Beacause I don’t have a HDMI display~
If I remember correctly, the resolution was not great, but it had worked. This was, almost a year back. Now I use HDMI-to-HDMI with my new monitor.
Technically the only way VGA will succeed is one of the following:
- The default resolution for the driver happens to work for your VGA device.
- There is an acceptable mode which you’ve hacked in the kernel to be the default mode, and the VGA monitor “gets lucky” and uses that mode. You won’t be creating new modes by doing this, you’ll only change the fallback mode for when EDID is not present (the EDID is how auto configuration works, and the driver only accepts EDID for configuration).
- You have an “active” adapter which you’ve programmed the correct EDID data into it so you can fake being a true HDMI monitor.
I tried to use an active HDMI to VGA adapter that works successfully with my PC, but I didn’t get the image, it seemed to me that it didn’t work at all.
This may work with another adapter or if you make changes to the software.
For the active adapter, you’d want to see if the EDID made it through:
sudo -s cat `find /sys -name 'edid'` exit
…then go to http://www.edidreader.com, and verify the checksum is valid (you’d paste in the hex data).
If no EDID data is present, then the adapter failed. If EDID is present, but the checksum is not valid, then the adapter has an invalid EDID installed. If data is both present and valid, then the additional logging provided by
ModeDebug in the “
/etc/X11/xorg.conf” would allow the driver to describe exactly what it thinks of each mode from the EDID, and whether it accepts or rejects. The edit would be to add an option to section “Device”:
Section "Device" ... Option "ModeDebug" ... EndSection
Once extra logging is in place the correct “
/var/log/Xorg.0.log” (or sometimes
.1.) will tell us everything we need to know about the modes (though it would require you to try the active VGA-to-HDMI adapter again).
thanks for everyone