I have a Radeon HD5450 using open-source radeon driver. I have two monitors connected, one to DVI port and the other to VGA port.

Xorg.0.log gets them correctly as:

[    21.515] (II) RADEON(0): EDID for output DVI-0
[    21.515] (II) RADEON(0): Manufacturer: ADI  Model: 217a  Serial#: 14703
[...]
[    21.549] (II) RADEON(0): EDID for output VGA-0
[    21.549] (II) RADEON(0): Manufacturer: CRN  Model: 10  Serial#: 40

However, xfce4-display-settings list:

- Digital display
- ADI 17"

It looks like some kind of off-by-one error reading EDID. I would expect the list to contain something like:

- ADI 17" (on digital port)
- CRN 20" (on analog port)