netbsd man page for ddc

DDC(9)							   BSD Kernel Developer's Manual						    DDC(9)

NAME
     ddc -- VESA Display Data Channel V2

SYNOPSIS
     #include <dev/i2c/ddcvar.h>

     int
     ddc_read_edid(i2c_tag_t tag, uint8_t *dest, size_t len);

DESCRIPTION
     The ddc_read_edid() reads a VESA Extended Display Identification Data block (EDID) via VESA Display Data Channel (DDCv2).	DDCv2 is a proto-
     col for data exchange between display devices (such as monitors and flat panels) and host machines using an I2C bus.

     The tag argument is a machine-dependent tag used to specify the I2C bus on which the DDCv2 device is located.  The dest argument is a pointer
     to a buffer where the EDID data will be stored.  The len argument is the amount of data to read into the buffer.  (The buffer must be large
     enough.)  Typically, this value will be 128, which is the size of a normal EDID data block.

     Normally the EDID data block will be post-processed with the edid_parse() function.

RETURN VALUES
     The ddc_read_edid() function returns zero on success, and non-zero otherwise.

ENVIRONMENT
     The ddc_read_edid() function is part of the ddc(4) driver, and is only included in the kernel if that driver is also included.

EXAMPLES
     The following code uses ddc_read_edid() 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);
	     ...

     Note that this must be called before the PCI bus is attached during autoconfiguration.

SEE ALSO
     ddc(4), edid(9), iic(9)

HISTORY
     DDCv2 support was added in NetBSD 4.0.

AUTHORS
     Garrett D'Amore <gdamore@NetBSD.org>

BSD
								   May 11, 2006 							       BSD