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NetBSD 6.1.5 - man page for ddc (netbsd section 9)

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

     ddc -- VESA Display Data Channel V2

     #include <dev/i2c/ddcvar.h>

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

     The ddc_read_edid() reads a VESA Extended Display Identification Data block (EDID) via VESA
     Display Data Channel (DDCv2).  DDCv2 is a protocol 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.

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

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

     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))

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

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

     DDCv2 support was added in NetBSD 4.0.

     Garrett D'Amore <gdamore@NetBSD.org>

BSD					   May 11, 2006 				      BSD
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