linux-kernel - Re: [PATCH 00/21] i2c: make use of i2c_8bit_addr_from

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Date:   Mon, 14 May 2018 19:01:23 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Guenter Roeck <linux@...ck-us.net>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Peter Korsgaard <jacmet@...site.dk>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-i2c@...r.kernel.org, openbmc@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org
Subject: Re: [PATCH 00/21] i2c: make use of i2c_8bit_addr_from_msg

On 2018-05-14 18:11, Joe Perches wrote:
> On Mon, 2018-05-14 at 16:53 +0200, Peter Rosin wrote:
>> Hi!
>>
>> The nice little inline i2c_8bit_addr_from_msg is not getting
>> enough use. This series improves the situation and drops a
>> bunch of lines in the process.
> 
> Perhaps the inline should test for I2C_M_REV_DIR_ADDR
> as there is at least one use like
> 
> -               addr = msg->addr << 1;
> -               if (flags & I2C_M_RD)
> -                       addr |= 1;
> +               addr = i2c_8bit_addr_from_msg(msg);
>                 if (flags & I2C_M_REV_DIR_ADDR)
>                         addr ^= 1;
> 
> which look odd

I say no, because the driver has to also indicate support with
I2C_FUNC_PROTOCOL_MANGLING and I don't see a sane way to check
that part of the contract. But what do I know. Seems orthogonal.

> Do any of these changes now no longer need
> the temporary flags variable?

Right, I thought I had made any obvious further simplification made
possible by these changes, but I overlooked that one. The flags
variable is certainly over-engineered in i2c-algo-pcf.c and would
be a good candidate for removal. But that's only patch 3/21.

I'll wait for a bit with an update, and Wolfram can adjust this on
the way in if he feels like it.

Cheers,
Peter