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Date: Mon, 03 Nov 2014 21:01:32 +0100
From: Philippe Gerum <rpm@xenomai.org>
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Subject: Re: [Xenomai] Message Pipe services behaviour
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To: "Steve M. Robbins" <steve@sumost.ca>
Cc: Xenomai@xenomai.org

On 11/03/2014 07:37 PM, Steve M. Robbins wrote:
> On Mon, Nov 03, 2014 at 05:29:53PM +0100, Philippe Gerum wrote:
> 
>> Just to make sure we are on the same page, as Dietmar mentioned in an
>> earlier mail, read() as implemented by the rt-pipe driver only returns
>> _one_ message at a time, although > 1 could be pending. One has to
>> iterate over a read() loop using a non-blocking fd on the /dev/rtp
>> device to get them all.
> 
> Aha!  Thanks (and to Dietmar).  I completely missed this fact.  I'll
> go re-write the read as a loop and see if it works better.  I should read
> until the read() returns 0 (bytes read)?
> 

Until you get -1 with errno == EWOULDBLOCK. Zero would rather mean that
the other end of pipe has been disconnected, just like with a regular FIFO.

-- 
Philippe.