path: root/docs/The KDrive Tiny X Server.txt

                            The KDrive Tiny X Server

   This page is obsolete; the howto information contained herein does not
   apply to recent X.Org releases. It may still be of interest if you want
   to understand what KDrive is about.

   KDrive (Tiny X, TinyX) is an X server written by Keith Packard that was
   designed for low memory environments. On Linux/x86, a KDrive server
   with RENDER support but without support for scalable fonts compiles
   into less than 700 KB of text. KDrive tends to avoid large memory
   allocations at runtime, and tries to perform operations "on the fly"
   whenever possible (but this is also true of recent versions of the
   stock XFree86 server).

   Unlike the usual XFree86 server, a KDrive server is completely
   self-contained: it does not require any configuration files, and will
   even function if no on-disk fonts are available. All configuration is
   done at compile time and through command-line flags.

   At the time of writing, KDrive is for Linux only, although it could
   probably be ported to other Unix-like systems with little effort.

   Disclaimer: This text was written by an incompetent amateur (J.Ch.),
   and does not carry the imprimatur of Keith Packard. I am not intimately
   familiar with all of the KDrive code, and this document is probably
   wildly inaccurate. I am sole responsible for any errors or omissions in
   this document.

   The information contained herein is offered in good faith, but with no
   warranty of any kind. No kidding.

The Xfbdev KDrive server

   The default KDrive server, Xfbdev, is designed for a Linux installation
   with a working /dev/fb and any common PC mouse on /dev/mouse. It
   includes the following drivers:
     * Linux OS support;
     * generic Linux keyboard;
     * generic mouse;
     * Linux fbdev display (unaccelerated).

   Xfbdev includes support for BDF and PCF bitmap fonts only. In addition,
   it hardwires a number of standard fonts, notably cursor and fixed,
   which will therefore be available even when there are no on-disk fonts.
   By default, it does not contain support for local scalable fonts in any
   format.

   Xfbdev also includes support for a number of server extensions,
   including the ubiquitous SHAPE and the soon-to-be ubiquitous RENDER.

   In order to compile Xfbdev, you need a clean XFree86 tree; I recommend
   version 4.0.2 or later. Put the following lines in your host.def file:

   #define BuildServersOnly YES
   #define KDriveXServer YES
   #define TinyXServer YES
   #define XfbdevServer YES

   Now make World as usual; if the compilation proceeds without errors,
   you should have an executable xc/programs/Xserver/Xfbdev.

   You may now make install or make install.man.

   For information on running the Xfbdev server, please see the
   [1]Xfbdev(1), [2]Xkdrive(1) and [3]Xserver(1) manual pages.

The Xvesa KDrive server

   The Xvesa server is for x86 hardware only, and includes an
   unaccelerated display driver that will support any card with a VESA,
   VGA or even EGA BIOS (VESA 1.1 is the earliest supported version;
   VESA 2.0 will give better performance). Except for the display driver,
   the Xvesa server is identical to Xfbdev.

   Unless you're using an original Hercules Graphics chipset or
   compatible, your hardware is most probably supported. In addition, the
   video driver in Xvesa will automagically do any initialisation of your
   chipset that your BIOS knows about but that might be undocumented, and
   thus not present in the stock XFree86 drivers. Xvesa is therefore an
   excellent choice for laptops, and until recently I was using Xvesa as
   the primary X server on mine.

   God protect us from copper money and CGA cards.

   In order to build the Xvesa server, include the following lines in your
   host.def file:

   #define BuildServersOnly YES
   #define KDriveXServer YES
   #define TinyXServer YES
   #define XvesaServer YES

   For information on running the Xvesa server, please see the
   [4]Xvesa(1), [5]Xkdrive(1) and [6]Xserver(1) manual pages.

Other standard KDrive servers

   The KDrive makefiles include building recipes for a number of other
   servers, some of which use accelerated display drivers. These servers
   are not currently documented.

   Any volunteers?

   Fore more information, please see the [7]Xkdrive(1) manual page and the
   file [8]xc/config/cf/kdrive.cf.

Custom KDrive servers

   A KDrive server does not include multiple drivers. In order to run
   KDrive on your hardware, you need to compile a KDrive server with the
   proper os, keyboard, mouse and display drivers. In addition, you will
   need to select the set of font renderers and server extensions that you
   want to compile.

  OS support

   At the time of writing, the publicly-available KDrive server only
   supports Linux. As most of KDrive is OS-agnostic, porting to a
   different Unix-like system should not be difficult.

   Some bits of the source hint at support for certain proprietary
   systems, but it seems incomplete.

   If you port KDrive to a different OS, I'd be glad to hear from you (and
   I am sure so would Keith). BSD should be easy. Minix-VMD might be more
   challenging, as it lacks a standard socket library; but then, earlier
   versions of XFree86 used to run on Minix-VMD, and KDrive uses the same
   XTrans layer. Stock 32-bit Minix doesn't have a poll/select equivalent.

   I want to see KDrive on stock Minix. Please.

  Keyboard support

   At the time of writing, the KDrive server only has support for a
   generic Linux keyboard; the keyboard mapping is copied from the Linux
   kernel tables at startup. As X11 has richer keyboard information than
   Linux, and furthermore KDrive's mapping tables are incomplete, the
   results are not always perfect; I have found it necessary to fix my
   keyboard using xmodmap.

  Mouse support

   Since XFree86 4.2.0, KDrive automatically detects the type of mouse on
   /dev/mouse, which should be a link to the correct mouse device. Most
   common types of mice (including, of course, PS/2, Microsoft and
   Logitech serial, and Microsoft "bus") are supported by the mouse
   driver; if yours is not, your best bet is probably to use gmp in
   repeater mode.

  Display drivers

   KDrive includes a fairly large selection of display drivers. Two are
   fully generic but unaccelerated: fbdev (included in the Xfbdev server)
   and vesa (included in the Xvesa server). The other drivers are
   partially accelerated, and support specific video hardware.

   The generic drivers are documented in the [9]Xfbdev(1) and [10]Xvesa(1)
   manual pages. The accelerated drivers are currently undocumented; the
   only source of information about them is the source. Please see the
   directories under hw/kdrive/ and enjoy your read.

  Font renderers

   KDrive should be able to support all the font renderers supported by
   XFree86. You may add any of the following to your host.def file:

   #define BuildSpeedo YES
   #define BuildType1 YES
   #define BuildCID YES
   #define BuildFreeType YES
   #define FontServerAccess YES

   In XFree86 4.3.0 and later, the FreeType backend includes support for
   all common scalable font formats (including Type 1). For most uses, it
   is the only one that you will need.

   Some of these renderers are rather large; you may want to think twice
   before including them in your "tiny" server.

   As noted above, KDrive includes a number of hardwired, compiled-in
   fonts. There is no good reason to disable support for these "built-in"
   fonts; however, if you insist, you may use

   #define BuildBuiltinFonts NO

  Server extensions

   KDrive might or might not be able to support any server extension
   supported by XFree86 that is not directly related to hardware. Use the
   usual incantations in your host.def file, for example,

   #define BuildDBE YES

   There is no good reason to disable the RENDER extension.

  Additional defines

   Any additional options that you want to pass to the C compiler should
   be put in KdriveServerExtraDefines:

   #define KdriveServerExtraDefines -DPIXPRIV

Building against uClibc

   At least the Xvesa server appears to build and run when linked against
   [11]uClibc; note, however, that I haven't done any extensive testing.

   You will first need to add two trivial functions to uClibc; this is
   simply done by relinking uClibc with [12]uclibc-missing-math.c. Then,
   assuming that your uclibc toolchain is invoked by i386-uclibc-cc, add
   the following to your host.def file:

   #define CcCmd i386-uclibc-cc

   If you haven't recompiled libz against uClibc, you will also need to
   add the following line to your host.def:

   #define HasZlib NO

   This will have the side-effect of disabling all support for compressed
   fonts.

   Is the uclibc-missing-math.c hack still necessary with recent uClibc
   releases?

Download

   Binary KDrive servers for GNU/Linux/x86 might be available from [13]my
   KDrive download directory.

   These binaries are offered in good faith, but really with no guarantee.
   Not even of any kind.

References

   [14]Handhelds Org and Jim Gettys' page about [15]cross-compiling
   KDrive.

   [16]Keith Packard, the primary author of KDrive.

   [17]Back to my software page.

   [18]Juliusz Chroboczek, <jch@pps.jussieu.fr>

References

   1. http://www.xfree86.org/current/Xfbdev.1.html
   2. http://www.xfree86.org/current/Xkdrive.1.html
   3. http://www.xfree86.org/current/Xserver.1.html
   4. http://www.xfree86.org/current/Xvesa.1.html
   5. http://www.xfree86.org/current/Xkdrive.1.html
   6. http://www.xfree86.org/current/Xserver.1.html
   7. http://www.xfree86.org/current/Xkdrive.1.html
   8. http://cvsweb.xfree86.org/cvsweb/xc/config/cf/kdrive.cf
   9. http://www.xfree86.org/current/Xfbdev.1.html
  10. http://www.xfree86.org/current/Xvesa.1.html
  11. http://www.uclibc.org/
  12. https://www.pps.jussieu.fr/~jch/software/uclibc-missing-math.c
  13. https://www.pps.jussieu.fr/~jch/software/kdrive/
  14. http://www.handhelds.org/
  15. http://www.handhelds.org/minihowto/building-x.html
  16. http://www.keithp.com/
  17. https://www.irif.univ-paris-diderot.fr/~jch/software/
  18. https://www.irif.univ-paris-diderot.fr/~jch/