How to fill out a Mode for a Panel Fitter

[Rian Quinn]

Working on getting cloning to work on a laptop, and realized that laptop
panel's only provides a single resolution. At least with Intel, these
usually have a panel fitter that allows you to set the CRTC to any
resolution, and the panel fitter scales for you.

We also figured out that you can use DRM_MODE_SCALE_FULLSCREEN
with drmModeConnectorSetProperty and the "scaling mode" property to tell
the panel fitter how you want it to scale.

The problem that I have is, how exactly should we fill in the modeInfo
structure. Right now, we have gotten it to work on all of our test
equipment (two laptops) by just taking the preferred mode, and changing
it's vdisplay and hdisplay to the resolution that we want. The rest of the
settings are left unchanged, which in my mind makes no sense.

One option that I was thinking of was to take the mode from the other
monitor that is not being scaled. Most of the settings in the modeInfo
struct should be good, except I noticed in testing that the flags field is
different between the panel and a VGA monitor (and I really have no idea
what the flags field should be set to).

I also noticed that there is a DRM_MODE_TYPE_USERDEF type, and it would
make sense to me that the type should be changed to this since I am
defining it in software, but I'm not sure if it is actually used.

At any rate, do any of you have any insight on the proper way to fill out
this modeInfo struct when using the panel fitter and a user defined mode?

Thanks a ton,
- Rian
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