Amiga Plus 1995 #2/Amiga Plus CD - 1995 - No. 2.iso/internet/faq/englisch/comp.os.ms-windows.programmer

Text File | 1995-04-11 | 15.8 KB | 408 lines

Archive-name: windows/programming/device-drivers
Posting-Frequency: bimonthly
Last-modified: February 9, 1995


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

Summary:
    This is a working document.  Suggestions, questions, answers,
    are welcome.  I will post this document near the beginning of
    each month.  This FAQ is particularly thin on Windows NT driver
    information (that's a hint for you NT driver wizards out there
    to send in some info...).

    Thanks for help, comments, and answers from Lee Fisher, Michael Geary,
    Chris Marriott, Dan Norton, and especially Don Matthews.

    Edited by Steve Lewin-Berlin ([e-mail])

Questions:

 1.  Help, I need a driver for...
 2.  How do I access physical memory at <addr> from a Windows 3.1 application?
 3.  What are the differences between embedded, installable, and conventional
     device drivers?
 4.  I need to write a Windows device driver.  Should it be a DLL or a VxD?
 5.  How do I handle interrupts in my VxD?
 6.  How do I access physical memory in my VxD?
 7.  How do I access memory from my application or DLL in my VxD?
 8.  Can I write device drivers in C/C++, or must I use assembly language?
 9.  What commercial products are available to help write drivers?
10.  What books are available?
11.  What on-line resources are available?
12.  What other information is available?

Answers:

 1.  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".

 2.  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.

         #include "nojunk.h"
     #define STRICT
     #include <windows.h>

     typedef WORD SELECTOR;

     // __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.

     extern BYTE NEAR CDECL _A000h;

     SELECTOR selVGA = (SELECTOR)&_A000h;

     int PASCAL WinMain (HINSTANCE   hinst,
                 HINSTANCE   hinstPrev,
                 LPSTR       lpszCmdLine,
                 int         cmdShow
                 )
    {
    WORD FAR * lpVGA = MAKELP( selVGA, 0 );

    // Should put garbage pixels on top left of screen
    lpVGA[0] = 0x1234;
    lpVGA[1] = 0x5678;

    return 0;
    }


 3.  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.

   o 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.

   o 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.

   o 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.

 4.  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.

     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?

     a.)  I/O ports
     b.)  IRQ lines
     c.)  Memory ranges
     d.)  DMA channels

     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 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 DLL.

     Access to physical memory can be accomplished with DPMI services in
     a DLL, or VMM services in a VxD.

     Access to DMA channels should go through VDS (Virtual DMA Services).

     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.

 5.  How do I handle interrupts in my VxD?

     You should 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.

     Later, when an interrupt occurs, your ISR will be entered with minimal
     latency.  The ISR should 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.

     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.

     Check out the useful services provided by VPICD.

 6.  How do I access physical memory in my VxD?

     You should first convert the physical address to a linear address
     with the _MapPhysToLinear service.  Then 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.

 7.  How do I access memory from my application or DLL in my VxD?

     You should convert the protected-mode address to a linear address
     with the Map_Flat service.

 8.  Can I write device drivers in C/C++, or must I use assembly language?

     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.

     Vireo Software sells a toolkit that allows you to use C or C++ to
     write VxDs.  See below.

 9.  What commercial products are available to help write device drivers?

        MSDN level 1   (Microsoft)
        MSDN level 2   (Microsoft)
        Soft-ICE/W     (Nu-Mega Technologies)
        VtoolsD        (Vireo Software)

    MSDN level 1
        Summary:  Membership in level 1 of the Microsoft Developer Network
              gets you a CD 4 times per year. The CD is packed with
              documentation and on-line books, including articles about
              VxD development.
        Price:    $195/ year
        Contact:  Microsoft Developer Network
              mail:  PO Box 10296, Des Moines, IA  50336
              voice: [phone]
              voice: [phone]
              CIS:  go MSDS

    MSDN level 2
        Summary:  Membership in level 2 of the Microsoft Developer Network
              gets you a set of CDs 4 times per year.  The CDs include
              the level-1 CD (see above) plus operating systems, SDKs,
              and DDKs for a number of MS products.  This includes the
              Windows Device Driver Kit (DDK), which includes
              utilities required to build device drivers, along with
              numerous examples.
        Price:    $495/ year
        Contact:  MSDN (see above)

    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,
              and a VxD Class Library.  Compatible with Microsoft and
              Borland C/C++ compilers.
        Price:    $495
        Contact:  Vireo Software
              mail:  385 Long Hill Road, Bolton, MA  01740
              voice: [phone]
              fax:   [phone]
              Email: [e-mail]

    VtoolsD for Windows 95 (Pre-release)
        Summary:  The Windows 95 Pre-release allows developers to build
              VxDs that call new services available in Windows 95.
              Requires Windows 95 DDK.
        Price:    $495
        Contact:  Vireo Software (see above)

    Soft-ICE/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.
        Price:    $386
        Contact:  Nu-Mega Technologies, Inc.
              mail:  PO Box 7780, Nashua, NH  03060
              voice: [phone]
              fax:   [phone]

10.  What books are available?

        Writing Windows Device Drivers           (Daniel Norton)
        Writing Windows Virtual Device Drivers   (Thielen and Woodruff)

        Title:    Writing Windows Virtual Device Drivers
        Author:    David Thielen and Bryan Woodruff
        Publisher:    Addison Wesley
        ISBN:    0-201-62706-X
        Price:    $39.95

        Title:    Writing Windows Device Drivers
        Author:    Daniel Norton
        Publisher:    Addison Wesley
        ISBN:    0-201-57795-X
        Price:    $29.95

11.  What on-line resources are available?

        CompuServe
        Internet

        Internet news groups
        comp.os.ms-windows.programmer.drivers

        Internet FTP site
        ftp.microsoft.com
            Developr/drg/developer-info/devinfo.zip
                This file contains a list of developer resources
            available from Microsoft; it is not driver specific.
            Developr/MSDN/
            Developr/DRG/MSDN-Info/
                These directories contain additional information
            about Microsoft Developer Network.

        CompuServe
            Microsoft operates several forums on CompuServe that may
        be of interest to device driver developers:

        Microsoft Developer Knowledge Base      Service: MDKB

            The Microsoft Developer Knowledge Base is a reference tool
            containing technical information and articles about the
            Microsoft developer-specific products.  This database is
            compiled and maintained by Microsoft Product Support and is
            full-text, keyword searchable. You will find Microsoft
            press releases and technical articles about product bugs,
            trouble-shooting and updates.

        Microsoft Developer Network Forum       Service: MSDNLIB

            The Microsoft Developer Network (MSDN) Technical Library
            Forum offers software developers a quick and efficient way
            of obtaining technical information.  The libraries contain
            a collection of technical articles in the Windows Help file
            format and sample code, which are available for
            downloading. Message sections enable you to discuss any of
            the files or codes with other users, as well as with
            Microsoft Representatives.

        Microsoft Knowledge Base        Service: MSKB

            Microsoft Knowledge Base is a database which provides
            access to information about Microsoft products previously
            available only to the Microsoft support engineers. Search
            the database by product name, version or category. Or for
            immediate responses to your questions, perform a full-text
            search of all documents contained within database that
            contain the subject of your question. Also communicate
            directly with Microsoft by sending an electronic message to
            its Help Desk.

        Microsoft Service Request       Service: MSR

            Microsoft offers the Service Request System as an optional,
            private (fee-based per incident) technical support service
            that offers to help solve complex development problems.
            Other avenues, such as the Microsoft Developer Support
            Forums and Microsoft Developer Knowlede Base, should be
            consulted prior to using the Service Request System.

        Microsoft Software Library      Service: MSL

            The Microsoft Software Library is a collection of uploaded
            binary files, samples, technical notes and utilities about
            various Microsoft programs.  The entire library is keyword
            searchable and the files can easily be downloaded to your
            computer.

        Microsoft Windows SDK Forum     Service: WINSDK

            Developers using the Windows Software Development Kit [and
            DDK] will want to take advantage of the community of
            assistance and support available in the Windows SDK Forum.
            Help is available for subjects such as tools, accelerators,
            controls, dialogue boxes, memory management, fonts,
            palettes and color [and device drivers].

12.  What other information is available?

    The October 1992 Microsoft Windows NT Device Driver Developer's
    Conference video/audio tapes are still available. Contact:

          MobileTape Co. Inc.
          address: 25061 W. Stanford, Suite 70; Valencia, CA 91355, USA
          phone (orders): 800.369.5718
          phone (info): 805.295.0504
          fax: [phone]

        ask for the order form for the event:

          Microsoft Windows NT Device Driver Developer's Conference
          October 26-28, 1992
          Anaheim, CA

    Solomon Software Technologies
    20 Hunters Lante
    Nashua, NH 03063-2245
    USA
    Phone: [phone]
    Phone: [phone]
    FAX: [phone]
    Email: [e-mail]

        They offer various technical seminars by folks such as Richard Hale
        Shaw, Jamie Hanrahan, Jeffrey Richter, and David Solomon. Topics
        include Visual C++, OLE, MFC, Windows '95 ("Chicago"), Win32
        programming, and Windows NT device drivers. One relevant seminar
        is "Windows NT Kernel-Mode Device Driver Programming".


99.  Conflict of interest?

    The editor works for Vireo Software, Inc. and is one
    of the authors of the VtoolsD VxD toolkit mentioned
    in this document.  I hope you find the information listed
    here to be useful.  Please send comments, suggestions,
    questions, etc.

    -- Steve Lewin-Berlin
       Vireo Software
       [e-mail]