[Libdlo] EDID and dynamic modset issues

[Todd Grayson]

Bernie,

Thank-you for the quick response. 

Here is some additional information:

When connecting and disconnecting monitors while the Displaylink device is still connected the framebuffer size, refresh rate/timings, and resolution remain the same.

When disconnecting the Displaylink device then changing monitors and reconnecting the Displaylink device the resolution, framebuffer size, and refresh rate/timings change to match the monitor's preferred mode.

As a note, initially I was testing using a DVI to VGA adapter (supplied with the device) which seemed to cause the probe() function to obtain incorrect information about the monitor's preferred mode. When switching to use the default DVI connection instead of the DVI to VGA adapter probe() correctly obtained the monitor's preferred mode and set everything correctly.

What we are trying to do is to be able to force the desired resolution and refresh rate using fbset in those instances where probe() does not obtain the correct information (in many cases our monitors only have VGA connections) or in cases where we require different supported resolutions. (ie. when using a CRT monitor).

Todd

________________________________
From: Bernie Thompson <bernie at berniethompson.com>
To: Todd Grayson <toddgrayson at yahoo.com>
Cc: libdlo at lists.freedesktop.org
Sent: Tue, January 19, 2010 9:18:54 AM
Subject: Re: [Libdlo] EDID and dynamic modset issues

Hi Todd,

Thanks for the good description.  Yep, the current code has a limitation of only allocating the virtual framebuffer at one point - in probe() - based on the EDID at that time.  The workaround from an end-user perspective is if you need to switch monitors, also unplug/plug the DisplayLink device.

Just to understand priorities -- what's the scenario where you're connecting and disconnecting monitors (while keeping the DisplayLink device connected)?

Thanks,
Bernie


On Tue, Jan 19, 2010 at 7:11 AM, Todd Grayson <toddgrayson at yahoo.com> wrote:

>When using the latest git.plugable.com master branch as well as the displaylinkfb module I am getting issues with the framebuffer device size not being large enough to set different modes even though they are supported by the monitor.
>
>>My understanding is that udlfb uses EDID to find the monitor's preferred mode. As a result it looks like when creating the framebuffer initially it is setting the memory size based on the returned resolution not allowing any resolution larger than that returned resolution.
>
>>When trying to set the framebuffer size to a larger resolution than the one initially created using the fbset utility there is a returned error of:
>
>>ioctl FBIOPUT_VSCREENINFO: Invalid argument
>
>>Setting the resolution to a smaller size works fine.
>
>>Any help would be appreciated.
>
>
>
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-- 
Bernie Thompson
Plugable Technologies
Bellevue, WA USA
http://plugable.com/
+1 425 533 5219
skype: bernie.thompson



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