insmod vs modprobe

-
Both utilities are used to load the given module

insmod
modprobe
Loads the module given
insmod /path/to/module.ko
Loads the module only in /lib/modules/$(uname -r)
modprobe /home/test/hello.ko will not work
Dependencies if present are not loaded
modprobe calculates dependencies , loads the dependencies and then the main module


How modprobe calculates dependencies?

Modprobe depends on depmod tool to calculate dependencies. depmod calculates dependencies of all the  modules present in /lib/modules/$(uname -r) folder, and places the dependency information in /lib/modules/$(uname -r)/modules.dep file

E.g. kernel/drivers/net/wireless/admtek/adm8211.ko: kernel/net/mac80211/mac80211.ko kernel/net/wireless/cfg80211.ko      kernel/drivers/misc/eeprom/eeprom_93cx6.ko

In this case, eeprom_93cx6.ko, cfg80211.ko is loaded first and then adm8211.ko

Modules are loaded right  to left and removed left to right. So while removing adm8211.ko is removed, then cfg80211.ko and finally eeprom_93cx6.ko

We can re-load the modules.dep file by running "depmod -a" command


Comments

Post a Comment

Popular posts from this blog

bb.utils.contains yocto

-
Image
bb.utils.contains  is most commonly used function in Yocto. grep in poky directory returned with 696 count. $ grep -nr 'bb.utils.contains' poky/ | wc -l 696 It's definition is present in 'poky/bitbake/lib/bb/utils.py' file This function returns third argument if the second argument is subset of the first argument else returns fourth argument Let's take an example to understand this. You can see from the above screenshot, when the second argument is a subset of first argument, "present" was returned, else "notpresent" was returned We can also use bb.utils.contains inside if loop. This we can use inside a recipe. if ${@bb.utils.contains('SOMEFLAG','NEWVALUE3','true','false',d)}; then     FOO = 'HELLO' fi
Read more

make config vs oldconfig vs defconfig vs menuconfig vs savedefconfig

-
Image
Building the Linux Kernel is a two-step process: Configuring the Kernel options Building the Kernel with those options. There are many methods available for configuring the kernel. make config: Text-based Configuration.  Options are prompted one after another. All options need to be answered Access to former options is not possible make menuconfig: Menu-driven user interface Allows to navigate forwards and backward directly between features Allows to load and save files with filenames different from ".config" Provides search feature It uses ncurses library for GUI. If the ncurses library is not installed, make menuconfig option fails. To install ncurses library on Ubuntu: sudo apt-get install libncurses5-dev make defconfig: Creates a ".config" file with default options from the ARCH supplied defconfig Configurations are generally stored in the directory: arch/$(ARCH)/configs $ ls arch/x86/configs/ i386_defconfi
Read more

PR, PN and PV Variable in Yocto

-
PN : Represents the name of the recipe. The name is usually extracted from the recipe file name. PR:  Represents the revision of the recipe. Default value for this revision is "r0". Subsequent revisions of the recipe conventionally will have "r1", "r2" and so on. PV:  Represents the version of the recipe. Normally extracted from the recipe file name. For example: ffmpeg_3.4.2.bb recipe. ${PN} : ffmpeg ${PV} : 3.4.2
Read more