Question about register_keyboard_notifier

Question

Question about register_keyboard_notifier

GuyOded opened this issue 6 years ago · comments

GuyOded commented 6 years ago

Can you please share documentation about this function? Found none on the Internet...

Arun · Answer 1 · Mon Feb 26 2018 03:19:42 GMT+0800 (China Standard Time)

I have added a comment on what we are doing. You can find the function here:

https://elixir.bootlin.com/linux/v3.6/source/drivers/tty/vt/keyboard.c#L149

in brief, it adds a new notifier block (which has a callback function to be called when a console keyboard event happens) to a list of such blocks.

Arun · Answer 2 · Mon Feb 26 2018 03:21:24 GMT+0800 (China Standard Time)

And the notifier_block structure is here:

https://elixir.bootlin.com/linux/v3.6/source/include/linux/notifier.h#L50

Arun · Answer 3 · Mon Feb 26 2018 03:36:35 GMT+0800 (China Standard Time)

After reading your mail I realized you are trying to figure out keyboard_notifier_list.

See https://elixir.bootlin.com/linux/v3.6/source/drivers/tty/vt/keyboard.c#L143. Now ATOMIC_NOTIFIER_HEAD is a macro which is defined in

https://elixir.bootlin.com/linux/v3.6/source/include/linux/notifier.h#L103

It's a structure that initializes with an unlocked spinlock and a NULL head pointer. Once setup, when you call register_keyboard_notifier, the notifier_block struct you pass is set as the head of the list.

Arun · Answer 4 · Mon Feb 26 2018 03:38:05 GMT+0800 (China Standard Time)

When it's the kernel, in many cases you may really have to look into the code to figure out what's going on. On practice (and not necessarily on Linux kernel code only), it becomes simpler.