Linux load driver module

Linux load driver module

Use below steps to add your driver module in linux kernel. by adding your driver as a module you can load/unload it at your convenience and will not be a part of your kernel image. I have used hello driver to explain it.

1). Create your module directory in /kernel/drivers

2). Create your file inside /kernel/drivers/hellodriver/ and add below functions and save it.

Write your driver init and exit function in hello.c file.

static int __init hello_module_init(void)
<
printk (“hello test app module init”);
return 0;
>
static int __exit hello_module_cleanup(void)

printk(“hello test app module cleanup “);
return 0;
>

module_init(hello_module_init);
module_exit(hello_module_cleanup);
MODULE_LICENSE(“GPL”);
—————————————————————————————-

3). Create empty Kconfig file and Makefile in /kernel/drivers/hellodriver/

4). Add below entries in Kconfig

config HELLOTEST_APP
tristate “HelloTest App”
depends on ARM
default m
help
hellotest app

5). Add below entries in Makefile

6). Modify the /kernel/drivers Kconfig and Makefile to support your module

7). Add below entry in /kernel/drivers/Kconfig file

8). Add below entry in /kernel/drivers/Makefile file

9). Now go to kernel directory and give

Verify that your driver module entry is visible under Device Drivers —>

For module entry it shows HelloTest App

Now recompile the kernel with your requirement and give

sudo make ARCH=arm CROSS_COMPILE=your toolchain path-

10). Check the hello.o and hello.ko files are generated at /kernel/drivers/hellodriver/

If you want to make your module as a part of kernel image then you only need to change HelloTest App the option in menuconfig and recompile the kernel.

If you don’t want to make your module as a part of kernel image then you only need to change <> HelloTest App the option in menuconfig and recompile the kernel.

This is a very simple example of adding a module in a kernel.

How to Load/Unload module/s from the user space:

In user space, you can load the module as root by typing the following into the command line. insmod load the module into kernel space.

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How to install a compiled driver (module) in Arch Linux

I have a Chuwi Hi12 tablet (x86_64 processor) and I installed ArchLinux on it. I’m trying to make sound work using default driver, but I couldn’t. So I downloaded a C written driver from here: linux-chwhi12/es8316.c I compiled it with the system included makefile and I obtained the .ko file. I don’t know how should I continue from here, so I’m asking in this forum. Thank you very much for reading and answering ______________________________________________________________- EDIT. I tried to insert the module with insmod, but it says that the resouce is busy. I don’t know how to manage it. Here are modules that refers to es8316:

snd_soc_sst_byt_cht_es8316 16384 0 - Live 0x (null) snd_soc_es8316 40960 1 - Live 0x (null) snd_soc_core 286720 3 snd_soc_sst_byt_cht_es8316,snd_soc_es8316,snd_soc_sst_atom_hifi2_platform, Live 0x (null) snd_pcm 135168 6 snd_hdmi_lpe_audio,snd_soc_sst_byt_cht_es8316,snd_soc_es8316,snd_soc_sst_atom_hifi2_platform,snd_soc_core,snd_pcm_dmaengine, Live 0x (null) 

These are default drivers installed with Arch Linux, but they doesn’t work, so I’m try to install the driver I shown

1 Answer 1

If you are testing the module, use sudo insmod .ko . Once you’ve got it installed, the .ko should live in /usr/lib/modules/$(uname -r)/ , which will allow you to do sudo modprobe

@jasonwryan is the most correct though, you should write up a PKGBUILD. I haven’t packaged a kernel module before in arch, but the wiki has a great resource on it, as always

Ok. Now I can continue. When I try to insert the module, it says that the resource is busy (I guess by other module)

you need to remove the module and all depending modules with rmmod before you can load your replacement

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How to load and unload linux drivers that are built into kernel

I want to follow the 2nd option but I do not know how to unload and load the device driver, can the open source community please help me out here !

How would you remove something that’s not built as removable module? Also, this sounds like an «XY problem» (research that term!) so it may be the wrong question you’re asking.

If there’s a way within the power cycle ,where I can unload and load device driver when its built into kernel ?

You cannot load and unload built-in device drivers, but you can «unbind» devices that are being used by drivers, and then «bind» them again afterwards. (In other words, you can cause the driver’s «remove» and «probe» handlers to be called for a device.)

1 Answer 1

It’s easy as that. You find a device and driver which you want to unbind. For example, on my Intel Minnownboard (v1) I have PCH UDC controller (a PCI device):

% lspci -nk . 02:02.4 0c03: 8086:8808 (rev 02) Subsystem: 1cc8:0001 Kernel driver in use: pch_udc 

Now I know necessary bits:

• bus on which the device is located: PCI
• device name: 0000:02:02.4 (note that lspci gives reduced PCI address, i.e. without domain or i.o.w. BDF, while driver expects domain:BDF)
• driver name: pch_udc

Take altogether we can unbind the device:

% echo 0000:02:02.4 > /sys/bus/pci/drivers/pch_udc/unbind [ 3042.531872] configfs-gadget 0000:02:02.4: unregistering UDC driver [g1] [ 3042.540979] udc 0000:02:02.4: releasing '0000:02:02.4' 

You may bind it again. Simple use bind node in the same folder.

The feature appeared more than 15 years ago and here is the article on LWN that explains it.

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What is the Linux built-in driver load order?

How can we customize the built-in driver load order (to make some built-in driver module load first, and the dependent module load later)?

4 Answers 4

Built-in drivers wont be loaded, hence built-in. Their initialization functions are called and the drivers are activated when kernel sets up itself. These init functions are called in init/main.c::do_initcalls() . All init calls are classified in levels, which are defined in initcall_levels and include/linux/init.h

These levels are actuall symbols defined in linker script ( arch/*/kernel/vmlinux.lds.* ). At kernel compile time, the linker collects all function marked module_init() or other *_initcall() , classify in levels, put all functions in the same level together in the same place, and create like an array of function pointers.

What do_initcall_level() does in the run-time is to call each function pointed by the pointers in the array. There is no calling policy, except levels, in do_initcall_level, but the order in the array is decided in the link time.

So, now you can see that the driver’s initiation order is fixed at the link time, but what can you do?

1. put your init function in the higher level, or
2. put your device driver at the higher position in Makefile

The first one is clear if you’ve read the above. ie) use early_initcall() instead if it is appropriate.

The second one needs a bit more explanation. The reason why the order in a Makefile matter is how the current kernel build system works and how the linkers works. To make a long story short, the build system takes all object files in obj-y and link them together. It is highly environment dependent but there is high probability that the linker place first object file in the obj-y in lower address, thus, called earlier.

If you just want your driver to be called earlier than other drivers in the same directory, this is simplest way to do it.

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How to install a device driver on Linux

One of the most daunting challenges for people switching from a familiar Windows or MacOS system to Linux is installing and configuring a driver. This is understandable, as Windows and MacOS have mechanisms that make this process user-friendly. For example, when you plug in a new piece of hardware, Windows automatically detects it and shows a pop-up window asking if you want to continue with the driver’s installation. You can also download a driver from the internet, then just double-click it to run a wizard or import the driver through Device Manager.

This process isn’t as easy on a Linux operating system. For one reason, Linux is an open source operating system, so there are hundreds of Linux distribution variations. This means it’s impossible to create one how-to guide that works for all Linux distros. Each Linux operating system handles the driver installation process a different way.

Second, most default Linux drivers are open source and integrated into the system, which makes installing any drivers that are not included quite complicated, even though most hardware devices can be automatically detected. Third, license policies vary among the different Linux distributions. For example, Fedora prohibits including drivers that are proprietary, legally encumbered, or that violate US laws. And Ubuntu asks users to avoid using proprietary or closed hardware.

To learn more about how Linux drivers work, I recommend reading An Introduction to Device Drivers in the book Linux Device Drivers.

Two approaches to finding drivers

1. User interfaces

If you are new to Linux and coming from the Windows or MacOS world, you’ll be glad to know that Linux offers ways to see whether a driver is available through wizard-like programs. Ubuntu offers the Additional Drivers option. Other Linux distributions provide helper programs, like Package Manager for GNOME, that you can check for available drivers.

2. Command line

What if you can’t find a driver through your nice user interface application? Or you only have access through the shell with no graphic interface whatsoever? Maybe you’ve even decided to expand your skills by using a console. You have two options:

Check if a driver is already installed

Before jumping further into installing a driver in Linux, let’s look at some commands that will determine whether the driver is already available on your system.

The lspci command shows detailed information about all PCI buses and devices on the system:

Or with grep:

$ lscpci | grep SOME_DRIVER_KEYWORD

For example, you can type lspci | grep SAMSUNG if you want to know if a Samsung driver is installed.

The dmesg command shows all device drivers recognized by the kernel:

Or with grep:

$ dmesg | grep SOME_DRIVER_KEYWORD

Any driver that’s recognized will show in the results.

If nothing is recognized by the dmesg or lscpi commands, try these two commands to see if the driver is at least loaded on the disk:

Tip: As with lspci or dmesg, append | grep to either command above to filter the results.

If a driver is recognized by those commands but not by lscpi or dmesg, it means the driver is on the disk but not in the kernel. In this case, load the module with the modprobe command:

$ sudo modprobe MODULE_NAME

Run as this command as sudo since this module must be installed as a root user.

Add the repository and install

There are different ways to add the repository through yum, dnf, and apt-get; describing them all is beyond the scope of this article. To make it simple, this example will use apt-get, but the idea is similar for the other options.

1. Delete the existing repository, if it exists.

$ sudo apt-get purge NAME_OF_DRIVER*

where NAME_OF_DRIVER is the probable name of your driver. You can also add pattern match to your regular expression to filter further.

2. Add the repository to the repolist, which should be specified in the driver guide.

$ sudo add-apt-repository REPOLIST_OF_DRIVER

where REPOLIST_OF_DRIVER should be specified from the driver documentation (e.g., epel-list).

3. Update the repository list.

4. Install the package.

$ sudo apt-get install NAME_OF_DRIVER

5. Check the installation.

Run the lscpi command (as above) to check that the driver was installed successfully.

For more information

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