linux-kernel - Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

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Date:	Mon, 03 Feb 2014 10:43:42 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	Nathaniel Yazdani <n1ght.4nd.d4y@...il.com>,
	viro@...iv.linux.org.uk
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] epoll: read(),write(),ioctl() interface

Nathaniel Yazdani wrote:
> Using the normal I/O interface to manipulate eventpolls is much neater
> than using epoll-specific syscalls

But it introduces a _second_ API, which is epoll-specific too, and does
not use the standard semantics either.

> while also allowing for greater flexibility (theoretically, pipes could
> be used to filter access).

I do not understand this.

> read() simply waits for enough events to fill the provided buffer.

The usual semantics of read() are to return a partially filled buffer if
it would block otherwise, i.e., blocking is done only if the returned
buffer would have been empty.

> As timeout control is essential for polling to be practical, ioctl() is
> used to configure an optional timeout

This is what the timeout parameter of poll() and friends is for.


Regards,
Clemens
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