Hi Alll,
The "device driver" of the RT fifo is in fact the rt_fifo module.
This is set up such that the fifo does not exist inside the file system
until it has been "created".
Any user space calls to open the fifo will fail as you have found out.
In the standard rt fifo's package you can only create a fifo from the
real time module with rtf_create.
The zentropix package ( Yes I do work for them ) allows you to create a
fifo from a user space program.
( see ftp://www.zentropix.com/pub/downloads/rtai_rtl_fifos-05.tar.gz )
This may be of interest to you.
Quote from README.FIFOS ( zentropix fifos )
>
> To make them easier to use, fifos can now be created by the user at open time.
> If a fifo that does not exist already is opened, it is created with a 1K buffer.
> Any following creation on modules side resizes it without any loss of data.
> Again if you want to create a fifo from the user side with a desired buffer
> size you can use:
> - rtf_open_sized(const char *dev, perm, size).
>
regards
Phil Wilshire
Vasili Goutas wrote:
>
> daniel sheltraw wrote:
> >
> > Hello RT world
> >
> > Does a fifo have to be created (using rtf_create or equivalent) in
> > kernel-space before it can simply be opened for reading in user-space?
> Yes it has I think. What would youz read from it when nobody writes to
> it?
> A simple cat /dev/rtf0 tells you that there is no device like that,
> because no one created it.
>
> Vasili
>
> > The reason I ask is that I have been unable to open the /dev/rtf0 fifo in
> > user-space. I am actually running the user-space program as root
> > and the file permissions on the fifo device file are crw-r--r--.
> >
> > I am missing something simple. Please help. Thanks.
> >
> > Daniel
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