linux-kernel - Re: [PATCH v6 07/19] i2c: octeon: Use i2c recovery framework

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Message-ID: <20160421175110.GA2710@hardcore>
Date:	Thu, 21 Apr 2016 19:51:10 +0200
From:	Jan Glauber <jan.glauber@...iumnetworks.com>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	<linux-kernel@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	David Daney <ddaney@...iumnetworks.com>
Subject: Re: [PATCH v6 07/19] i2c: octeon: Use i2c recovery framework

On Thu, Apr 21, 2016 at 03:54:50PM +0200, Wolfram Sang wrote:
> 
> > I assumed this check was bogus and there are no valid 0-length
> > messages...
> 
> They are valid (check SMBUS_QUICK), but not every controller can handle
> them correctly. Your driver has SMBUS_QUICK enabled, so this is a
> contradiction to the check above where it rejects it.

Oops, this mismatch dates back to the inital driver code. From the
documentation I would say SMBUS_QUICK is not supported, although nothing
terrible happens in the write case.

> So, it looks like it needs to be tested again (and documented this
> time). If the HW can't do it, the FUNC bit for QUICK needs to be masked
> out. If it can do SMBUS_QUICK, the check can probably go away.
> 

I would like to disable SMBUS_QUICK. It never worked for the read case.
Could we break something by disabling the quick-write case or is
the quick-write emulated by a larger write if the feature bit is not
set?