Re: [Xenomai-help] rt_io_get_region

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Roger Carns wrote:
> 
> On 10/11/2010 3:18 PM, Gilles Chanteperdrix wrote:
>> Roger Carns wrote:
>>> Does rt_io_get_region function be called from user space and does
>>> it return a user space address and if so how is it return? Also
>>> is there doc out there someplace on usage of this function.
>> rt_io_get_region is a user-space mapping of 
>> request_mem_regio/request_io_region. As such, yes, it may be called
>> from user-space. And no, it does not return address. What it
>> returns is a cookie that may be passed to rt_io_put_region to free
>> the used memory.
>> 
>> In order to map an MMIO region in user-space you should use
>> /dev/mem or use ioperm and inl/outl directly if you want to access
>> an I/O port. What rt_io_get_region does is to allow you to this
>> cleanly with regard to the rest of the system.
>> 
> So, I open the /dev/mem and use the fd returned on the mmap call. But
> how do I associate the region defined in the rt_io_get_region with
> that fd?

The offset passed to mmap is the physical address which you want to map.

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-- 
                                                                Gilles.