Hello Lothar,
I am currently working on a POSIX like aio module for RTAI. The
module uses a number of kernel threads (basicly non realtime user
programms
running in kernel space) to do the IO via the sys_* functions.
The communication between realtime and non realtime is based on LXRT
(and with that not available for RT-linux but only for RTAI).
the sys_* functions have a few problems, first they aren't exported by
the
standard kernel so you have to add the EXPORT_SYMBOL(...) to the ksyms.c
file,
and recompile. Secondly they check if the arguments are valid, which
they aren't
when calling form kernelspace, to work around that one has to play
around
a bit with the segment descriptors.
BTW: RTAI supports rt_malloc rt_free which allows you to malloc and free
from realtime (under controled conditions). When your application needs
a lot of this and needs to write and read files a lot LXRT might be a
nice solution for you.
MfG,
Erwin
Lothar Krause wrote:
>
> Hello
>
> AFAIG one can't use the usual open, read & write calls or alloc memory
> within realtime threads. Okay, but one can use kmalloc() in init_module()
> the question now is: Whats about file access in init_module() ? One could use
> sys_read() sys_write() etc. to do this, no?
>
> Did anyone tried similiar or is there some reason that renders this approch
> useless?
>
> lothar
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