linux-kernel - Re: [PATCH] regmap: Fix i2c word access when using SMBus access functions

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Date:	Tue, 03 Feb 2015 06:21:45 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Mark Brown <broonie@...nel.org>
CC:	Lars-Peter Clausen <lars@...afoo.de>,
	Robert Rosengren <robert.rosengren@...s.com>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jean Delvare <jdelvare@...e.de>
Subject: Re: [PATCH] regmap: Fix i2c word access when using SMBus access functions

On 02/03/2015 03:42 AM, Mark Brown wrote:
> On Mon, Feb 02, 2015 at 06:30:02AM -0800, Guenter Roeck wrote:
>> On 02/02/2015 03:56 AM, Mark Brown wrote:
>
>>> Yes, we really ought to handle _NATIVE too (though the chances of it
>>> being used with I2C are minimal, it's mostly for MMIO).  This also feels
>
>> Well, we do; it is handled similar to the big endian case with the current
>> code. Do you think it should be handled differently ? If yes, how ?
>
> Perhaps it just needs to be more explicit about how it's handling native
> endian?  I didn't spot it.
>
Thinking about it, we should actually reject requests for _NATIVE. SMBus
16 bit accesses are either little endian or big endian.

>>> like it's something that should be being handled further up the stack in
>>> the serialization code but given that there's direct functions for this
>>> in the smbus code perhaps it's better here.  Or perhaps the smbus
>>> support ought to be transitioned to use the bus interface and set
>>> reg_write() and reg_read() operations now that we can do that, it seems
>>> like a better fit though it might break compatibility with wierd devices.
>
>> I thought about that, but since the smbus functions perform endianness
>> conversion it would mean that I would have to undo that conversion just
>> to have it done again.
>
> No, the whole point is that by doing this you avoid any endianness
> conversions or formatting in the framework at all so you can just use
> the smbus functions to handle the formatting.
>
Ah, guess I got confused. The SMBus accesses are already using reg_read
and reg_write.

Thanks,
Guenter

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