3.3.1. Ethernet Autoprobing
Many of the Linux Ethernet drivers are smart enough to know how to search for the location of your Ethernet card. This saves you having to tell the kernel where it is manually. The Ethernet HOWTO lists whether a particular driver uses autoprobing and in which order it searches the I/O address for the card.
There are three limitations to the autoprobing code. First, it may not recognize all cards properly. This is especially true for some of the cheaper clones of common cards. Second, the kernel won't autoprobe for more than one card unless specifically instructed. This was a conscious design decision, as it is assumed you will want to have control over which card is assigned to which interface. The best way to do this reliably is to manually configure the Ethernet cards in your machine. Third, the driver may not probe at the address that your card is configured for. Generally speaking, the drivers will autoprobe at the addresses that the particular device is capable of being configured for, but sometimes certain addresses are ignored to avoid hardware conflicts with other types of cards that commonly use that same address.
PCI network cards should be reliably detected. But if you are using more than one card, or if the autoprobe should fail to detect your card, you have a way to explicitly tell the kernel about the card's base address and name.
At boot time you can supply arguments and information to the kernel that any of the kernel components may read. This mechanism allows you to pass information to the kernel that Ethernet drivers can use to locate your Ethernet hardware without making the driver probe.
If you use lilo to boot your system, you can pass parameters to the kernel by specifying them through the append option in the lilo.conf file. To inform the kernel about an Ethernet device, you can pass the following parameters:
ether=irq,base_addr,[param1,][param2,]name
The first four parameters are numeric, while the last is the device name. The irq , base_addr , and name parameters are required, but the two param parameters are optional. Any of the numeric values may be set to zero, which causes the kernel to determine the value by probing.
The first parameter sets the IRQ assigned to the device. By default, the kernel will try to autodetect the device's IRQ channel. The 3c503 driver, for example, has a special feature that selects a free IRQ from the list 5, 9, 3, 4 and configures the card to use this line. The base_addr parameter gives the I/O base address of the card; a value of zero tells the kernel to probe the addresses listed above.
Different drivers use the next two parameters differently. For shared-memory cards, such as the WD80x3, they specify starting and ending addresses of the shared memory area. Other cards commonly use param1 to set the level at which debugging information is displayed. Values of 1 through 7 denote increasing levels of verbosity, while 8 turns them off altogether; 0 denotes the default. The 3c503 driver uses param2 to choose between the internal transceiver (default) or an external transceiver (a value of 1). The former uses the card's BNC connector; the latter uses its AUI port. The param arguments need not be included at all if you don't have anything special to configure.
The first non-numeric argument is interpreted by the kernel as the device name. You must specify a device name for each Ethernet card you describe.
If you have two Ethernet cards, you can have Linux autodetect one card and pass the second card's parameters with lilo , but you'll probably want to manually configure both cards. If you decide to have the kernel probe for one and manually configure the second, you must make sure the kernel doesn't accidentally find the second card first, or else the other one won't be registered at all. You do this by passing lilo a reserve option, which explicitly tells the kernel to avoid probing the I/O space taken up by the second card. For instance, to make Linux install a second Ethernet card at 0x300 as
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