Trying to use Radeon driver on Apple eMac

Stan Cunningham stan.cunningham at
Tue Dec 16 15:55:10 PST 2008


--- On Tue, 12/16/08, Alex Deucher <alexdeucher at> wrote:
> > The EDID for the built-in monitor of all PowerPC Macs
> can be found under /proc/device-tree. Since it's hard
> for anyone but Apple to know about every single type of
> monitor they've put into their computers, wouldn't
> it be better for the radeon driver to find the EDID at
> runtime by looking in the OpenFirmware device tree rather
> than relying on a possibly inaccurate and out of date static
> quirk list?
> >
> > I think the xresprobe utility has a file called
> ddcprobe/of.c that does exactly that (ie. parses the
> OpenFirmware device tree and extracts the EDID). Why
> doesn't the radeon driver just use ddcprobe/of.c? This
> would seem the most robust way of getting EDID on all Apple
> PPC computers (iMac, Emac, Clamshell, Powerbook, PowerMac,
> etc).
> >
> >
> I didn't realize this existed.  Does the OF tree have
> hardcoded edids,
> or does it just read the edid from the device and store it
> in the
> tree?  if it just reads from the device (which I suspect it
> does),
> then it's doing the same thing the driver is already
> doing.  Most
> built in apple screens (ibooks, powerbooks, imacs, etc.)
> have an edid,
> it's just the eMac that seems to not.

I'm not sure how OpenFirmware is implemented to know the EDID. On my iMac G3, the EDID is located at:

/proc/device-tree/pci at f0000000/ATY,Rage128P2ks at 10/EDID

Joseph, does your eMac have an EDID file in a similar location?

I agree with ajax that X should fall back to reading the EDID from the firmware (OpenFirmware or ACPI) if DDC doesn't work. And since reading from the firmware doesn't require's hardware drivers, this mechanism could be used as a fallback for _all_ drivers, not just radeon.

Apple seems to have placed information about their built-in displays (including a bunch of EDIDs) in a package called AppleDisplays that comes with OpenDarwin (the latest version is AppleDisplays-160.0.9), which can be downloaded from .

For Apple computers in particular, a second fallback could be to use the information provided by the AppleDisplays package.



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