linux-kernel - Re: [PATCH -next v4 1/3] regmap: add SCCB support

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Date:   Wed, 18 Jul 2018 17:28:32 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Akinobu Mita <akinobu.mita@...il.com>
Cc:     linux-media@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Peter Rosin <peda@...ntia.se>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: Re: [PATCH -next v4 1/3] regmap: add SCCB support

On Tue, Jul 17, 2018 at 12:47:48AM +0900, Akinobu Mita wrote:
> This adds Serial Camera Control Bus (SCCB) support for regmap API that
> is intended to be used by some of Omnivision sensor drivers.
> 
> The ov772x and ov9650 drivers are going to use this SCCB regmap API.
> 
> The ov772x driver was previously only worked with the i2c controller
> drivers that support I2C_FUNC_PROTOCOL_MANGLING, because the ov772x
> device doesn't support repeated starts.  After commit 0b964d183cbf
> ("media: ov772x: allow i2c controllers without
> I2C_FUNC_PROTOCOL_MANGLING"), reading ov772x register is replaced with
> issuing two separated i2c messages in order to avoid repeated start.
> Using this SCCB regmap hides the implementation detail.
> 
> The ov9650 driver also issues two separated i2c messages to read the
> registers as the device doesn't support repeated start.  So it can
> make use of this SCCB regmap.

Cool, this series really gets better and better each time. Thank you for
keeping at it! And thanks to everyone for their suggestions. I really
like how we do not introduce a couple of i2c_sccb_* functions with a
need to export them. And given the nature of regmap, I'd think it should
be fairly easy to add support for ov2659 somewhen which has 16 bit
registers? Only minor nits:

> +#include <linux/regmap.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>

Sort these?

> +/**
> + * regmap_sccb_read - Read data from SCCB slave device
> + * @context: Device that will be interacted wit

"with"

> +	ret = __i2c_smbus_xfer(i2c->adapter, i2c->addr, i2c->flags,
> +			       I2C_SMBUS_WRITE, reg, I2C_SMBUS_BYTE, NULL);

Mark: __i2c_smbus_xfer is a dependency on i2c/for-next. Do you want an
immutable branch for that?

> +/**
> + * regmap_sccb_write - Write data to SCCB slave device
> + * @context: Device that will be interacted wit

"with"

But in general (especially for the I2C parts):

Reviewed-by: Wolfram Sang <wsa+renesas@...g-engineering.com>


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