NAME

edid — VESA Extended Display Identification Data

SYNOPSIS

#include <dev/videomode/edidvar.h>
#include <dev/videomode/edidreg.h>

int
edid_is_valid(uint8_t *data);

int
edid_parse(uint8_t *data, struct edid_info *info);

void
edid_print(struct edid_info *info);

DESCRIPTION

These functions provide support parsing the Extended Display Identification Data which describes a display device such as a monitor or flat panel display.

The edid_is_valid() function simply tests if the EDID block in data contains valid data. This test includes a verification of the checksum, and that valid vendor and product idenfication data is present. The data block contain at least 128 bytes.

The edid_parse() function parses the supplied data block (which again, must be at least 128 bytes), writing the relevant data into the structure pointed to by info.

The edid_print() function prints the data in the given info structure to the console device.

RETURN VALUES

The edid_is_valid() function returns 0 if the data block is valid, and EINVAL otherwise. The edid_parse() function returns zero if the data was successfully parsed, and non-zero otherwise.

CODE REFERENCES

The EDID subsystem is implemented within the file sys/dev/videomode/edid.c.

The EDID subsystem also makes use of VESA Generalized Timing Formula located located in sys/dev/videomode/vesagtf.c and the generic videomode database located in sys/dev/videomode/videomode.c.

EXAMPLES

The following code uses these functions to retrieve and print information about a monitor:

	struct edid_info info; 
	i2c_tag_t        tag; 
	char		 buffer[128]; 
 
	... 
	/* initialize i2c tag... */ 
	... 
	if ((ddc_read_edid(tag, buffer, 128) == 0) && 
	    (edid_parse(buffer, &info) == 0)) 
		edid_print(info); 
	...

SEE ALSO

ddc(9), iic(9)

HISTORY

These routines were added in NetBSD 4.0.

AUTHORS

Garrett D'Amore <gdamore@NetBSD.org>