Confusion about memory mapped I/O

[Benoit Donnette]

> Hi,
>
> I am trying to understand the magic behind memory mapped I/O in linux
> device drivers. I understand the concepts behind setting up memory
> mapped I/O but I am confused about how the data (once written into
> memory) gets transferred onto the bus and onto the peripheral.

"Memory mapped I/O" means taht through the specified address, mapped in
the address space, you actually send data to the device.

It means you map I/O buffers on the device into addressable memory. After
that, everything you write at these addresses will go to the device as set
up, not to memory.

>
> E.g. many network drivers use memory mapped I/O and this makes it quite
> generic but how do you specify the bus in all this?

All the memory mapped I/O setup does the job.

>
> Thanks for any help,
> Amit
>