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Date: Wed, 9 Nov 2005 14:00:55 -0800
From: Andrew Morton <akpm@osdl.org>
To: Tom Zanussi <zanussi@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, karim@opersys.com
Subject: Re: [PATCH 2/4] relayfs: Documentation for non-relay file support
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Tom Zanussi <zanussi@us.ibm.com> wrote:
>
>  +relay_open() automatically creates files in the relayfs filesystem to
>  +represent the per-cpu kernel buffers; it's often useful for
>  +applications to be able to create their own files in the relayfs
>  +filesystem as well e.g. 'control' files used to communicate control
>  +information between the kernel and user sides of a relayfs
>  +application.

What are the semantics of these control files?  How does an application
know that there's something new to be read from them?  select() or poll()
or blocking read()?

Can userspace write to the control files?   If so, what happens in-kernel?