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

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Date:   Tue, 10 Jul 2018 20:50:43 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Eddie James <eajames@...ux.vnet.ibm.com>
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


> > > +	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.

But msg->addr is 7 bit and LSB aligned. If I am not horribly wrong, with
the above code, an EEPROM at 0x50 would show up as 0x28 with your
driver?

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

Then you should remove the associated FUNC flag.


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