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Mark D. Studebaker
0a8aee470a
git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@1040 7894878c-1315-0410-8ee3-d5d059ff63e0
137 lines
4.7 KiB
Plaintext
137 lines
4.7 KiB
Plaintext
Kernel driver `ddcmon.o'
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========================
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Status: Beta
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Supported chips:
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* Any DDC Monitor EDID EEPROM chip at 0x50
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Prefix `ddcmon'
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Addresses scanned: I2C 0x50
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Standards: available for purchase from VESA http://www.vesa.org
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Datasheets: Publicly available from Atmel (www.atmel.com),
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Fairchild (www.fairchildsemi.com), and
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Microchip (www.microchip.com)
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Chip Size (bits) Address
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24C01 1K 0x50 (shadows at 0x51 - 0x57)
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(Typical device in monitors)
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24C01A 1K 0x50 - 0x57 (Typical device in monitors)
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24C02 2K 0x50 - 0x57
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24C04 4K 0x50, 0x52, 0x54, 0x56
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(additional data at 0x51, 0x53, 0x55, 0x57)
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24C08 8K 0x50, 0x54 (additional data at 0x51, 0x52,
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0x53, 0x55, 0x56, 0x57)
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24C16 16K 0x50 (additional data at 0x51 - 0x57)
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Authors: Frodo Looijaard <frodol@dds.nl>, Philip Edelbrock <phil@netroedge.com>,
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and Mark Studebaker <mdsxyz123@yahoo.com>
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Special assistance on DDC provided by Petr Vandrovec <vandrove@vc.cvut.cz>
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Module Parameters
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-----------------
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* force: short array (min = 1, max = 48)
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List of adapter,address pairs to boldly assume to be present
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* force_ddcmon: short array (min = 1, max = 48)
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Same as 'force'
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* ignore: short array (min = 1, max = 48)
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List of adapter,address pairs not to scan
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* ignore_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples not to scan
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* probe: short array (min = 1, max = 48)
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List of adapter,address pairs to scan additionally
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* probe_range: short array (min = 1, max = 48)
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List of adapter,start-addr,end-addr triples to scan additionally
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Description
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-----------
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This is a simple module for reading the EEPROM on a DDC-compliant monitor.
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DDC (Display Data Channel) is the I2C-based communication channel
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to the monitor. The EEPROM contains a 128-byte data structure defined
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by the EDID (Extended Display Identification Data) standard.
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Use:
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After inserting the module (and any other required smbus/i2c modules), you
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should have a directory in /proc/sys/dev/sensors/ with a name such
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as "ddcmon-i2c-3-50". Inside each of these is a series of files which
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represent interesting data from the DDC monitor.
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/proc entries:
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ID: Encoded Monitor ID string.
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For encoding, see 'sensors'
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source ../../prog/sensors/chips.c.
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serial: 1 integer
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serial number
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size: 2 integers
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vertical monitor size (cm)
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horizontal monitor size (cm)
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sync: 4 integers
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minimum vertical sync frequency (Hz)
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maximum vertical sync frequency (Hz)
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minimum horizontal sync frequency (KHz)
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maximum horizontal sync frequency (KHz)
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timings: supported timings (bitmask)
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0x000001 720x400@70Hz (VGA 640x400, IBM)
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0x000002 720x400@88Hz (XGA2)
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0x000004 640x480@60Hz (VGA)
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0x000008 640x480@67Hz (Mac II, Apple)
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0x000010 640x480@72Hz (VESA)
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0x000020 640x480@75Hz (VESA)
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0x000040 800x600@56Hz (VESA)
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0x000080 800x600@60Hz (VESA)
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0x000100 800x600@72Hz (VESA)
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0x000200 800x600@75Hz (VESA)
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0x000400 832x624@75Hz (Mac II)
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0x000800 1024x768@87Hz interlaced (8514A)
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0x001000 1024x768@60Hz (VESA)
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0x002000 1024x768@70Hz (VESA)
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0x004000 1024x768@75Hz (VESA)
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0x008000 1280x1024@75Hz (VESA)
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0x010000 - 0x800000 Manufacturer reserved
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Notes:
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- The eeprom.o module will also attach to a DDC monitor. Install the
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ddcmon.o module before the eeprom.o module to prevent this.
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Alternatively, give the eeprom.o module an ignore= parameter or
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a checksum= parameter. The ddcmon.o module will not attach to non-DDC
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eeproms because it checks for a DDC 'signature' at the beginning
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of the DDC Monitor's eeprom.
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- If a DDC monitor eeprom lacks the 'signature', you may use the
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'force' parameter (modprobe ddcmon force=x,0x50 where 'x' is the
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i2c bus number).
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- This module requires a bus driver for your video chip to access the
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DDC bus. In this package, drivers exist for Voodoo3/Banshee chips.
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See documentation for those drivers in ../busses. Other drivers
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(Matrox and NVidia, for example) are available in the kernel or
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elsewhere. See our 'Supported Devices' web page for details.
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- There is a checksum over the 128 bytes in the eeprom but the driver
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does not check it.
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- More information is available in the eeprom which could be made
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available by enhancing the driver.
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To see the entire eeprom, use the eeprom.o module instead of ddcmon.o.
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However, then you lose the DDC-specific formatting.
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- This driver does not support the DDC/CI (DDC2Bi) bidirectional
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communications channel to the monitor for controlling the monitor.
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- The driver caches the data from the monitor and only rereads it
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from the eeprom if the cache is more than 5 minutes old.
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- X 4.0 also accesses the DDC monitor EEPROM to auto-configure itself.
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There could possibly be conflicts from these multiple accesses.
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