Linux Support For Higher-Res Monitors on Lower-Res DisplayLink Devices
Posted on 21. May, 2010 by Bernie Thompson in UGA-2K-A
On Windows and Mac, if you plug in a monitor with a higher resolution than your adapter supports, the driver will automatically fall back to the best common mode between the two.
Linux hasn’t had that support — it would try to set the highest mode the monitor is capable of, often resulting in a black screen. Especially common for the DL-125 chip, with its mode limits of 1440×900/1280×1024.
That’s a shame because the DL-125 chip is a smart choice in many cases – by limiting itself to those lower modes, it stays more consistently within the limits of the USB 2.0 bus, resulting in more consistent performance.
So coinciding with the launch of Plugable’s DisplayLink DL-125 based products (UGA-125 and UGA-125-HUB), changes have been implemented to bring Linux roughly up to the level of Windows and Mac in this area for DisplayLink devices. This also helps devices like the UD-160-A when running on monitors greater than its limit of 1920×1080.
The kernel framebuffer driver udlfb has been enhanced to read the resolution limit from the firmware descriptors of the device, and adhere to it.
On the X server side, we needed a driver which would limit itself to the resulting reduced mode list. Unfortunately, the existing displaylink X server reads EDID directly, and assumes the adapter can do whatever the monitor can do.
We’ve been wanting to get rid of the need for a displaylink-specific X server, and the standard xf86-video-fbdev driver runs with the best existing mode, rather than trying to set a higher one in EDID. So this was a good trigger for converting over.
So xf86-video-fbdev has been enhanced with X Damage protocol support, ported from Roberto’s displaylink driver. This is still a little in-flux from an interface perspective, but from a functional perspective it’s done and fully performant.
So it’s now possible to run with a modified generic fbdev driver, which talks to udlfb, with full performance and without needing defio (although there’s also some good news in the defio space, which will be posted about later).
You can grab the latest udlfb kernel module with a “git clone http://git.plugable.com/webdav/udlfb”. Compile with “make && sudo make install && sudo depmod -a”
And you can grab the latest modified xf86-video-fbdev with a “git clone http://git.plugable.com/webdav/xf86-video-fbdev”. Compile with “./autogen.sh && make && sudo make install”
You’ll need a very recent xorg-macros version (1.4), which in package “sudo apt-get install xutils-dev”
To use the new X server, you must turn on the new “ReportDamage” option to fbdev. Modify your existing xorg conf like this:
Section "Device" Identifier "dl" Driver "fbdev" Option "ReportDamage" "true" Option "fbdev" "/dev/fb0" EndSection
And you should be all set to go. This new X server should work with the existing udlfb in the staging tree of kernel 2.6.31+ for now, as it’s re-using the same original ioctl. But may require modeset changes that are only in 2.6.34+.
Coverage of UGA-125 family launch
Posted on 03. May, 2010 by Bernie Thompson in Windows
We’re excited to be launching the new UGA-125 and UGA-125-HUB products, available on Amazon now. Check out the following for sampling of 3rd party coverage so far:
A discount code for launch: the UGA-125
Posted on 27. Apr, 2010 by Bernie Thompson in Windows
We’re about to formally launch Plugable’s new UGA-125 USB 2.0 to VGA/DVI/HDMI Adapter for Multiple Monitors up to 1440×900 each
We’ve been able to get the UGA-125 down under the $50 price point with all the great service and free shipping benefits of Amazon.com. But for our fans who follow Plugable, we have an additional discount.
Enter claim code “LOVEPLUG” before checkout, and you’ll get an additional $5 off. But only during our launch window, from now until the end of April. And only selling in the USA for now, sorry.
And whether in the market for a new product or not, we’d like to send a big “thank you!” to all our loyal customers who take the time to follow what’s new at Plugable.
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