linux-kernel - Re: [PATCH v11 5/8] i2c: fsi: Add transfer implementation

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Message-Id: <d7128886-148f-d255-fb33-3727cad01569@linux.vnet.ibm.com>
Date:   Tue, 10 Jul 2018 12:52:58 -0500
From:   Eddie James <eajames@...ux.vnet.ibm.com>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org,
        benh@...nel.crashing.org, joel@....id.au, mark.rutland@....com,
        gregkh@...uxfoundation.org, rdunlap@...radead.org,
        andy.shevchenko@...il.com, peda@...ntia.se
Subject: Re: [PATCH v11 5/8] i2c: fsi: Add transfer implementation



On 07/09/2018 05:41 PM, Wolfram Sang wrote:
>> +	cmd |= FIELD_PREP(I2C_CMD_ADDR, msg->addr >> 1);
> I just noticed this and wonder: Don't you need the LSB of the address?
> It is not the RW flag, this is encoded in msg->flags.

So, the hardware interprets the LSB as the RW flag. It wouldn't be 
possible to have a device addressed with the LSB set on this I2C master.

>
> Also, no seperate handling for 10 bit addresses? Technically, 7-bit 0x50
> is different on the wire from 10-bit 0x050. This is minor, though. There
> are no 10-bit devices out there. Still, did you test 10-bit support?

Indeed, real 10-bit addresses require some additional manipulation of 
this I2C master in order to work. We don't support it right now.

Thanks,
Eddie

>
> Rest looks good.
>