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It has been seen that for some network mac drivers (i.e. lan78xx) the related module for the phy is loaded dynamically depending on the current hardware. In this case, the associated phy is read using mdio bus and then the associated phy module is loaded during runtime (kernel function phy_request_driver_module). However, no software dependency is defined, so the user tools will no be able to get this dependency. For example, if dracut is used and the hardware is present, lan78xx will be included but no phy module will be added, and in the next restart the device will not work from boot because no related phy will be found during initramfs stage. In order to solve this, we could define a normal 'pre' software dependency in lan78xx module with all the possible phy modules (there may be some), but proceeding in that way, all the possible phy modules would be loaded while only one is necessary. The idea is to create a new type of dependency, that we are going to call 'weak' to be used only by the user tools that need to detect this situation. In that way, for example, dracut could check the 'weak' dependency of the modules involved in order to install these dependencies in initramfs too. That is, for the commented lan78xx module, defining the 'weak' dependency with the possible phy modules list, only the necessary phy would be loaded on demand keeping the same behavior, but all the possible phy modules would be available from initramfs. A new function 'kmod_module_get_weakdeps' in libkmod will be added for this to avoid breaking the API and maintain backward compatibility. This general procedure could be useful for other similar cases (not only for dynamic phy loading). Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com> Link: https://lore.kernel.org/r/20240327141116.97587-1-jtornosm@redhat.com
266 lines
12 KiB
XML
266 lines
12 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<refentry id="modprobe.d">
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<refentryinfo>
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<title>modprobe.d</title>
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<productname>kmod</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Jon</firstname>
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<surname>Masters</surname>
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<email>jcm@jonmasters.org</email>
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</author>
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<author>
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<contrib>Developer</contrib>
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<firstname>Robby</firstname>
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<surname>Workman</surname>
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<email>rworkman@slackware.com</email>
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</author>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lucas</firstname>
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<surname>De Marchi</surname>
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<email>lucas.de.marchi@gmail.com</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>modprobe.d</refentrytitle>
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<manvolnum>5</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>modprobe.d</refname>
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<refpurpose>Configuration directory for modprobe</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/lib/modprobe.d/*.conf</filename></para>
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<para><filename>@DISTCONFDIR@/modprobe.d/*.conf</filename></para>
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<para><filename>/usr/local/lib/modprobe.d/*.conf</filename></para>
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<para><filename>/run/modprobe.d/*.conf</filename></para>
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<para><filename>/etc/modprobe.d/*.conf</filename></para>
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</refsynopsisdiv>
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<refsect1><title>DESCRIPTION</title>
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<para>Because the <command>modprobe</command> command can add or
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remove more than one module, due to modules having dependencies,
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we need a method of specifying what options are to be used with
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those modules. All files underneath the
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<filename>/etc/modprobe.d</filename> directory which end with the
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<filename>.conf</filename> extension specify those options as
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required. They can also be used to create convenient aliases:
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alternate names for a module, or they can override the normal
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<command>modprobe</command> behavior altogether for those with
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special requirements (such as inserting more than one module).
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</para>
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<para>
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Note that module and alias names (like other module names) can
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have - or _ in them: both are interchangeable throughout all the
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module commands as underscore conversion happens automatically.
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</para>
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<para>
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The format of files under <filename>modprobe.d</filename> is
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simple: one command per line, with blank lines and lines starting
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with '#' ignored (useful for adding comments). A '\' at the end
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of a line causes it to continue on the next line, which makes the
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file a bit neater.
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</para>
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</refsect1>
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<refsect1><title>COMMANDS</title>
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<variablelist>
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<varlistentry>
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<term>alias <replaceable>wildcard</replaceable> <replaceable>modulename</replaceable>
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</term>
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<listitem>
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<para>
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This allows you to give alternate names for a module. For example:
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"alias my-mod really_long_modulename" means you can use "modprobe
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my-mod" instead of "modprobe really_long_modulename". You can also
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use shell-style wildcards, so "alias my-mod*
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really_long_modulename" means that "modprobe my-mod-something" has
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the same effect. You can't have aliases to other aliases (that way
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lies madness), but aliases can have options, which will be added to
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any other options.
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</para>
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<para>
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Note that modules can also contain their own aliases, which you can
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see using <command>modinfo</command>. These aliases are used as a
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last resort (ie. if there is no real module,
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<command>install</command>, <command>remove</command>, or
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<command>alias</command> command in the configuration).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>blacklist <replaceable>modulename</replaceable>
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</term>
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<listitem>
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<para>
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Modules can contain their own aliases: usually these are aliases
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describing the devices they support, such as "pci:123...". These
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"internal" aliases can be overridden by normal "alias" keywords,
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but there are cases where two or more modules both support the same
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devices, or a module invalidly claims to support a device that it
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does not: the <command>blacklist</command> keyword indicates that
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all of that particular module's internal aliases are to be ignored.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>install <replaceable>modulename</replaceable> <replaceable>command...</replaceable>
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</term>
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<listitem>
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<para>
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This command instructs <command>modprobe</command> to run your
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command instead of inserting the module in the kernel as normal.
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The command can be any shell command: this allows you to do any
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kind of complex processing you might wish. For example, if the
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module "fred" works better with the module "barney" already
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installed (but it doesn't depend on it, so
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<command>modprobe</command> won't automatically load it), you could
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say "install fred /sbin/modprobe barney; /sbin/modprobe
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--ignore-install fred", which would do what you wanted. Note the
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<option>--ignore-install</option>, which stops the second
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<command>modprobe</command> from running the same
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<command>install</command> command again. See also
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<command>remove</command> below. </para> <para>The long term
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future of this command as a solution to the problem of providing
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additional module dependencies is not assured and it is intended to
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replace this command with a warning about its eventual removal or
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deprecation at some point in a future release. Its use complicates
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the automated determination of module dependencies by distribution
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utilities, such as mkinitrd (because these now need to somehow
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interpret what the <command>install</command> commands might be
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doing. In a perfect world, modules would provide all dependency
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information without the use of this command and work is underway to
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implement soft dependency support within the Linux kernel. </para>
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<para> If you use the string "$CMDLINE_OPTS" in the command, it will
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be replaced by any options specified on the modprobe command line.
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This can be useful because users expect "modprobe fred opt=1" to
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pass the "opt=1" arg to the module, even if there's an install
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command in the configuration file. So our above example becomes
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"install fred /sbin/modprobe barney; /sbin/modprobe
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--ignore-install fred $CMDLINE_OPTS"
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>options <replaceable>modulename</replaceable> <replaceable>option...</replaceable>
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</term>
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<listitem>
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<para>
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This command allows you to add options to the module
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<replaceable>modulename</replaceable> (which might be an
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alias) every time it is inserted into the kernel: whether
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directly (using <command>modprobe </command>
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<replaceable>modulename</replaceable>) or because the
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module being inserted depends on this module.
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</para>
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<para>
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All options are added together: they can come from an
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<command>option</command> for the module itself, for an
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alias, and on the command line.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>remove <replaceable>modulename</replaceable> <replaceable>command...</replaceable>
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</term>
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<listitem>
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<para>
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This is similar to the <command>install</command> command
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above, except it is invoked when "modprobe -r" is run.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>softdep <replaceable>modulename</replaceable> pre: <replaceable>modules...</replaceable> post: <replaceable>modules...</replaceable>
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</term>
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<listitem>
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<para>
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The <command>softdep</command> command allows you to specify soft,
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or optional, module dependencies. <replaceable>modulename</replaceable>
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can be used without these optional modules installed, but usually with
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some features missing. For example, a driver for a storage HBA might
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require another module be loaded in order to use management features.
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</para>
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<para>
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pre-deps and post-deps modules are lists of names and/or aliases of other
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modules that modprobe will attempt to install (or remove) in order
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before and after the main module given in the
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<replaceable>modulename</replaceable> argument.
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</para>
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<para>
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Example: Assume "softdep c pre: a b post: d e" is provided in the
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configuration. Running "modprobe c" is now equivalent to
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"modprobe a b c d e" without the softdep.
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Flags such as --use-blacklist are applied to all the specified
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modules, while module parameters only apply to module c.
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</para>
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<para>
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Note: if there are <command>install</command> or
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<command>remove</command> commands with the same
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<replaceable>modulename</replaceable> argument,
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<command>softdep</command> takes precedence.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>weakdep <replaceable>modulename</replaceable> <replaceable>modules...</replaceable>
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</term>
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<listitem>
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<para>
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The <command>weakdep</command> command allows you to specify weak module
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dependencies. Those are similar to pre softdep, with the
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difference that userspace doesn't attempt to load that
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dependency before the specified module. Instead the kernel
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may request one or multiple of them during module probe,
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depending on the hardware it's binding to. The purpose of
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weak module is to allow a driver to specify that a certain
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dependency may be needed, so it should be present in the
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filesystem (e.g. in initramfs) when that module is probed.
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</para>
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<para>
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Example: Assume "weakdep c a b". A program creating an
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initramfs knows it should add a, b, and c to the filesystem
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since a and b may be required/desired at runtime. When c is
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loaded and is being probed, it may issue calls to
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request_module() causing a or b to also be loaded.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1><title>COMPATIBILITY</title>
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<para>
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A future version of kmod will come with a strong warning to avoid use of
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the <command>install</command> as explained above. This will happen once
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support for soft dependencies in the kernel is complete. That support
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will complement the existing softdep support within this utility by
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providing such dependencies directly within the modules.
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</para>
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</refsect1>
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<refsect1><title>COPYRIGHT</title>
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<para>
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This manual page originally Copyright 2004, Rusty Russell, IBM
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Corporation. Maintained by Jon Masters and others.
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</para>
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</refsect1>
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<refsect1><title>SEE ALSO</title>
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<para><citerefentry>
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<refentrytitle>modprobe</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>modules.dep</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry>
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</para>
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</refsect1>
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</refentry>
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