LINUX DEVICE DRIVERS

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Introduction

• Driver’s goal is map user calls to hardware or protocol related procedure
• When writing driver as a programmer, we should tell the difference between mechanism and strategy, we should not add special strategy without needed, let user use their strategy as their need.

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Build kernel

• check kernel message the message by module of linux system will be at system log directory, default: /var/log/messages, for Ubnuntu, the location of it changes to /var/log/syslog

  dmsg | tail can perform the same work too !!!

• the module need to be signed when SECURE BOOT is enabled on UEFI/BIOS setting
• remove/rebuild kernel may solve insmod error

  insmod: ERROR: could not insert module ./hello_world.ko: Invalid module format
  $ sudo apt update && sudo apt upgrade
  $ sudo apt remove --purge linux-headers-*
  $ sudo apt autoremove && sudo apt autoclean
  $ sudo apt install linux-headers-generic