Книга: Embedded Linux Primer: A Practical, Real-World Approach

8.2.4. modprobe

8.2.4. modprobe

This is where the cleverness of modprobe comes into play. In Listing 8-7, we see the relationship between the ext3 and jbd modules. The ext3 module depends on the jbd module. The modprobe utility can discover this relationship and load the dependent modules in the proper order. The following command loads both the jbd.ko and ext3.ko driver modules:

$ modprobe ext3

The modprobe utility has several command line options that control its behavior. As we saw earlier, modprobe can be used to remove modules, including the modules upon which a given module depends. Here is an example of module removal that removes both jbd.ko and ext3.ko :

$ modprobe -r ext3

The modprobe utility is driven by a configuration file called modprobe.conf. This enables a system developer to associate devices with device drivers. For a simple embedded system, modprobe.conf might be empty or might contain very few lines. The modprobe utility is compiled with a set of default rules that establish the defaults in the absence of a valid modprobe.conf. Invoking modprobe with only the -c option displays the set of default rules used by modprobe.

Listing 8-8 represents a typical modprobe.conf, which might be found on a system containing two Ethernet interfaces; one is a wireless adapter based on the Prism2 chipset, and the other is a typical PCI Ethernet card. This system also contains a sound subsystem based on an integrated Intel sound chipset.

Listing 8-8. Typical modprobe.conf File

$ cat /etc/modprobe.conf
alias eth1 orinoci_pci
options eth1 orinoco_debug=9
alias eth0 e100
alias snd-card-0 snd-intel8x0
options snd-card-0 index=0

When the kernel boots and discovers the wireless chipset, this configuration file instructs modprobe to load the orinoco_pci device driver, bound to kernel device eth1, and pass the optional module parameter orinoco_debug=9 to the device driver. The same action is taken upon discovery of the sound card hardware. Notice the optional parameters associated with the sound driver snd-intel8x0.

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