From: Michael Lawnick <ml.lawnick-Mmb7MZpHnFY@public.gmane.org>
Subject: Re: rcar-i2c: always reads a byte
Date: Wed, 12 Mar 2014 09:27:47 +0100
Message-ID: <53201A83.7040605@gmx.de>
References: <531F3686.7050808@codethink.co.uk>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Return-path: <linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
In-Reply-To: <531F3686.7050808-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>
Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, SH-Linux <linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
List-Id: linux-i2c@vger.kernel.org

Hi,

Ben Dooks schrieb:
> I have noticed the following behaviour with the i2c-rcar driver
> with the following single i2c_msg structure:
>
> 	msg[0].addr = 0x12;
> 	msg[0].flags = I2C_M_RD;
> 	msg[0].len = 0;
> 	msg[0].buf = data;

isn't this illegal?
This should lead to 50% chance of blocked bus: After sending read-bit 
the slave ACK's and puts first data bit onto SDL. If it is '0', master 
won't be able to signal stop nor arbitrate the bus for other transaction 
until slave runs into internal timeout (*if* supported).
Only 9 SCL toggles will be able to free bus again.

But maybe I'm missing something.

KR
Michael