DisplayLink USB Devices on Linux Kernel 3.4.0

Linux kernel 3.4.0 is the first to include a new driver for DisplayLink-based USB 2.0 devices, called “udl”. udl is a port of the udlfb driver to Linux’s DRM architecture. David Airlie is doing this work, and the potential is very exciting. Eventually, this architecture will lead to a host of advantages, including GPU-accelerated 3D rendering to USB graphics adapters.

Both the new “udl”, and older “udlfb” framebuffer driver that we maintain are present in 3.4.0. Unfortunately, the new udl DRM driver is still maturing, and can cause kernel panics. With USB graphics devices present, you can determine which driver (“udlfb” or “udl”) is getting loaded with lsmod:

lsmod | grep "udl"

This change has a particular impact with Fedora 17 — the first open source distro to have automatic USB multiseat support — which shipped with Linux kernel 3.3.

Post-ship, Fedora 17 now offers a software update to kernel 3.4.0, which unfortunately causes problems: udl may be loaded for DisplayLink-based devices, and kernel panics are common and terminals often won’t come up. To the user, it appears to break multiseat.

So to fix the issues you’ll see with 3.4.0, we recommend disabling udl for the time being. The stable udlfb driver is still present in the kernel, and will get matched against your hardware automatically once udl is no longer loaded. The easiest way to do this is to run the following commands and reboot:

echo "blacklist udl" | sudo tee --append /etc/modprobe.d/udlfb.conf
sudo depmod -a
sudo dracut -f /boot/initramfs-$(uname -r).img $(uname -r)

One the server reboots, udlfb should match all USB graphics devices and be fully stable. Please let us know if you have any trouble. And in coming Linux kernel versions, udl will continue to improve and at some point udlfb will be able to be retired in favor of it.

Plugable DC-125 USB 2.0 Multiseat Zero Client for Windows Multipoint Server and Fedora Linux (VGA up to 1440x900 / 1... Product Details $64.95

Plugable’s 7 Port USB Hub Gets Upgrades

We’re happy to announce the the Plugable USB2-HUB-AG7 seven-port hub with three-amp power supply is back in stock. One of Plugable’s goals is to continuously improve our products based on customer feedback. Manufacturing took a little extra time with this batch to implement some important changes.

Tighter Fit
The biggest change we made was to make sure the hub’s power cord stays snug in the hub.

That might not seem like much of a big deal, but the looseness of the of the power supply’s barrel connector was the No. 1 complaint we received from customers about older models of the seven-port hub.

We also tightened the fit of the mini-USB port where you insert the data cable that connects the hub to a computer.

Go Longer
The data cable now spans 56 inches, about a foot longer than before as a result of customer requests, providing increased flexibility and distance in positioning the hub away from the host computer.

When Less is More
Improvements aside, some customers ask why Plugable offers a self-powered seven-port hub when we already sell a self-powered 10-port hub. While the two hubs do the same thing–connect a bunch of USB devices to a computer–each offers different benefits.

The seven-port hub is better for devices that need a lot of power through the USB connection. The seven-port has a larger power supply than the 10-port hub: 3 amps versus 2.5 amps. You’ll find few other USB 2.0 hubs with this much total amperage.

Power Per Port
If you had multiple devices that all wanted to draw the USB 2.0 maximum amperage of 500 milliamps available when attached to a hub that is connected to a computer, you could attach about six of these devices to the seven-port hub (6  x 500mA = 3A) and only five to the 10-port hub (5 x 500mA = 2.5A). And in this scenario you would have gotten value out of six of ports on the seven-port hub but only half of the ports on the 10-port hub. Note that just because the hub provides this much power, doesn’t mean that devices will charge without a computer attached. That behavior is outside of the USB spec, and is determined by the particular device. Apple devices, in particular, require tricks to charge with any hub.

Per-Port LEDs
We think of the 7-port hub as our “power user” hub both because of the higher average power per port, and because of other features like the nice per-port LEDs on the 7-port hub that allow you to quickly see which ports have successfully configured on the host.

Works with Everything
The hub works with any USB 2.0 capable host: Windows, Mac, Linux, XBOX, Wii, Tivo, etc — anything with a USB port and support for hubs. The hub’s controller delivers the best performance and compatibility of any USB 2.0 hub controller out there.

Whatever your needs, we always aim to support you as best we can. If you have questions about either the improved Plugabale USB2-AG7 seven-port hub or any of our products, feel free to write us below or via e-mail to support@plugable.com. We’re here to help.

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Switcheroo! Cool Uses of a USB Switch

The best thing about interacting with customers–beyond the joy that comes from helping people solve problems–is learning the ways they’re using our products, especially when they come up with purposes beyond any we ever envisioned. Here are two examples of novel uses of the Plugable USB2-SWITCH2 USB 2.0 switch for one-button swapping of a USB device or hub.

Computer A Might Not Be A Computer
You might notice in the introduction that the USB2-SWITCH2′s title was shortened from its full name of “USB 2.0 switch for one-button swapping of a USB device or hub between two computers.” And that’s where the first story begins.

A customer wrote us with the following situation. He had a Cannon printer/scanner/copier that he had WiFi-enabled by connecting it to his Apple AirPort Extreme base station via a USB cable. Now he could print to the Cannon device from any computer on his WiFi network.

But if he wanted to scan with the Cannon, he needed to establish a direct USB connection between the Cannon and a computer. This meant unplugging the Cannon from the AirPort base station and connecting it to a computer–a cumbersome, inefficient process.

His solution:

  • Connect the Cannon printer/scanner/copier to the switch’s USB output port.
  • Connect the AirPort Extreme to USB input port A on the switch.
  • Connect a computer to USB input port B on the switch.
Diagram of an Apple AirPort Extreme and a PC sharing access to a printer/scanner via a Plugable USB2-SWITCH2.

Now when he needed to print, he could make sure that the switch gave the AirPort control over the USB connection to the Cannon. Any computer or tablet on the WiFi network capable of printing to the Cannon could send data there via the AirPort.

But when he needed to scan something, he could swap access to the computer plugged into the switch’s input port B to establish the necessary direct USB connection between that computer and the Cannon device. He didn’t even need to leave a computer permanently attached to port B. He could just leave the USB cable in port B and attach it to a computer as needed.

When we first released the switch, we wrote a blog post about how you could attach a hub to the switch’s output port and then provide access between two computers to multiple USB devices. We never considered that one of the devices on the input ports could be something like an AirPort that allowed multicomputer access to whatever device or hub was attached to the switch.

We salute the ingenuity of our engineering-focused customer who opened our eyes to this possibility and thank him for sharing his story.

Turning Off the USB Connection
Our second switch-master had a Bose speaker system that could be used with multiple types of playback devices.

His PC needed to connect to the Bose speakers via a USB cable.

A non-USB device could be connected to the speakers from its heaphone jack to a 3.5 millimeter input jack in the speakers via a male-to-male stereo cable.

The problem was that when the PC was plugged in to the speakers via USB, the customer had to unplug the stereo cable . The customer wanted to end this annoyance of continually fiddling with which cable was connected.  Plus, if you’ve ever had a cable that you use with a particular device, you  know how easy it is to lose that cable if you can’t just leave it attached where you use it.

It might seem odd that the USB2-SWITCH2 could have any benefit in this scenario. But here’s what our customer did.

  • Connect the Bose speakers into the switch’s output port.
  • Connect his computer into USB input port A on the switch.
  • Connect nothing into USB input port B on the switch.
Diagram of using the Plugable USB2-SWITCH2 to connect just one USB device to a speaker system

Now he could leave the USB and stereo cables connected plugged in simultaneously.

To play sound from his PC, all he had to do was use the computer on input port A. To playback sound over the stereo cable, he could swap the switch to input port B. With no device attached to input B, the Bose speakers acted as if there was no USB cable plugged in at all.  Therefore, the speakers played back the sound being transmitted through the stereo cable instead.

This customer transformed our switch for device sharing into an on-off switch for the Bose’s USB connection simply by recognizing that sometimes nothing is the best thing to plug into the switch’s port B.  Well done, sir.<

What’s Your Story?
The switch is one of the simplest devices Plugable manufactures, so to know that our customers are finding complicated new uses for it makes us wonder what’s being done with some of our more complex offerings. Feel free to share your usage stories below. We love to hear from you, and you might inspire the next great new idea for getting the most out of Plugable products.

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