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Pollable sysfs attributes

After running make command, there will be one module:

  • sysfs-poll.ko

After loading the module, this will create two sysfs attributes in /sys/hello:

  • /sys/hello/trigger
  • /sys/hello/notify
# insmod ./sysfs-poll.ko

# ls -l /sys/hello/
total 0
-rw-r--r-- 1 root root 4096 oct.  13 11:54 notify
-rw-r--r-- 1 root root 4096 oct.  13 11:54 trigger

For testing, one can build either compile either the file sysfs-select-user.c or sysfs-poll-user.c.

$ gcc sysfs-select-user.c -o sysfs-select

Now one should execute sysfs-select binary as sudo:

# sudo ./sysfs-select 

Open another console, and then write anything into either /sys/hello/trigger or /sys/hello/notify.

# echo "john" > /sys/hello/trigger

The app wainting will then print something like:

# sudo ./sysfs-select 
Change detected in /sys/hello/trigger

Same for writing in /sys/hello/notify (in console 1):

# echo "john" > /sys/hello/notify

which will produce below output (in console 2):

# ./sysfs-select 
Change detected in /sys/hello/notify

Additionally, one can use dmesg command for debug messages.

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