139 lines
4.1 KiB
Groff
139 lines
4.1 KiB
Groff
.\" $NetBSD: edid.9,v 1.2 2006/12/23 06:36:19 wiz Exp $
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.\"
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.\" Copyright 2006 Itronix Inc.
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.\" All rights reserved.
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.\"
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.\" Written by Garrett D'Amore for Itronix Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The name of Intronix Inc. may not be used to endorse
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.\" or promote products derived from this software without specific prior
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.\" written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY INTRONIX INC. ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ITRONIX INC. BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd May 11, 2006
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.Dt EDID 9
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.Os
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.Sh NAME
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.Nm edid
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.Nd VESA Extended Display Identification Data
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.Sh SYNOPSIS
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.In dev/videomode/edidvar.h
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.In dev/videomode/edidreg.h
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.Ft int
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.Fo edid_is_valid
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.Fa "uint8_t *data"
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.Fc
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.Ft int
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.Fo edid_parse
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.Fa "uint8_t *data"
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.Fa "struct edid_info *info"
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.Fc
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.Ft void
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.Fo edid_print
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.Fa "struct edid_info *info"
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.Fc
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.Sh DESCRIPTION
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These
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functions provide support parsing the Extended Display Identification Data
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which describes a display device such as a monitor or flat panel display.
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.Pp
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The
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.Fn edid_is_valid
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function simply tests if the EDID block in
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.Fa data
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contains valid data. This test includes a verification of the checksum,
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and that valid vendor and product idenfication data is present. The data
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block contain at least 128 bytes.
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.Pp
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The
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.Fn edid_parse
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function parses the supplied
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.Fa data
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block (which again, must be at least 128 bytes), writing the relevant
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data into the structure pointed to by
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.Fa info .
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.Pp
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The
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.Fn edid_print
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function prints the data in the given
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.Fa info
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structure to the console device.
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.Pp
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.\" XXX
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.\" XXX It sure would be nice to have documentation about the details of the
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.\" XXX edid_info structure itself. This takes more time, though, and
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.\" XXX hopefully someone else will write it up. In the meantime, the code
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.\" XXX references should be useful.
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.\" XXX
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.Sh RETURN VALUES
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The
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.Fn edid_is_valid
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function returns 0 if the data block is valid, and
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.Er EINVAL
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otherwise.
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The
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.Fn edid_parse
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function returns zero if the data was successfully parsed, and
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non-zero otherwise.
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.Sh CODE REFERENCES
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This section describes places within the
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.Nx
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source tree where actual code implementing or using the
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EDID subsystem can be found.
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All pathnames are relative to
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.Pa /usr/src .
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.Pp
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The EDID subsystem is implemented within the file
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.Pa sys/dev/videomode/edid.c .
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.Pp
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The EDID subsystem also makes use of VESA Generalized Timing Formula located
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located in
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.Pa sys/dev/videomode/vesagtf.c
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and the generic videomode database located in
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.Pa sys/dev/videomode/videomode.c .
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.Sh EXAMPLES
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The following code uses these functions
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to retrieve and print information about a monitor:
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.Pp
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.Bd -literal -compact
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struct edid_info info;
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i2c_tag_t tag;
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char buffer[128];
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...
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/* initialize i2c tag... */
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...
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if ((ddc_read_edid(tag, buffer, 128) == 0) &&
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(edid_parse(buffer, &info) == 0))
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edid_print(info);
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...
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.Ed
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.Sh SEE ALSO
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.Xr ddc 9 ,
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.Xr edid 9 ,
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.Xr iic 9
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.Sh HISTORY
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These routines were added in
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.Nx 4.0 .
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.Sh AUTHORS
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.An Garrett D'Amore Aq gdamore@NetBSD.org
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