Linux Device Drivers in Action

LDD in action!

Drivers/Modules

Character Device Drivers

• open.c: open(2) and close(2) sample driver
  • open_test.c: open.c self test
• read.c: read(2) sample driver
  • read_test.c: read.c self test
• write.c: write(2) sample driver
  • write_test.c: write.c self test
• readv.c: readv(2) sample driver
  • readv_test.c: readv.c self test
• writev.c: writev(2) sample driver
  • writev_test.c: writev.c self test
• append.c: open(O_APPEND) sample driver
  • append_test.c: append.c self test
• scull.c: Simple Character Utility for Loading Localities driver
  • scull_test.c: scull.c self test

Debugging Primitive Test Modules

• proc.c: <linux/proc_fs.h> test module
  • proc_test.c: proc.c self test
• seq.c: <linux/seq_file.h> test module
  • seq_test.c: seq.c self test
• faulty.c: dump_stack() test module
  • faulty_test.c: faulty.c self test

Concurrency Primitive Test Modules

• sem.c: <linux/semaphore.h> test module
  • sem_test.c: sem.c self test
• rwsem.c: <linux/rwsem.h> test module
  • rwsem_test.c: rwsem.c self test
• mutex.c: <linux/mutex.h> test module
  • mutex_test.c: mutex.c self test
• comp.c: <linux/completion.h> test module
  • comp_test.c: comp.c self test
• spinlock.c: spinlock_t test module
  • spinlock_test.c: spinlock.c self test
• rwlock.c: rwlock_t test module
  • rwlock_test.c: rwlock.c self test
• kfifo.c: <linux/kfifo.h> test module
  • kfifo_test.c: kfifo.c self test
• seqlock.c: <linux/seqlock.h> test module
  • seqlock_test.c: seqlock.c self test
• rculock.c: <linux/rcupdate.h> test module
  • rculock_test.c: rculock.c self test

Advanced Character Device Drivers

• sleepy.c: <linux/wait.h> wait queue test module
  • sleepy_test.c: sleepy.c self test
• scullpipe.c: <linux/wait.h> low level wait queue test module
  • scullpipe_test.c: scullpipe.c self test
• scullfifo.c: FIFO version of the scullpipe.c
  • scullfifo_test.c: scullfifo.c self test
• poll.c: select(2), poll(2), and epoll(7) test module
  • poll_test.c: poll.c self test
• lseek.c: lseek(2) test module
  • lseek_test.c: lseek.c self test

Time, Delays, and Deferred Work

• hz.c: Exposing HZ and USER_HZ through /proc file system
  • hz_test.c: hz.c self test
• jiffies.c: Exposing jiffies, jiffies_64 and the like
  • jiffies_test.c: jiffies.c self test
• jitbusy.c: Busy wait based delay module
  • jitbusy_test.c: jitbusy.c self test
• jitsched.c: Schedule based delay module
  • jitsched_test.c: jitsched.c self test
• jitqueue.c: Wait queue based delay module
  • jitqueue_test.c: jitqueue.c self test
• jitimer.c: Kernel timer based delay module
  • jitimer_test.c: jitimer.c self test
• jitasklet.c: Tasklet based delay module
  • jitasklet_test.c: jitasklet.c self test
• jiwq.c: Work queue based delay module
  • jiwq_test.c: jiwq.c self test

Memory related modules

• alloc.c: Various memory allocation functionalities, kmalloc, vmalloc etc.
  • alloc_test.c: alloc.c self test
• scullc.c: Scull backed by the lookaside cache
  • scullc_test.c: scullc.c self test

Build

$ make
make -C /lib/modules/5.0.6.1/build M=/home/kei/git/ldd modules
make[1]: Entering directory '/home/kei/src/linux-5.0.6'
  CC [M]  /home/kei/git/ldd/scull.o
  CC [M]  /home/kei/git/ldd/sleepy.o
  CC [M]  /home/kei/git/ldd/ldd.o
  CC [M]  /home/kei/git/ldd/sculld.o
  Building modules, stage 2.
  MODPOST 4 modules
  CC      /home/kei/git/ldd/ldd.mod.o
  LD [M]  /home/kei/git/ldd/ldd.ko
  CC      /home/kei/git/ldd/scull.mod.o
  LD [M]  /home/kei/git/ldd/scull.ko
  CC      /home/kei/git/ldd/sculld.mod.o
  LD [M]  /home/kei/git/ldd/sculld.ko
  CC      /home/kei/git/ldd/sleepy.mod.o
  LD [M]  /home/kei/git/ldd/sleepy.ko
make[1]: Leaving directory '/home/kei/src/linux-5.0.6'

Test

$ sudo make run_tests
make -C /lib/modules/5.0.6.1/build M=/home/kei/git/ldd modules_install
make[1]: Entering directory '/home/kei/src/linux-5.0.6'
  INSTALL /home/kei/git/ldd/ldd.ko
  INSTALL /home/kei/git/ldd/scull.ko
  INSTALL /home/kei/git/ldd/sculld.ko
  INSTALL /home/kei/git/ldd/sleepy.ko
  DEPMOD  5.0.6.1
make[1]: Leaving directory '/home/kei/src/linux-5.0.6'
for mod in scull sleepy ldd sculld; do modprobe $mod; done
make -C tests top_srcdir=/lib/modules/5.0.6.1/build OUTPUT=/home/kei/git/ldd/tests \
        CFLAGS="-I/lib/modules/5.0.6.1/build/tools/testing/selftests -I/home/kei/git/ldd" run_tests
make[1]: Entering directory '/home/kei/git/ldd/tests'
TAP version 13
selftests: tests: sculld_test
========================================
Pass 44 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..44
ok 1..1 selftests: tests: sculld_test [PASS]
selftests: tests: sleepy_test
========================================
Pass 3 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..3
ok 1..2 selftests: tests: sleepy_test [PASS]
selftests: tests: ldd_test
========================================
Pass 2 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..2
ok 1..3 selftests: tests: ldd_test [PASS]
selftests: tests: scull_test
========================================
Pass 28 Fail 0 Xfail 0 Xpass 0 Skip 0 Error 0
1..28
ok 1..4 selftests: tests: scull_test [PASS]
make[1]: Leaving directory '/home/kei/git/ldd/tests'

Cleanup

sudo make clean

Happy Hacking!