amitesh-singh / ldd

Linux Device Drivers samples

ldd tips/setups

minimal setup on ubuntu 16.04

apt-get source linux-image-$(uname -r) in /usr/src in case you are going to run your kernel
sudo apt-get build-dep linux-image-$(uname -r)
sudo apt-get install kernel-package

rpi2

The below stuff did not work, so don't try it. sudo apt-get install linux-image-rpi-rpfv linux-headers-rpi-rpfv

use rpi-update (do update it)
$ sudo rpi-update
It should give you the latest kernel and then reboot.

After that, Get rpi-source
$ sudo wget https://raw.githubusercontent.com/notro/rpi-source/master/rpi-source -O /usr/bin/rpi-source
$ sudo chmod +x /usr/bin/rpi-source
$ /usr/bin/rpi-source -q --tag-update
$ rpi-source

how to build kernel on ubuntu

http://www.howtogeek.com/howto/ubuntu/how-to-customize-your-ubuntu-kernel/

make menuconfig - arrow keys were not working. the issue was with bash. to make it work, issue sh command and then make menuconfig should work.

sudo apt-get install libqt4-dev
#cd linux-xxx/
#cp /boot/config-uname -r .config
#make xconfig
# make-kpkg clean
$ fakeroot make-kpkg --initrd --append-to-version=-custom kernel_image kernel_headers

two .deb files are generated. one is linux image and other is linux headers.
install both .deb files. those are located in parent dir.
dpkg -i linux.deb and then reboot.
check uname -r after reboot.

Aug 27 01:19:03 ami-desktop kernel: [ 0.000000] Hello to ami's kernel log file to be checked for boot logs: /var/log/kern.log

how to remove the custom kernel

installed kernel via sudo make install

1. locate 2.6.28.9-custom
2. delete the files manually and then sudo update-grub2

To uninstall custom kernel, make sure you are not using that kernel currently.

installed kernel in debian way,

dpkg --list | grep kernel-image
sudo apt-get remove kernel-image-your-kernel-image
To see all the kernels list in grub bootloader screen, press SHIFT key.

how to load/unload ldds

insmod hello.ko --> insert the module
lsmode -> list all the loaded modules
rmmod hello -> remove the loaded module if present

modinfo hello.ko -> gives info abt that module

dmesg | tail -f -> to check the printk() output

Tips

1. how to login as root in ubuntu first change the password of root (if u r doing it for first time) sudo passwd root
   //change the password
   //to login into root, do
   su root

All compiled modules are in /lib/modules/uname -r/kernel/drivers/

Links

best one: http://www.tldp.org/LDP/lkmpg/2.6/html/x569.html#AEN687

1. http://lwn.net/Kernel/LDD3/
2. https://github.com/martinezjavier/ldd3/
3. http://lwn.net/Articles/2.6-kernel-api/
4. http://opensourceforu.efytimes.com/2015/05/writing-a-basic-framebuffer-driver/
5. https://sysplay.in/ -> interesting way
6. http://www.tutorialsdaddy.com/2015/05/writing-character-device-driver/
7. https://appusajeev.wordpress.com/2011/06/18/writing-a-linux-character-device-driver/
8. http://derekmolloy.ie/writing-a-linux-kernel-module-part-1-introduction/
9. https://fabiobaltieri.com/2011/09/21/linux-led-subsystem/
10. https://0xax.gitbooks.io/linux-insides/content/ --> best one
11. http://linux-sunxi.org/SPIdev
12. nice doc on writing spi driver - http://invo-tronics.com/spi-driver-for-linux-based-embedded-system/

how to implement icotls on a char driver

http://linux.die.net/lkmpg/x892.html https://fabiobaltieri.com/2012/05/20/linux-kernel-device-drivers-for-avr-v-usb-devices/

how to check module info using objdump

modinfo module.ko or objdump hello-1.ko --full-contents --section=.modinfo

how to send kernel patches

install mutt

sudo apt-get install mutt

Raise the patch

mutt -H 001....path
OR

install git-send-email

sudo apt-get install git-email

Raise the patch

git format-patch HEAD^
git send-email --to <email address> --cc [email protected] --cc [email protected] --cc [email protected] 001....patch

nice ascii flow diagram: http://asciiflow.com/ useful while sending RFCs
Reference: https://burzalodowa.wordpress.com/2013/10/05/how-to-send-patches-with-git-send-email/

how to make doc

make htmldocs

How to fix kernel module warnings

1. kernel module signature loading failed: Add
   CONFIG_MODULE_SIG=n
   in your module Makefile

Linux interrupts

1. http://www.slideshare.net/kerneltlv/linux-interrupts-63978201?qid=aba0244c-f180-42f6-a9ad-e5791dda14db&v=&b=&from_search=5

Device Tree

• https://events.linuxfoundation.org/sites/events/files/slides/petazzoni-device-tree-dummies.pdf
• install sudo apt install device-tree-compiler @ dtc

how to compile latest kernel

Ubuntu

cd linux-stable

cp /boot/config-uname -r .config

yes '' | make oldconfig

make menuconfig
make clean

make -j getconf _NPROCESSORS_ONLN deb-pkg LOCALVERSION=-custom

You’ll find your new kernel packages one directory up. They’ll be easily identifiable by their version number

cd ..
sudo dpkg -i linux-firmware-image-4.11.1-custom_4.11.1-custom-1_amd64.deb
sudo dpkg -i linux-libc-dev_4.11.1-custom-1_amd64.deb
sudo dpkg -i linux-headers-4.11.1-custom_4.11.1-custom-1_amd64.deb
sudo dpkg -i linux-image-4.11.1-custom-dbg_4.11.1-custom-1_amd64.deb
sudo dpkg -i linux-image-4.11.1-custom_4.11.1-custom-1_amd64.deb

then reboot

Arch linux

cd linux-src
zcat /proc/config.gz > .config
yes '' | make oldconfig
make menuconfig
make clean
make -j getconf _NPROCESSORS_ONLN LOCALVERSION=-custom
make modules_install

make modules_install

Copy the kernel to /boot directory
cp -v arch/x86_64/boot/bzImage /boot/vmlinuz-linux414

Make initial RAM disk
cp /etc/mkinitcpio.d/linux.preset /etc/mkinitcpio.d/linux414.preset sudo vim /etc/mkinitcpio.d/linux414.preset

... ALL_kver="/boot/vmlinuz-linux48"
...
default_image="/boot/initramfs-linux48.img"
...
fallback_image="/boot/initramfs-linux48-fallback.img"

Finally, generate the initramfs images for the custom kernel in the same way as for an official kernel:
mkinitcpio -p linux414

Copy System.map

The System.map file is not required for booting Linux. It is a type of "phone directory" list of functions in a particular build of a kernel. The System.map contains a list of kernel symbols (i.e function names, variable names etc) and their corresponding addresses. This "symbol-name to address mapping" is used by:

cp System.map /boot/System.map-YourKernelName ln -sf /boot/System.map-YourKernelName /boot/System.map

After completing all steps above, you should have the following 3 files and 1 soft symlink in your /boot directory along with any other previously existing files:

Kernel: vmlinuz-YourKernelName
Initramfs: Initramfs-YourKernelName.img
System Map: System.map-YourKernelName
System Map kernel symlink

grub-mkconfig -o /boot/grub/grub.cfg

and then reboot

Rpi3 - arch linux

• pacman -S linux-headers
  choose 14) linux-raspberry-headers

ldd's Issues

Cannot thank you enuff!

Im an older guy, and decided id learn programming, and wanted to do it with mcu's and linix kernel...Ive only been able to learn from examples and so so few examples of both mcu paired with linux kernel drivers! You are not only one of the very few resources but the best by a hhuge margin!! i was able to take the ldd examples and sum other pieces of your code and add usb gpio with irq! to the i2c-star also a led controller driver, pwm, and random other things. Tho ive been able to use endpoint 0 successfully, and actually either my interrupt endpoint for orq firmware is either broken and only reason it worked or all others ive tried are lol but ill get it eventually. Bit i litterally know nothing about coding and have with much determination been able to Forest Gump my way into sum cool stuff, and all because of you! Thank you from bottom of my heart i hope you know how important what you have done is to sum of us. I oonly had the one stm32/libopencm3 example of ypur if any more exist please point them out! id love to see a working firmware and driver for that pairing using bulk/interrupt endpoints. Sorry i put this in issues but i couldnt find the button for "tell this man hes a living legend and a god who us mere mortals shall bow too!" but ill keep looking