Felisp
84436a5ae0
http://my.svgalib.org/svgalib/svgalib-1.9.25.tar.gz http://my.svgalib.org/svgalib/
140 lines
4.9 KiB
Text
140 lines
4.9 KiB
Text
Patching svgalib
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Contents
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0. Introduction
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1. Indenting
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2. Structure of the chipset drivers
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0. Introduction
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Here is some info on writing patches and/or adding support for
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further chipsets. The info on the chipset drivers is outdated, but
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better than nothing and get you started.
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As a side note, other than a.out, ELF does not allow to have some
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symbols global to svgalib which are not accessible to user
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programs.
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Because of that, if possible all the symbols and functions in your
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program should be static. Those which can not be static should
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have a name like: "__svgalib_*" to mark them as internals s.t.
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people using them get what they deserve. Please do only add a new
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function to the user interface if it is really unavoidable. Better
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add some new parameters to an existing function.
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Adding a new function would definitly result in loosing a.out
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compatibility thus removing the chance to use new cards and such
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with old a.out binaries where the source is not available (doom
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comes to mind).
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A new function should be really important to outweigh this draw
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back.
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1. Indenting
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Due to some request (and I heard it b4) all the sources were now
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automatically indentified.
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There were some requests for indent -gnu but it looks painful. I
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opted for -kr (there were requests for it as well) as it is not
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only nicer but also what is done in the linux-kernel and this is
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certainly a program only usable for linux.
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I dunno if emacs is confused by -kr, but to be honest this is a
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big all-in-one egg-giving-wool-milk-sow (as we say in german), and
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you won't tell me that this several megs beast is unable to edit
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this and I can't use -kr due to some restrictions of emacs. That
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would be really ridiculous. If it is the case just make emacs
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better.
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The OneModeEntry macro is eaten by indent (I would say it is an
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indent bug, I might send a bug report to them), please ensure (if
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at all possible) that your code can be passed through indent (use
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the INDENT-OFF comments as shown in some sources for
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OneModeEntry).
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You can use `make indent-gnu' (if you have a recent enough (I use
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1.9.1) indent) to switch to your favorite style. But please ensure
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your patches fit into this now declared as "official style"
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sources. (Use `make indent' to reformat).
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Do not use it too often though as most indent's tend to add empty
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lines at certain places in the source.
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2. Structure of the chipset drivers
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The chipset specific registers saving function (saveregs) is only
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used directly to save the textmode registers at initialization.
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The chipset specific registers restoring function (setregs) is only
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used directly to return to textmode, and when setting a VGA mode
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after an SVGA mode.
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The registers for each mode are stored like the ET4000 modes in
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VGAlib 1.2, i.e. the extended registers at the end. The following
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functions must be provided in a driver:
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saveregs( unsigned char regs[] )
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Saves the chipset-specific registers in regs, starting at
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array index EXT (after the VGA registers).
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setregs( unsigned char regs[] )
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Sets the chipset-specific registers stored in regs from
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index EXT.
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modeavailable( int mode )
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Returns nonzero if mode is available (should check video
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memory).
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getmodeinfo( vga_modeinfo *modeinfo )
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Fills in chipset specific field of mode information
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structure: maxlogicalwidth, startaddressrange (mask of
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significant bits), and maxpixels (video memory divided by
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the number of bytes per pixel). haveblit indicates whether
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bitblt functions are available.
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Note: providing extended info and an aperture with size
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>= memory and setting bits 4 and 6 in flags will
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automatically enable linear addressing support.
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setmode( int mode, int previous_mode )
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Sets all registers for a mode; returns nonzero if mode not
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available. __vga_setregs can be called to set the VGA
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registers.
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unlock()
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Unlocks chipset-specific registers.
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lock()
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Lock (protect) chipset-specific registers. Currently not
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called.
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test()
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Identify chipset; initialize (check memory and type) and
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return nonzero if detected.
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setpage( int page )
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Set 64K page number to be mapped at 0xa0000.
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init( int force, int par1, ... )
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Initialize memory and type; called by test. If force is 1,
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the chiptype or the amount of memory can be forced (this
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is pretty useless).
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The following functions provide for things like page flipping
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and hardware scrolling virtual desktops.
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setdisplaystart( int address )
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Sets the display start address in video memory in pixels.
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setlogicalwidth( int width )
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Sets the logical scanline length in bytes. Usually a
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multiple of 8.
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The function getchipset() in vga.c must call the test routine for
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the chipset. The chipsetfunctionslist must be have a pointer
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to the chipsetfunctions table for the chipset (which is the only
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global symbol in a chipset driver). Also, vga.h contains a magic
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number for each chipset. Also driver_names[] in vga.c has to
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contain a name for each driver at the correct position.
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