To test the code presented in the recipe in the chapter and to show how everything works, we have to compile it before any further steps are taken:
$ make KERNEL_DIR=../../../linux
make -C ../../../linux \
ARCH=arm64 \
CROSS_COMPILE=aarch64-linux-gnu- \
SUBDIRS=/home/giometti/Projects/ldddc/github/chapter_4/chrdev modules
make[1]: Entering directory '/home/giometti/Projects/ldddc/linux'
CC [M] /home/giometti/Projects/ldddc/github/chapter_4/chrdev/chrdev.o
CC [M] /home/giometti/Projects/ldddc/github/chapter_4/chrdev/chrdev-req.o
...
LD [M] /home/giometti/Projects/ldddc/github/chapter_4/chrdev/chrdev.ko
make[1]: Leaving directory '/home/giometti/Projects/ldddc/linux'
Then, we have to move the chrdev.ko and chrdev-req.ko files to the ESPRESSObin. Now, if we insert the first module...