.TH vga_setlinearaddressing 3 "27 July 1997" "Svgalib (>= 1.2.11)" "Svgalib User Manual"
.SH NAME
vga_setlinearaddressing \- switch to linear addressing mode
.SH SYNOPSIS

.B "#include <vga.h>"

.BI "int vga_setlinearaddressing(void);"

.SH DESCRIPTION
Switch to linear addressing mode. This maps all (or most) of the SVGA memory at the
position returned by
.BR vga_getgraphmem (3)
(which will probably change by the call
to
.BR vga_setlinearaddressing()).
The
.BR vga_set*page (3)
calls
are no longer required. This ensures optimal performance, however, 
not all cards support it (and not in all modes).

Use
.BR vga_modeinfo (3)
to check for availability of the function in a given mode.

Furthermore, some cards (Cirrus) just enable this buffer at a fixed hardware address.
For Cirrus it is mapped at 14MB so you should never used it if you have more than 14MB
of memory (But how does an application know?).
The Mach32 support for this is smarter. It makes this feature only available when it is safe
to be used.

To avoid all this problems you can use

.TP
.B nolinear
Inhibit use of a linear mmaped frame buffer.
.TP
.B linear
Allow (not enforce!) use of a linear mmaped frame buffer.
.P
in the
.I /etc/vga/libvga.config
file to disable the linear frame buffer if it cannot be used.

Returns the size of the mapped framebuffer if successful (can
be less than total video memory), -1 if not.

The
.BR testlinear (6)
demo shows the use of this feature (and if it works for you).
.SH SEE ALSO

.BR svgalib (7),
.BR vgagl (7),
.BR libvga.config (5),
.BR testlinear (6),
.BR vga_modeinfo (3),
.BR vga_getgraphmem (3),
.BR vga_setpage (3),
.BR vga_setreadpage (3),
.BR vga_setwritepage (3),
.BR vga_setlinearaddressing (3)

.SH AUTHOR

This manual page was edited by Michael Weller <eowmob@exp-math.uni-essen.de>. The
exact source of the referenced function as well as of the original documentation is
unknown.

It is very likely that both are at least to some extent are due to
Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.

Occasionally this might be wrong. I hereby
asked to be excused by the original author and will happily accept any additions or corrections
to this first version of the svgalib manual.