Chances are, you or someone you know has had to deal with plug-and-play (PnP) hardware. These devices are just like “legacy” devices, except they have no jumpers to configure the resources (i.e., IRQs, DMAs and I/O addresses). PnP cards expect the computer, either the BIOS or the operating system, to find and configure the card. It's an excellent idea, but why?
Most Linux users enjoy configuring their computers—getting their hands dirty working with the hardware. On the other side of the coin is the user who expects his computer to turn on in the morning and be ready for him to complete his work without intervention by him. This type of user will also add hardware to his computer, but does not want to spend time finding free resources and setting them. PnP hardware is ideal for him.
This user can purchase a plug-and-play device, put it in his computer, and the configuration is done automatically. This idea of automatic configuration was designed into the PCI bus, the newer of the common busses. Unfortunately, most users still rely on the standard architecture defined by the industry; that is, the ISA bus. It works well, but still has its limitations. Most notably, plug-and-play was not considered when ISA was designed.
The designers of the plug-and-play standard decided to extend plug-and-play to ISA devices. Wouldn't it be nice to have some sort of detection and configuration scheme to find these devices and set them up for the user? Think how easy computers would be! So, the designers set up a scheme to find ISA cards and configure them to the jumpered resources on the card. Hardware vendors loved the idea and decided to cooperate by suggesting the removal of all the jumpers.
Now we have a fully functional plug-and-play system for the ISA bus, right? Well, not exactly. It still has a way to go before it is all the way out the door. PCI architecture will take over in the next few years before plug-and-play ISA works without any problems. For now, we have to work with these plug-and-play ISA devices while mourning the loss of our beloved jumpers.
PnP ISA devices can be used in several ways under Linux. The kernel can find and configure them before loading any other drivers. This method sometimes fails to find all devices and to initialize the devices. It also requires patching the kernel with one of the PnP add-ons.
Another way, which I recommend, is to use an initialization program at the user level. You create a configuration file with your devices and specify the resources each device is to use. Then, this file is read by an initialization utility that configures the devices. However, this method does require the drivers for these devices to be compiled as kernel modules.
I have tried a couple of these user-level configuration programs, and the one I have found to be the easiest and most reliable is the isapnptools package. This program is designed to work on systems with or without a PnP-compatible BIOS. It will not interfere with “legacy” ISA devices either (devices with jumpers); at least, I have not had that problem.
As an example, I will configure a PnP sound card and load the driver for it. I will assume you can install the card and you have a working knowledge of Linux. Here's a basic overview of the setup process:
getting the isapnptools package
dumping all possible values
choosing your resources
testing the configuration
compiling the kernel driver
enabling the device at bootup
Most of the latest Linux distributions come with the isapnptools package. However, you may want to grab the latest version from the isapnptools web page, http://www.roestock.demon.co.uk/isapnptools/. At the time of this writing, the latest version is 1.17.
After downloading the file, extract the contents and compile it. Some systems may require editing the Makefile. Check the included INSTALL file for more information. As root, I used the following commands to compile and install the package:
tar xvzf isapnptools-1.17.tar.gz cd isapnptools-1.17 make make install (as root)
The installation will create the isapnp and pnpdump programs along with their accompanying man pages and sample configuration file.
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- Designing with Linux
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- Red Hat Enterprise Linux 7.1 beta available on IBM Power Platform
- January 2015 Issue of Linux Journal: Security
- Slow System? iotop Is Your Friend
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