Philippe Gerum wrote:
On Mon, 2011-02-21 at 18:54 +0100, varname wrote:
trying to write a simple producer / consumer using message pipes in
the native API, this phrase from the documentation (found here [1])
confuses me:
"-EPIPE is returned if the associated special device is not yet open."
It's not so much the sentence itself, but more the fact that I'm not
getting that return value from rt_pipe_stream() when streaming bytes
to a RT_PIPE that hasn't had its "special device" opened in secondary
domain.
I've attached a modified trivial-periodic.c that demonstrates what I'm
seeing. Afaik there is nothing open(2)-ing the /dev/rtp9 in the
secondary domain. All writes succeed, up to about write 31 (*1024),
after which all writes return 0.
[..]
wrote: 1024, res: 1024
wrote: 1024, res: 948
wrote: 1024, res: 0
wrote: 1024, res: 0
[..]
Is the documentation incorrect, or am I misunderstanding something?
The doc is wrong (former implementation, 2.1.x series), the pipe
services do buffer real-time output until the special device is
eventually opened starting with Xenomai 2.2.x. Since you are using
rt_pipe_stream(), the output is directed to an internal buffer until
there is no more space there, which causes the final 0-byte returns.
So everything looks ok, except the doc.
ok, so there is actually no way to detect whether or not the special
device has been opened? As I understood from earlier mails on the list,
writes to a full pipe buffer just fail, correct?
Is there any way to flush a message pipe from a userspace task (as
opposed to a kernelspace one, where rt_pipe_flush is available)?
thanks for the swift reply
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