From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Wed, 19 Jun 2013 17:35:21 +0200 Subject: [Buildroot] buildroot and kernel modules In-Reply-To: <20130619152641.5DF95.59510.root@cdptpa-web08-z02> References: <20130619152641.5DF95.59510.root@cdptpa-web08-z02> Message-ID: <20130619173521.558f6d53@skate> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Dear jerryalex at tx.rr.com, On Wed, 19 Jun 2013 11:26:41 -0400, jerryalex at tx.rr.com wrote: > looking into how to enter sysbuild rules to automatically have my kernel modules loaded on bootup. > > Standard linux uses depmod to enter modules into modules.dep so that they are automatically loaded on bootup. No, that's not how it works. depmod is a tool that you run at kernel *build* time to generate modules.dep (describes dependencies between modules), modules.alias (module aliases). Those modules.* files in /lib/modules// are completely unrelated to whether modules are loaded automatically at boot or not. To get modules loaded at boot or not, you have two choices (which sometimes need to be combined together) : * Run a hotplug agent, such as udev or mdev, which will get a message from the kernel when a device appears, and load the module that implements a driver capable of handling this device. To do this, the kernel sends a description of the hardware (such as USB VID and PID) to the hotplug agent, which can run 'modprobe' with those informations, and in turn modprobe will look at modules.alias to find the corresponding module to load. This works fine if the modules to be loaded are related to some piece of hardware for which there is a proper notification from the kernel to a userspace hotplug agent. * Have a text file like /etc/modules that lists the modules to be loaded at boot, and a script in /etc/init.d/ that goes through /etc/modules and modprobes each module. > Right now our NFS file system does not have the depmod command and it appears that editing > modules.dep by hand and adding entries does not work. The depmod command is not needed at run time, only when you build the kernel and installs the modules. Editing modules.dep will not change anything in terms of automatic module loading at boot. Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com