
     or as a VxD. A VxD will offer much better performance, because Ring 3=
 DMA
     generally results in double buffering.
    =20
     To set up a DMA transfer in a DLL, program the the system DMA=
 controller
     registers using normal I/O instructions, setting up the DMA mode,=
 count,
     address, etc. Use GlobalDosAlloc to allocate the DMA buffer. All other
     methods result in a linear address above 2 GB, larger than the 24-bit
     controller can address. GlobalDosAlloc returns a segment value and a
     selector value. Uses the segment value as you would under DOS to=
 calculate
     a physical address -- shift left by 4. Program this value into the
     controller's base address register, just like under DOS.
    =20
     So it's easy to do DMA from a DLL. But there's a cost to performance.=
 The
     VDMAD intercepts all I/O reads and writes to the DMA controller,=
 writing
     the  data to its own virtual registers but not to the actual registers.
     When the  DLL unmasks the controller, the VDMAD gets ready to start the=
 DMA
     operation.  VDMAD looks at the value written to the base address=
 register.
     Treating this  as a linear address, it determines if the pages are
     physically contiguous.  Only random chance would make them contiguous,
     because a Windows app or  DLL cannot specify contiguous when=
 allocating. If
     they're not (and they  won't be), the VDMAD writes into the actual
     controller register the physical  address of another buffer instead --=
 one
     allocated as contigous by VDMAD.  If transfer is from memory, VDMAD=
 copies
     data from original buffer to its  buffer. VDMAD programs the controller
     with the remaining virtual register  values, and the transfer begins.=
 If
     the transfer is to memory, VDMAD copies  from its buffer to the=
 original
     buffer when the transfer is complete. All  this is transparent to DOS=
 or
     Windows application that performed the transfer.  But the buffer copy
     required to insure DMA buffer physical contiguity may  slow down the
     transfer considerably.
    =20
     To do DMA in a VxD, allocate the DMA buffer with PageAllocate, using=
 the
     PageUseAlign and PageContig flag bits, and pType of PG_VM. Under=
 Win3.x,
     these flags are valid only during initialization. Under Win95, the=
 flags
     are  valid at any time. Do not program the system DMA controller=
 directly,
     use  VDMAD services. Call VDMAD_Virtualize_Channel once before the=
 first
     transfer  to reserve the channel. For every transfer, call
     VDMAD_Lock_DMA_Region  to page-lock the buffer and get it's physical
     address; VDMAD_Set_Region_Info  to program the controller with physical
     address; VDMAD_Set_Phys_State to  program the controller's mode; and=
 last
     VDMAD_Phys_Unmask_Channel to unmask  the channel. The VDMAD Lock and=
 Unlock
     services cannot be called in a ISR,  schedule an event handler instead=
 if
     necessary.

Do I need a Device ID for my VxD?
    =20
     Most developers will not need a device ID. To communicate with a VxD=
 from a
     Win32 application, use the Device IOCTL call. To obtain the VxD entry=
 point
     from a 16-bit application running under Windows 95 given the device=
 name (1-
     8 characters) without needing an ID number, do this:
    =20
           AX =3D 1684h (Get VxD entry point)
           BX =3D 0000h (UNDEFINED_DEVICE_ID)
           ES:DI -> 8-character space-padded case-sensitive buffer with the=
 VxD
     name.
           Int 2Fh
    =20
     This will return ES:DI =3D callback address if successful, or 0 on=
 error.
     For example, if your device is called "MYDEV", you could write
    =20
     MyDevName db 'MYDEV   ' ; 8 characters space-padded case-sensitive
          mov ax, 1684h
          mov bx, 0
          push ds
          pop es
          mov di, offset MyDevName
          int 2fh
          mov ax, es
          or ax, di
          jz error
          mov word ptr EntryPoint[0], di
          mov word ptr EntryPoint[2], es
    =20
     If your driver provides services to be called by other VxDs, you may=
 want a
     unique device ID. Send email to vxdid@microsoft.com and an application=
 for
     a device ID will be automatically sent to you.

Can I write device drivers in C/C++, or must I use assembly language?
    =20
     VxDs are 32-bit programs.  You may use a 32-bit C/C++ compiler, but you
     must be careful about segmentation, calling conventions, and run time
     library routines that require initialization.  Many of the interfaces
     provided by the Virtual Machine Manager have register-based calling
     conventions.
    =20
     Vireo Software sells a toolkit that allows you to use C or C++ to write
     VxDs.  See below.

Why do I get linker warnings when I build my VxD?
     The Microsoft linker will generate many warnings when linking VxDs. =
 The
     warning messages refer to =93mismatched segment attributes=94.  These=
 errors
     are normal (sorry about that) and can be ignored.  The most recent=
 linker
     includes a /IGNORE switch that you can use to at least suppress the
     messages.

Why can=92t I use MSVC 4.1 to build a VxD?
     There is a bug in Microsoft Visual C/C++ version 4.1 that prevents two=
 key
     macros (VxDjmp and VxDCall) from working correctly. The problem does=
 not
     appear in MSVC 4.0 or 4.2. A fix is available from Vireo Software.

What commercial products are available to help develop VxDs?
    =20
          Microsoft Developer Network   (Microsoft)
          Soft-ICE            (Nu-Mega Technologies)
          VtoolsD             (Vireo Software)
          VxBuild              (Tetradyne)
    =20
          Microsoft Developer Network
          Summary:    The Microsoft Developer Network is available in=
 several
                 versions. The basic version consists of a CD containing
                 product documentation and publications. Options include
                 subscriptions for quarterly updates, and SDK/DDK packages.=
 In
                 order to receive the DDK, you must (1) subscribe to the
                 "professional" edition or higher, and (2) request the DDK
                 specifically.  Although there is no additional charge for=
 the
                 DDK, it is only shipped to customers who specifically=
 request it.

          Contact:    Microsoft Developer Network
                 PO Box 10296, Des Moines, IA  50336
                 (800) 759-5474 or (206) 936-8661
    =20
          SoftICE/W
          Summary:    Soft-ICE/W is a full-screen character-mode debugger=
 that
                 can be used to debug VxDs and applications. Soft-ICE/W can
                 debug VxDs at the instruction level, or display ASM, C, or=
 C++
                 source code.
          Contact:    NuMega Technologies, Inc.
                 PO Box 7780, Nashua, NH  03060
                 (603) 889-2386
                 fax: (603) 889-1135
                 mailto:info@numega.com
                 http://www.numega.com
         =20
          VtoolsD for Windows 95
          Summary:    VtoolsD for Windows 95 allows developers to build VxDs
                 for Windows 95, including registry, plug and play, file=
 system
                 drivers, Win32 application interfaces, and much more.=
 VtoolsD
                 for Windows 95 includes Microsoft=92s WDEB386 debugger and=
 the
                 Windows 95 debug kernel along with over 40 sample VxDs.
          Contact:    Vireo Software
                 21 Half Moon Hill, Acton, MA  01720
                 (508) 264-9200
                 fax: (508) 264-9205
                 mailto:info@vireo.com
                 http://www.vireo.com
    =20
          VtoolsD for Windows 3.1
          Summary:    VtoolsD is a toolkit that allows developers to build=
 VxDs
                 in C or C++ using the Microsoft 32-bit C/C++ compiler.=
 VtoolsD
                 includes a visual-programming VxD code generator, ANSI C=
 run-
                 time libraries, VMM/VxD service libraries, examples, and a=
 VxD
                 Class Library.  Compatible with Microsoft and Borland C/C++
                 compilers.
          Contact:    Vireo Software
                 21 Half Moon Hill, Acton, MA  01720
                 (508) 264-9200
                 fax: (508) 264-9205
                 mailto:info@vireo.com
                 http://www.vireo.com
         =20
          VxBuild
          Summary:    Wrappers to build VxDs in C.
          Contact:    Tetradyne Software Inc.
                 2542 S. Bascom Ave, Suite #206
                 Campbell, CA 95008
                 (408) 377-6367
                 fax: (408) 377-6258
                 sales@tetradyne.com
                 http://www.tetradyne.com

How do I find someone to write a driver for me?
     Vireo Software maintains a list of consultants and contract programmers=
 who
     specialize in device driver software. Follow links from Vireo=92s home=
 page
     at http://www.vireo.com/consult.htm

What books and magazines are available?
     Magazines
          There are no magazines devoted strictly to device driver=
 programming.
          The following publications have published articles about device=
 driver
          technology at one time or another. Someday, I may have time to=
 collect
          references to specific articles.
         =20
          Microsoft Systems Journal
          Dr. Dobb=92s Journal
          Windows Developer=92s Journal
          Windows Tech Journal
    =20
    =20
     Books specifically about device drivers:
    =20
          Title:     Inside the Windows 95 File System
          Author:    Stan Mitchell
          Publisher: O'Reilly & Associates
          ISBN:      1-56592-200-X
          Price:     $32.95
    =20
          Title:    Systems Programming for Windows 95
          Author:   Walter Oney
          Publisher:     Microsoft Press
          ISBN:     1-55615-949-8
          Price:    $39.95
    =20
          Title:    Writing Windows VxDs and Device Drivers (2nd  edition)
          Author:   Karen Hazzah
          Publisher:     R&D Publications
          ISBN:     0-87930-438-3
          Price:    $49.95
         =20
          Title:    Writing Windows Virtual Device Drivers
          Author:   David Thielen and Bryan Woodruff
          Publisher:     Addison Wesley
          ISBN:     0-201-62706-X (may be replaced by:)
          ISBN:     0-201-48921-X
          Price:    $39.95
    =20
          Title:    Writing Windows Device Drivers
          Author:   Daniel Norton
          Publisher:     Addison Wesley
          ISBN:     0-201-57795-X
          Price:    $29.95
    =20
     Other books useful to device driver developers:
    =20
          Title:    Undocumented DOS (2nd Edition)
          Author:   Andrew Schulman et al
          Publisher:     Addison-Wesley
          ISBN:     0-201-63287-X
          Price:    $44.95
    =20
          Title:    DOS Internals
          Author:   Geoff Chappell
          Publisher:     Addison-Wesley
          ISBN:     0-201-60835-9
          Price:    $39.95
    =20
          Title:    Unauthorized Windows 95 Resource Kit
          Author:   Andrew Schulman
          Publisher:     IDG Books
          ISBN:     1-56884-305-4 (with disk)
          ISBN:     1-56884-169-8 (no disk)
          Price:    $39.95
    =20
    =20

What on-line resources are available?
    =20
     Internet news groups
          news:comp.os.ms-windows.programmer.vxd
          news:microsoft.public.win32.programmers.kernel
    =20
     World Wide Web sites
          http://www.vireo.com
               Vireo Software (VtoolsD) home page
          http://www.albany.net/~danorton/ddk
               Dan Norton=92s DDK resource page
          http://www.microsoft.com
               Microsoft home page
          http://www.ora.com/windows
               O=92Reilly Associates home page
          http://www.numega.com
               Nu-Mega Technologies (Soft-ICE) home page
          http://www.microsoft.com/windows/thirdparty/hardware
               Windows Hardware Technical Information for IHVs and OEMs
          http://www.teleport.com/~usb
               Universal Serial Bus Home Page
          http://www.tiac.net/users/waltoney
               DDK annotations
              =20
     Mailing lists
          DDK-L ($15.00 fee)
            This list is for discussion of Microsoft Windows Driver
            Development, including VxDs, printer drivers, and Windows NT=
 kernel
            mode drivers. To join, send "subscribe DDK-L first_name=
 last_name"
            in the body of a message to LISTSERV@PEACH.EASE.LSOFT.COM.  The
            list is free for the first 30 days.  After that, the fee is $15
            annually.  The up-to-the-minute archives are publicly available
            without charge at:
                http://www.albany.net/~danorton/ddk/ddk-l/index.shtml
          VCOMM  (Free)
            This is for discussion of VCOMM port driver development. To=
 join,
            send a  message to vcomm@cdsnet.net
             with the text "subscribe vcomm" in the body of the message. A
       VCOMM FAQ is also available.
          DDK (free)
            This list is for discussion of Microsoft Windows Driver
            Development, including VxDs, printer drivers, and Windows NT=
 kernel
            mode drivers. To join, send "SUBSCRIBE DDK" in the body of a
            message to Majordomo@cfn.ist.utl.pt
    =20
     Internet FTP sites
          ftp://ftp.microsoft.com/Developr/drg/developer-info/
               This file contains a list of developer resources available=
 from
          Microsoft; it is not driver specific.
          ftp://ftp.microsoft.com/Developr/MSDN
          ftp://ftp.microsoft.com/Developr/DRG/MSDN-Info
               These directories contain additional information about=
 Microsoft
          Developer Network.
          ftp://ftp.ora.com/pub/examples/windows/win95.update/
         =
 ftp://ftp.microsoft.com\developr\drg\winsock\ms-extensions\vxdtdi.zip
               Documents how to access the TCP/IP stack

Are there classes in device driver development available?
    =20
     Walter Oney  Software
          Walter Oney offers training classes in VxD development.
          Walter Oney Software
          4 Longfellow Place
          Boston, MA  02114
          800.737.9876
          fax: 617 227 5760
          WaltOney@oneysoft.com
    =20

Statement of interest
    =20
     The editor works for Vireo Software, Inc. and is one of the authors of=
 the
     VtoolsD VxD toolkit mentioned in this document.
    =20
     -- Steve Lewin-Berlin
          Berlin@vireo.com
          Vireo Software
          "The Device Driver Tools Company"


  Stephen Lewin-Berlin                  mailto:berlin@vireo.com
  Vireo Software                        http://www.vireo.com
  "The Device Driver Tools Company"

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Last Update March 27 2014 @ 02:12 PM