[PATCH 2/2] drm/radeon/kms: enable underscan option for digital connectors

Alex Deucher alexdeucher at gmail.com
Wed Aug 4 07:35:34 PDT 2010

2010/8/4 Marius Gröger <marius.groeger at googlemail.com>:
> Am 04.08.2010 01:59, schrieb Alex Deucher:
>> This connector attribute allows you to enable or disable underscan
>> on a digital output to compensate for panels that automatically
>> overscan (e.g., many HDMI TVs).  Valid values for the attribute are:
>> off - forces underscan off
>> on - forces underscan on
>> auto - enables underscan if an HDMI TV is connected, off otherwise
>> default value is auto.
> Terrific! Two questions:
> - inevitably, on my TV Set (SONY KDL 3000) this now doing too much
> underscan. In pixels: without your patch, I used a custom modeline to
> map 1280x720p to 1220x680p, so I'm 40 pixels down in each dimension. How to
> fix that?

Adjust radeon_crtc->v_border and radeon_crtc->h_border in the patch to
whatever size you want.

> - more of a general drm question I guess: in what way are the connector
> attributes available on the command line? I couldn't find a complete
> kernel command line or modprobe invocation.

I guess you'll need to write an app to invoke the proper ioctls to
change them at runtime.  I'm not sure if one exists or not at the


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