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This file describes which modules can be automatically loaded at boot time
with Hotplug and what to do with the ones which cannot be loaded by Hotplug.
The following classes of modules will be loaded automatically by the 2.6
kernel itself or the hotplug initscript:
* The modules that directly correspond to some ISAPNP, PCI or USB hardware
will be loaded by hotplug initscript. Such modules are called "detectable"
below. To verify if the module is detectable, check for the presence of the
MODULE_DEVICE_TABLE macro in its source code. If you don't have enough skills
to do that, there is another way. Compile and install the modules. Find the
compiled module in the /lib/modules/`uname -r` directory.
Execute the following command:
modinfo /path/to/this/module.ko
If you see an alias that begins with "pci:" or "usb:", then the module
is detectable. For example, the snd-fm801.ko module is detectable because it
has a "pci:v00001319d00000801sv*sd*bc04sc01i*" alias.
* The modules that are listed in the modinfo output as dependencies of
detectable modules will be loaded automatically by hotplug scripts. For
example, the detectable snd-fm801.ko module depends upon snd-pcm,
snd-opl3-lib, snd-mpu401-uart, snd and snd-tea575x-tuner modules. They will
be loaded automatically by Hotplug if a ForteMedia-based soundcard is
present in the system.
* Filesystem modules (e.g., vfat.ko), NLS character sets (e.g., nls-koi8-r.ko)
and most network protocol drivers (e.g., ipv6.ko) are loaded automatically
by the kernel upon the first need.
* Character and block device drivers are loaded automatically even without the
Hotplug package installed when an application opens the existing device node
without a loaded driver. This is controlled by the aliases in
/lib/modules/`uname -r`/modules.alias (generated automatically) and
/etc/modprobe.conf (created manually) files that begin with char-major and
block-major. However, this relies upon the device node being already present
even when the module is not loaded, and this is not the case with Udev. For
example, the following modules can be loaded automatically on first demand
when Udev is not used: lp, ppp-generic. They will not be loaded
automatically when Udev is used.
* Devfsd also can load modules on demand. However, since devfs is deprecated,
this is not covered here.
* Almost everything else is not loaded automatically. For example, the
following modules will not be loaded automatically: ide-cd, snd-pcm-oss
There are several solutions for using such undetectable drivers:
* Compile them directly into the kernel, not as modules. If you seem to be
unable to do this, it's because you selected some dependency of such a
driver as a module.
* Use a distribution-provided script to load these modules at boot time
unconditionally. On Debian systems, it's sufficient to put their names in
the /etc/modules file.
* Add a line to the /etc/modprobe.conf file that tells module-init-tools about
a "missed dependency" between modules, e.g.:
install snd-pcm modprobe -i snd-pcm ; modprobe snd-pcm-oss ; true
This way, the OSS compatibility module will be loaded automatically for
all PCI soundcards supported by ALSA. Note, however, that this solution
depends upon snd-pcm.ko being a module. More examples of such
"dependencies" are shown below:
install snd-seq modprobe -i snd-seq ; modprobe snd-seq-oss ; true
install parport modprobe -i parport ; modprobe lp ; modprobe ppdev ; true
install mptbase modprobe -i mptbase ; modprobe mptscsih ; modprobe mptctl ; modprobe mptlan ; true
install usb-storage modprobe -i usb-storage ; modprobe sd-mod ; true
As you can see, some detectable module or its dependency is put on the
left, and its undetectable helpers are enumerated then. Note however that
this approach doesn't help you to load modules like nbd.ko that don't depend
upon any hardware at all.
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