Subject: Re: proc_file_read() hack?
From: Thomas Hood <jdthood@mail.com>
To: Todd Inglett <tinglett@vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <3C9F69F4.3010908@vnet.ibm.com>
Content-Type: text/plain
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Date: 25 Mar 2002 14:45:55 -0500
Message-Id: <1017085557.5263.335.camel@thanatos>
Mime-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org

Unfortunately, your method #3 conflicts with methods #0 through #2,
which exhaust the range of possible values that may be returned
in *start.  Any value greater than buffer is regarded as being
"within the buffer".

Introducing method #1 was a bad idea because this hack made it
impossible cleanly to implement what you suggest.

--
Thomas Hood

On Mon, 2002-03-25 at 13:18, Todd Inglett wrote:
> How about applying my trivial patch and then adding this to your nice 
> comment?
> 
> 3) Set *start = an address outside the buffer.
>     Put the data of the requested offset at *start.
>     Return the number of bytes of data placed there.
>     If this number is greater than zero and you
>     didn't signal eof and the reader is prepared to
>     take more data you will be called again with the
>     requested offset advanced by the number ob tyes
>     absorbed.
> 
> The code should still work with the other cases now that the hack is 
> fixed.  Of course, rather than add 3), it would be better to re-word 2) 
> (e.g. "Set *start = address of the buffer which may or may not be in the 
> given buffer.).
> 
> There are cases where the data is available and need not be copied.  My 
> code got simpler when I got rid of the need to copy my data around.


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