What does request_mem_region() actually do and when it is needed?

Question

I\'m studying on writing embedded linux driver, and decided to fire a few GPIOs to make sure I understand the book (LDD3, chap9.4.1) correctly.

I am able to control

Answer 1

Using request_mem_region() and ioremap() in device drivers is now deprecated. You should use the below "managed" functions instead, which simplify driver coding and error handling:

devm_ioremap()
devm_iounmap()
devm_ioremap_resource(), Takes care of both the request and remapping operations

https://bootlin.com/doc/training/linux-kernel/linux-kernel-slides.pdf slide 276