aty128fb and EDID

Magnus Damm damm at
Mon Feb 10 21:14:53 EST 2003

> > Steal the code from the radeon dirver in the kernel.  It finds and parses
> > the EDID block in OF for ppc linux systems for LCD.

Yes, thanks. That's the short-term solution.
The problem is that the radeon driver only parses the "detail timings".
I want to support all timings including "established timings" and
"detailed timings".
And then it gets more complex...

> I guess you actually meant:
> | Move the code out of the radeon driver and make it sufficiently generic so it
> | can be used by the aty128 and other drivers?

Yes. Here's my grand plan:

1. Rearrange modes from modedb.c/macmodes.c into separate files for:
   * Standard VGA modes
   * Tweaked VGA modes (modex)
   * VESA modes
   * Archtecture-specific modes
   (* A mode calculator)
   This includes adding add/remove functions to be able to insmod/rmmod
   modules runtime.

2. Add EDID parsing code.
   The code should be able to list "established timings" and "standard timings".
   Modes should be built from "detail timings".
   Getting the EDID structure could be done in several ways:
   * Through Open Firmware (mac and maybe others)
   * Through the BIOS
   * Via I2C bitbanging (requires special support by the fb-driver)

3. Add code that gets information from the EDID parser and looks through the
   modes available and then creates a list of supported modes.

4. Add architecture-specific code that looks up the model and then returns a
   list of supported modes. This should be used if the machine doesn't have EDID
   information. (See aty128db.c and machine_is_compatible()).

5. Add code that takes the modes from 3 or 4 above and throws it at the fb-driver
   that looks them through and marks the supported modes with what colour-
   depths that are supported.

6. Add a "mode" variable for each framebuffer.
   This should make it possible to switch between the following states:
   * Safe - only modes that are listed by the monitor are accepted.
   * Standard - old standard modes that might work
   * Expert - funky timings that might blow your monitor
   The "Safe" mode is default.
   I don't know yet how the "mode"-variable should be controlled. /proc?

7. Add support to(/from) vga=ask. The user should be able to switch between
   the modes listed in 6 above.

And then we have VDIF... Feedback is very welcome.

/ magnus

BTW: I found some EDID data here:

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