2010-04-12 17:01:38

by Krishna Gopal

Subject: Accessing peripheral register directly from userspace

Would there be any issues for optimization purpose I do a mmap to a
peripheral register to directly access it from userspace ? This is
considering the peripheral already has a Kernel driver through which
you can set the register bit.

Basically I want to avoid the additional context switch on entering
the Kernel to set that one bit in the Peripheral register.

I request you to please share your thoughts.

Best regards,
Krishna

2010-04-13 11:37:14

by Clemens Ladisch

Subject: Re: Accessing peripheral register directly from userspace

Krishna Gopal wrote:
> Would there be any issues for optimization purpose I do a mmap to a
> peripheral register to directly access it from userspace ?

This means that userspace could access any register in the same page.

Usually this is done only with read-only pages and with devices that
are designed for this so that all accessible registers are 'safe'.


Regards,
Clemens