What happened when the user space application accesss device registers via mapped memory on /dev/mem?

[kipade]

Hi all,
I want to know the details of device(not physical ram device) registers via mapped memory on /dev/mem.
For example, a Soc CPU has some internal device register resources, the driver will map the memory

block to a virtual memory to kernel. But, the user application can use /dev/mem to access it(devmem2).
I want to know why? and what's happened on the backend?
Thanks.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20171207/cb57e01d/attachment.html