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How to disable underscan when using kms?

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  • How to disable underscan when using kms?

    Since I upgraded to 2.6.36 it defaults to underscan on my tv on hdmi.

    I googled and found that it is now default. How do I tell the radeonmodule not to underscan? I guess I have to use the connector_table option but I have no idea how to use it

  • #2
    xrandr --output <output> --set underscan off

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    • #3
      thanks

      great work with the open driver by the way.

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      • #4
        how about at boot time/console without X11

        the xrandr works fine, but requires one to enter X11...

        is there any way to disable it at boot time? i tried to list radeon module parameters with modinfo, but i saw no option to disable it...

        how about a console app for it or, even better, a kernel option to set the default value?

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        • #5
          Ideally, we expose all connector attributes via sysfs, but no one has had the time yet.

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          • #6
            stupid thing to have on by deafult suddenly.. and should atleast be possible to disable in xorg.conf

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            • #7
              Alex:

              This underscan in 2.6.36 is extremely annoying. What proportion of TV's these days even need underscan to begin with? I think that most (if not all) lcd/led and probably also plasma displays can be set to display native resolutions. Wouldn't underscan apply mainly to older things, like dlp and crt displays, with resolutions of UNDER 1080p? Certainly every TV I've seen supporting 1080p resolution has been able to display native output.

              Note that the underscan has some nasty effects beyond just black borders; a TV that has a visible area equal to its native resolution will end up with a scaled image when underscan is enabled, and that is real ugly.

              This really should default to underscan DISABLED unless explicitly ENABLED (i.e. kernel argument). Or at least there should be an option to disable underscan using a kernel argument since xrandr is a really hacky solution -- thing starts in underscan, plymouth loads underscan, x loads underscan, and then you either have to manually run xrandr or something does it automatically....

              I presume that replacing all instances of "UNDERSCAN_AUTO" and "UNDERSCAN_ON" with "UNDERSCAN_OFF" in the radeon code would fix this, correct?

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              • #8
                Unfortunately, many LCD TVs simply assume that HDMI input is a TV signal and overscan by default. I know that our Samsung does this, and there is no way to turn it off, or to use the correct resolution.

                So it either overscans (and half of your subtitles are gone), or it underscans and you have black borders around. You can't win.

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                • #9
                  Originally posted by pingufunkybeat View Post
                  Unfortunately, many LCD TVs simply assume that HDMI input is a TV signal and overscan by default. I know that our Samsung does this, and there is no way to turn it off, or to use the correct resolution.

                  So it either overscans (and half of your subtitles are gone), or it underscans and you have black borders around. You can't win.
                  How old is your LCD TV? And are you 100% sure you dont have that setting? It sometimes can have very confusing names in the menu on the TV.

                  I also think that underscan should be disabled by default, its very annoying.

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                  • #10
                    Most TV's, if not all, underscan by default since cable and satellite assume overscan and there's often garbage on the edges of the blanking areas due to vbi data. On the good ones you can turn it off, but most average users don't even know what underscan is, and I before I added the feature I got tons of bugs along the lines of "radeon crops image" or "radeon chooses wrong mode", etc. Unfortunately, there is no way for the driver to know whether the TV is overscanning or not.

                    The problem with a module parameter is that it's global and would either apply to all digital outputs or you'd need to have some hacky way to tell it what connectors you wanted it to apply to. I'm sure there are users out there that would want it disabled on one connector, but enabled on another, etc. As I've mentioned before, the best solution would be to expose the drm connector properties (tv standard, underscan, scaling, etc.) generically through sysfs. It shouldn't be too hard a task we already have code to expose the connectors and dpms info via sysfs, it would just need to be extended. Unfortunately, I won't have time to tackle it for a while.

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