Kernel driver `ddcmon.o'
========================

Status: Beta

Supported chips:
  * Any DDC Monitor EDID EEPROM chip at 0x50
    Prefix `ddcmon'
    Addresses scanned: I2C 0x50
    Standards: available for purchase from VESA http://www.vesa.org
    Datasheets: Publicly available from Atmel (www.atmel.com),
                Fairchild (www.fairchildsemi.com), and
                Microchip (www.microchip.com)

	Chip	Size (bits)	Address
	24C01	 1K		0x50 (shadows at 0x51 - 0x57)
		 		     (Typical device in monitors)
	24C01A	 1K		0x50 - 0x57 (Typical device in monitors)
	24C02	 2K		0x50 - 0x57
	24C04	 4K		0x50, 0x52, 0x54, 0x56
				(additional data at 0x51, 0x53, 0x55, 0x57)
	24C08	 8K		0x50, 0x54 (additional data at 0x51, 0x52,
				0x53, 0x55, 0x56, 0x57)
	24C16	16K		0x50 (additional data at 0x51 - 0x57)


Authors: Frodo Looijaard <frodol@dds.nl>, Philip Edelbrock <phil@netroedge.com>,
        and Mark Studebaker <mdsxyz123@yahoo.com>

Special assistance on DDC provided by Petr Vandrovec <vandrove@vc.cvut.cz>

Module Parameters
-----------------

* force: short array (min = 1, max = 48)
  List of adapter,address pairs to boldly assume to be present
* force_ddcmon: short array (min = 1, max = 48)
  Same as 'force'
* ignore: short array (min = 1, max = 48)
  List of adapter,address pairs not to scan
* ignore_range: short array (min = 1, max = 48)
  List of adapter,start-addr,end-addr triples not to scan
* probe: short array (min = 1, max = 48)
  List of adapter,address pairs to scan additionally
* probe_range: short array (min = 1, max = 48)
  List of adapter,start-addr,end-addr triples to scan additionally


Description
-----------

This is a simple module for reading the EEPROM on a DDC-compliant monitor.
DDC (Display Data Channel) is the I2C-based communication channel
to the monitor. The EEPROM contains a 128-byte data structure defined
by the EDID (Extended Display Identification Data) standard.

Use:

After inserting the module (and any other required smbus/i2c modules), you
should have a directory in /proc/sys/dev/sensors/ with a name such
as "ddcmon-i2c-3-50".  Inside each of these is a series of files which
represent interesting data from the DDC monitor.

/proc entries:

	ID: Encoded Monitor ID string.
		For encoding, see 'sensors'
		source ../../prog/sensors/chips.c.

	serial: 1 integer
		serial number

	size: 2 integers
		vertical monitor size (cm)
		horizontal monitor size (cm)

	sync: 4 integers
		minimum vertical sync frequency (Hz)
		maximum vertical sync frequency (Hz)
		minimum horizontal sync frequency (KHz)
		maximum horizontal sync frequency (KHz)

	timings: supported timings (bitmask)
		0x000001 720x400@70Hz (VGA 640x400, IBM)
		0x000002 720x400@88Hz (XGA2)
		0x000004 640x480@60Hz (VGA)
		0x000008 640x480@67Hz (Mac II, Apple)
		0x000010 640x480@72Hz (VESA)
		0x000020 640x480@75Hz (VESA)
		0x000040 800x600@56Hz (VESA)
		0x000080 800x600@60Hz (VESA)
		0x000100 800x600@72Hz (VESA)
		0x000200 800x600@75Hz (VESA)
		0x000400 832x624@75Hz (Mac II)
		0x000800 1024x768@87Hz interlaced (8514A)
		0x001000 1024x768@60Hz (VESA)
		0x002000 1024x768@70Hz (VESA)
		0x004000 1024x768@75Hz (VESA)
		0x008000 1280x1024@75Hz (VESA)
		0x010000 - 0x800000 Manufacturer reserved

Notes:

- The eeprom.o module will also attach to a DDC monitor. Install the
  ddcmon.o module before the eeprom.o module to prevent this.
  Alternatively, give the eeprom.o module an ignore= parameter or
  a checksum= parameter. The ddcmon.o module will not attach to non-DDC
  eeproms because it checks for a DDC 'signature' at the beginning
  of the DDC Monitor's eeprom.

- If a DDC monitor eeprom lacks the 'signature', you may use the
  'force' parameter (modprobe ddcmon force=x,0x50 where 'x' is the
  i2c bus number).

- This module requires a bus driver for your video chip to access the
  DDC bus. In this package, drivers exist for Voodoo3/Banshee chips.
  See documentation for those drivers in ../busses. Other drivers
  (Matrox and NVidia, for example) are available in the kernel or
  elsewhere. See our 'Supported Devices' web page for details.

- There is a checksum over the 128 bytes in the eeprom but the driver
  does not check it.

- More information is available in the eeprom which could be made
  available by enhancing the driver.
  To see the entire eeprom, use the eeprom.o module instead of ddcmon.o.
  However, then you lose the DDC-specific formatting.

- This driver does not support the DDC/CI (DDC2Bi) bidirectional
  communications channel to the monitor for controlling the monitor.

- The driver caches the data from the monitor and only rereads it
  from the eeprom if the cache is more than 5 minutes old.

- X 4.0 also accesses the DDC monitor EEPROM to auto-configure itself.
  There could possibly be conflicts from these multiple accesses.