ddc(9) - NetBSD Manual Pages

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

ddc -- VESA Display Data Channel V2
#include <dev/i2c/ddcvar.h> int 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 pan- els) 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 nor- mal 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 other- wise.
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.
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 auto- configuration.
ddc(4), edid(9), iic(9)
DDCv2 support was added in NetBSD 4.0.
Garrett D'Amore <gdamore@NetBSD.org> NetBSD 10.99 May 11, 2006 NetBSD 10.99
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