Re: [PATCH 07/10] i2c: Add driver for AD242x bus controller

From: Wolfram Sang <wsa@the-dreams.de>
To: Luca Ceresoli <luca@lucaceresoli.net>
Cc: Daniel Mack <daniel@zonque.org>,
	linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
	linux-i2c@vger.kernel.org, alsa-devel@alsa-project.org,
	devicetree@vger.kernel.org, linux-clk@vger.kernel.org,
	mturquette@baylibre.com, sboyd@kernel.org, robh+dt@kernel.org,
	broonie@kernel.org, lee.jones@linaro.org, lars@metafoo.de,
	pascal.huerst@gmail.com
Subject: Re: [PATCH 07/10] i2c: Add driver for AD242x bus controller
Date: Thu, 12 Dec 2019 17:33:15 +0100	[thread overview]
Message-ID: <20191212163315.GA3932@kunai> (raw)
In-Reply-To: <64adf5d7-754a-f1da-aa9b-11579c5a2780@lucaceresoli.net>

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Hi Luca,

thanks for the review!

> good, but I think there's a problem in this function. A "normal"
> master_xfer function issues a repeated start between one msg and the
> next one, at least in the typical case where all msgs have the same
> slave address. Your implementation breaks repeated start. At first sight
> we might need more complex code here to coalesce all consecutive msgs
> with the same address into a single i2c_transfer() call.

Note that it is by far the standard case that all messages in a transfer
have the same client address (99,999%?). But technically, this is not a
requirement and the repeated start on the bus is totally independent of
the addresses used. It is just a master wanting to send without being
interrupted by another master.

   Wolfram

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