From RTEMS to Linux :-(

[Joel Sherrill]

On 03/23/2010 12:57 PM, Leon Pollak wrote:
> On Tuesday March 23 2010, Gedare Bloom wrote:
>    
>> Linux programs are mainly stuck with the POSIX API to the kernel and
>> whatever you can find in libraries (libc, etc) -- which are usually
>> built on top of POSIX. Certain types of low-level operations, such as
>> allocating physically contiguous memory, is not (to my knowledge)
>> possible from within a user-land application and is not specified by
>> POSIX.  There are kernel interfaces that provide such operations for
>> kernel-mode code such as device drivers and kernel modules, but I
>> don't think there are any user API functions to access them.
>>
>> I would suggest formulating a set of questions specific to what you
>> are trying to do, and then ask them on some appropriate Linux mailing
>> lists (e.g. http://www.linux.org/docs/lists.html and
>> linux-c-programming).  My guess is that most of the functionality you
>> need is available somewhere in some library, but the trick is how to
>> find it.  If you do need low-level functionality (i.e. hardware
>> dependent) then you will probably have to write a kernel device
>> driver.  There are also good resources online for how to do this, for
>> example http://lwn.net/Kernel/LDD3/
>>      
> Thank you, Gedare.
>
> No, I almost do not need to do low level programming (and I understand just
> for now how to do it). My user space main program is in processing of data
> received from low level driver in several stages.
> In RTEMS I should do it simple: create a partition, pull the buffer, give it
> to the driver to fill, pass it to the processing task(s) and free it at the
> end.
> I found POSIX threads (look a bit awkward from RTEMS task point of view, but
> still usable), mailboxes and signals (analog of semaphores?). But no traces of
> something similar to partitions....
> This made me think that I am on the wrong way...
>    

A partition is internally just an rtems chain.  So you could mimic
this easily enough by just bring the chain code over to Linux.  I have
done that myself in the past.

--joel


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Joel Sherrill, Ph.D.             Director of Research&  Development
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