plan9fox/sys/man/6/vgadb

.TH VGADB 6
.SH NAME
vgadb \- VGA controller and monitor database
.SH DESCRIPTION
.PP
The VGA database,
.BR /lib/vgadb ,
consists of two parts,
the first describing how to identify and program a VGA controller
and the second describing the timing parameters for known 
monitors to be loaded into a VGA controller to give a particular
resolution and refresh rate.
Conventionally, at system boot, the program
.B aux/vga
(see
.IR vga (8))
uses the monitor type in 
.BR /env/monitor ,
the display resolution in
.BR /env/vgasize ,
and the VGA controller information in the database to
find a matching monitor entry and initialize the VGA controller accordingly.
.PP
The file comprises multi-line entries made up of
attribute/value pairs of the form
.IB attr = value
or sometimes just
.IR attr .
Each line starting without white space starts a new entry.
Lines starting with
.B #
are comments.
.PP
The first part of the database, the VGA controller identification and
programming information,
consists of a number of entries with attribute
.B ctlr
and no value.
Within one of these entries the following attributes are
meaningful:
.TF 0xC0000
.TP
.I nnnnn
an offset into the VGA BIOS area.
The value is a string expected to be found there that will
identify the controller.
For example,
.B 0xC0068="#9GXE64 Pro"
would identify a #9GXEpro VGA controller if the string
.B "#9GXE64 Pro"
was found in the BIOS at address 0xC0068.
There may be more than one identifier attribute per controller.
If a match cannot be found, the first few bytes of the BIOS
are printed to help identify the card and create a controller
entry.
.TP
.IB nnnnn - mmmmm
A range of the VGA BIOS area.
The value is a string as above, but the entire range
is searched for that string.
The string must begin at or after
.I nnnnn
and not contain any characters at or after
.IR mmmmm .
For example,
.B 0xC0000-0xC0200="MACH64LP"
identifies a Mach 64 controller with the
string 
.B MACH64LP
occurring anywhere in the first 512 bytes of BIOS memory.
.TP
.B ctlr
VGA controller chip type.
This must match one of the VGA controller types
known to
.B /dev/vgactl
(see
.IR vga (3))
and internally to
.BR aux/vga .
Currently,
.BR ark2000pv ,
.BR clgd542x ,
.BR ct65540 ,
.BR ct65545 ,
.BR cyber938x ,
.BR et4000 ,
.BR hiqvideo ,
.BR ibm8514 ,
.BR mach32 ,
.BR mach64 ,
.BR mach64xx ,
.BR mga2164w ,
.BR neomagic ,
.BR s3801 ,
.BR s3805 ,
.BR s3928 ,
.BR t2r4 ,
.BR trio64 ,
.BR virge ,
.BR vision864 ,
.BR vision964 ,
.BR vision968 ,
and
.B w30c516
are recognized.
.TP
.B ramdac
RAMDAC controller type.
This must match one of the types
known internally to
.BR aux/vga .
Currently
.BR att20c490 ,
.BR att20c491 ,
.BR att20c492 ,
.BR att21c498 ,
.BR bt485 ,
.BR rgb524mn ,
.BR sc15025 ,
.BR stg1702 ,
.BR tvp3020 ,
.BR tvp3025 ,
and
.B tvp3026
are recognized.
.TP
.B clock
clock generator type.
This must match one of the types
known internally to
.BR aux/vga .
Currently
.BR ch9294 ,
.BR icd2061a ,
.BR ics2494 ,
.BR ics2494a ,
.BR s3clock ,
.BR tvp3025clock ,
and
.B tvp3026clock
are recognized.
.TP
.B hwgc
hardware graphics cursor type.
This must match one of the types
known to
.B /dev/vgactl
and internally to
.BR aux/vga .
Currently
.BR ark200pvhwgc ,
.BR bt485hwgc ,
.BR clgd542xhwgc ,
.BR clgd546xhwgc ,
.BR ct65545hwgc ,
.BR cyber938xhwgc ,
.BR hiqvideohwgc ,
.BR mach64xxhwgc ,
.BR mga2164whwgc ,
.BR neomagichwgc ,
.BR rgb524hwgc ,
.BR s3hwgc ,
.BR t2r4hwgc ,
.BR tvp3020hwgc ,
and
.B tvp3026hwgc
are recognized.
.TP
.B membw
Memory bandwidth in megabytes per second.
.I Vga
chooses the highest refresh rate possible within the constraints
of the monitor (explained below) and the
card's memory bandwidth.
.TP
.B linear
Whether the card supports a large (>64kb) linear memory
window.  The value is either
.B 1
or
.B 0
(equivalent to unspecified).
The current kernel graphics subsystem
requires a linear window; entries without
.B linear=1
are of historic value only.
.TP
.B link
This must match one of the types
known internally to
.BR aux/vga .
Currently
.B vga
and
.B ibm8514
are recognized.
The type
.B vga
handles generic VGA functions and should almost always be included.
The type
.B Ibm8514
handles basic graphics accelerator initialization on controllers
such as the early S3 family of GUI chips.
.PD
.PP
The
.BR clock ,
.BR ctlr ,
.BR link ,
and
.B ramdac
values can all take an extension following a
.B '-'
that can be used as a speed-grade
or subtype; matching is done without the extension.
For example,
.B ramdac=stg1702-135
indicates the STG1702 RAMDAC has a maximum clock frequency of 135MHz,
and
.B clock=ics2494a-324
indicates that the frequency table numbered
324
should be used for the ICS2494A clock generator.
.PP
The functions internal to
.B aux/vga
corresponding to the
.BR clock ,
.BR ctlr ,
.BR link ,
and
.B ramdac
values will be called in the order given for initialization.
Sometimes the clock should be set before the RAMDAC is initialized,
for example, depending on the components used.
In general,
.BR link=vga
will always be first and,
if appropriate,
.BR link=ibm8514
will be last.
.PP
The entries in the second part of
.B /lib/vgadb
have as attribute the name of a monitor type
and the value is conventionally a resolution in the form
.IB X x Y\f1,
where
.I X
and
.I Y
are numbers representing width and height in pixels.
The monitor type (i.e. entry)
.B include
has special properties, described below and shown in the examples.
The remainder of the entry contains timing information for
the desired resolution.
Within one of these entries the following attributes are
meaningful:
.TF interlace
.TP
.B clock
the video dot-clock frequency in MHz required for this resolution.
The value 25.175 is known internally to
.IR vga (8)
as the baseline VGA clock rate.
.B defaultclock
the default video dot-clock frequency in MHz used
for this resolution when no
memory bandwidth is specified for the card
or when
.I vga
cannot determine the maximum clock frequency of the card.
.TP
.B shb
start horizontal blanking, in character clocks.
.TP
.B ehb
end horizontal blanking, in character clocks.
.TP
.B ht
horizontal total, in character clocks.
.TP
.B vrs
vertical refresh start, in character clocks.
.TP
.B vre
vertical refresh end, in character clocks.
.TP
.B vt
vertical total, in character clocks.
.TP
.B hsync
horizontal sync polarity.
Value must be
.B +
or
.BR - .
.TP
.B vsync
vertical sync polarity.
Value must be
.B +
or
.BR - .
.TP
.B interlace
interlaced mode.
Only value
.B v
is recognized.
.TP
.B alias
continue, replacing the
.B alias
line by the contents of the entry whose attribute is given as
.IR value .
.TP
.B include
continue, replacing this
.B include
line by the contents of the previously defined
.B include
monitor type with matching
.IR value .
(See the examples.)
Any non-zero attributes already set will not be overwritten.
This is used to save duplication of timing information.
Note that
.I value
is not parsed, it is only used as a string
to identify the previous
.BI include= value
monitor type entry.
.PD
.PP
The values given for
.BR shb ,
.BR ehb ,
.BR ht ,
.BR vrs ,
.BR vre ,
.BR vt ,
.BR hsync ,
and
.B vsync
are beyond the
scope of this manual page.
See the book by
Ferraro
for details.
.SH EXAMPLES
Basic
.B ctlr
entry for a laptop with a Chips and Technology 65550 
controller:
.EX
ctlr                        # NEC Versa 6030X/6200MX
    0xC0090="CHIPS 65550 PCI & VL Accelerated VGA BIOS"	
    link=vga
    ctlr=hiqvideo linear=1
    hwgc=hiqvideohwgc
.EE
A more complex entry. Note the extensions on the
.BR clock ,
.BR ctlr ,
and
.B ramdac
attributes. The order here is important: the RAMDAC clock input must be
initialized before the RAMDAC itself. The clock frequency is selected by
the
.B ET4000
chip.
.EX
ctlr						# Hercules Dynamite Power
    0xC0076="Tseng Laboratories, Inc. 03/04/94 V8.00N"
    link=vga
    clock=ics2494a-324
    ctlr=et4000-w32p
    ramdac=stg1702-135
.EE
Monitor entry for type
.B vga
(the default monitor type used by
.IR vga (8))
and resolution 640x480x[18].
.EX
include = 640x480@60Hz				# 60Hz, 31.5KHz
    clock=25.175
    shb=664 ehb=760 ht=800
    vrs=491 vre=493 vt=525

vga = 640x480					# 60Hz, 31.5KHz
    include=640x480@60Hz
.EE
Entries for multisync monitors with video bandwidth up to 65MHz.
.EX
#
# Multisync monitors with video bandwidth up to 65MHz.
#
multisync65 = 1024x768        # 60Hz, 48.4KHz
    include=1024x768@60Hz
multisync65 = 1024x768i       # 87Hz, 35.5KHz (interlaced)
    include=1024x768i@87Hz
multisync65
    alias=vga
.EE
Note how this builds on the existing
.B vga
entries.
.SH FILES
.TP
.B /lib/vgadb
.SH "SEE ALSO"
.IR ndb (2),
.IR vga (3),
.IR ndb (6),
.IR vga (8)
.br
Richard E. Ferraro,
.I
Programming Guide to the EGA, VGA and Super VGA Cards,
Third Edition
.SH BUGS
The database should provide a way
to use the PCI bus
as well as BIOS memory to identify cards.
.SH "ADDING A NEW MONITOR"
Adding a new monitor is usually fairly straightforward, as most modern monitors
are multisync and the only interesting parameter is the
maximum video bandwidth.
Once the timing parameters are worked out for a particular maximum
video bandwidth as in the example above, an entry for a new monitor
with that limit is simply
.EX
#
# Sony CPD-1304
# Horizontal timing:
#	Allowable frequency range: 28-50KHz
# Vertical timing:
#	Allowable frequency range: 50-87Hz
#
cpd-1304
	alias=multisync65
.EE
Even this is not necessary, as the monitor type could simply be
given as
.BR multisync65 .
.SH "ADDING A NEW VGA CONTROLLER"
While the use of this database formalizes the steps needed to
program a VGA controller,
unless you are lucky and all the important components on
a new VGA controller card are interconnected in the same way as an
existing entry, adding a new entry requires adding new internal
types to
.IR vga (8).
Fortunately, the unit of variety 
has, for the most part, shifted from
individual components to entire
video chipsets.
Thus in lucky cases all that is necessary
is the addition of another
.B 0xNNNNN=
line to the entry for the controller.
This is particularly true in the case
of the ATI Mach 64 and the S3 Virge.
.PP
If you need to actually add support
for a controller with a different chipset,
you will need the data sheets for the VGA controller
as well as any RAMDAC or clock generator
(these are commonly integrated into the controller).
You will also need to know how these components interact.
For example, a common combination is an S3 86C928 VGA chip with
an ICD2061A clock generator. The ICD2061A is usually loaded by clocking
a serial bit-stream out of one of the 86C928 registers.
Similarly, the RAMDAC may have an internal clock-doubler and/or
pixel-multiplexing modes, in which case both the clock generator and
VGA chip must be programmed accordingly.
Hardware acceleration for rectangle fills
and block copies is provided in the kernel;
writing code to handle this is necessary
to achieve reasonable performance at high
pixel depths.