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* patched drm_edid.c
* patched drm_edid.c
== Links ==
* http://www.nathandumont.com/node/241

Version vom 27. Februar 2013, 14:38 Uhr

VGA

Video Graphics Adapter

pinouts

VGA pinouts

edid

EDID I used EDID 1.3
Windows

  • it accepts:
    • standart timings
    • established timings
  • it looks like Windows XP doesn't like "prefered timings"

Linux

  • The kernel module drm handels all the display stuff
  • it accepts:
    • established timings
    • standart timings
    • prefered timings

build a fake monitor

  • Terminate the color lines with 75ohms
  • Attach a 24C02 serial eeprom to the specified pins (24c04 - 24c16 is possible to )

flash a new edid

  • Load the kernelmodule i2c-dev
  • Get i2c-tools
  • build the i2c-tools
  • Become root: Sudo -s
  • Add the tools folder to the PATH: PATH=$PATH:< ... >/i2c-tools/tools
  • Run i2cdump to find the correct BUSID (device at 0x50 and 0x51)
  • Flash new EDID with write-edid.sh
  • Note the input file is plain/text with hexvalues, spaces and newlines only

create custom edid

Note

  • the tool outputs .dat-files, that need to be editet by hand, it contains invalid symbols
  • you can use the export function to generate .raw files and use hexdump to convert them to plain/text hex

hack the kernel module drm

  • install linux-source
  • install linux-kernel-headers
  • modify the Makefile
all:
	$(MAKE) -C $(KDIR) M=$(PWD) modules
	cp drm.ko /lib/modules/`uname -r`/kernel/drivers/gpu/drm
	cp drm_kms_helper.ko /lib/modules/`uname -r`/kernel/drivers/gpu/drm
	chmod 755 /lib/modules/`uname -r`/kernel/drivers/gpu/drm
	update-initramfs -u
  • patch drm_edid.c , it doesn't accept vsync_width OR hsync_width to be 0

Results

Mesa 9.0

Label EDID Value Description
AMD RV710 Vsync = 0 no graphics
AMD RV710 Vsync = 1 random graphics
AMD RV710 Htotal = Hactive no graphics
AMD RV710 Hsync = 0 normal graphics*
AMD RV710 Vtotal = Vactive + 2 random graphics
  • patched drm_edid.c

Links