linux-kernel - Re: [PATCH v1 1/1] i2c: iproc: Add i2c repeated start capability

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Date:   Fri, 30 Aug 2019 14:56:26 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Rayagonda Kokatanur <rayagonda.kokatanur@...adcom.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-i2c@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Ray Jui <ray.jui@...adcom.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Lori Hikichi <lori.hikichi@...adcom.com>,
        Icarus Chau <icarus.chau@...adcom.com>,
        Shivaraj Shetty <sshetty1@...adcom.com>
Subject: Re: [PATCH v1 1/1] i2c: iproc: Add i2c repeated start capability

Hi everyone,

> +/*
> + * If 'process_call' is true, then this is a multi-msg transfer that requires
> + * a repeated start between the messages.
> + * More specifically, it must be a write (reg) followed by a read (data).
> + * The i2c quirks are set to enforce this rule.
> + */

With all the limitations in place, I wonder if it might be easier to
implement an smbus_xfer callback instead? What is left that makes this
controller more than SMBus and real I2C?

> +	/* Process the read message if this is process call */

Also, the term "process call" here seriously sounds like SMBus.

> +		addr = msg->addr << 1 | 1;

addr = i2c_8bit_addr_from_msg(msg);

> +		u32 protocol;

Hmm, another SMBus terminology.


> +	if (num > 2) {
> +		dev_err(iproc_i2c->device,
> +			"Only support up to 2 messages. Current msg count %d\n",
> +			num);
> +		return -EOPNOTSUPP;
> +	}

With your quirks flags set, the core checks it for you.

Kind regards,

   Wolfram


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