linux-kernel - Re: [PATCH 1/3] mfd: tps6586x: add version detection

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Message-ID: <89dbf704d8617c77259e04753e4380c9@agner.ch>
Date:	Wed, 27 Nov 2013 16:52:39 +0100
From:	Stefan Agner <stefan@...er.ch>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	swarren@...dotorg.org, thierry.reding@...il.com,
	sameo@...ux.intel.com, dev@...xeye.de, mark.rutland@....com,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] mfd: tps6586x: add version detection

Am 2013-11-27 16:30, schrieb Lee Jones:
> On Wed, 27 Nov 2013, Stefan Agner wrote:
> 
>> Am 2013-11-27 15:36, schrieb Lee Jones:
>> <snip>
>> >> Perhaps I should suggest to make TPS6586X_ANY a positive number then,
>> >> as a negative value to me indicates more of an error than a generic
>> >> parameter.
>> I see, its especially confusing since the version is filled using the
>> i2c_smbus_read_byte_data functions return value. The version field is a
>> 8-Bit value according to the data sheet, I could use 0x100 as
>> TPS6586X_ANY identifier.
> 
> How far are we away from using 0xFF?
> 
> I'd be happy to use that and change it _if_ we ever get close.
> 
> If it's likely that it'll be used, then sure 0x100 sounds okay too.

Yes, I thought about 0xFF too. The latest device we support is TPS658643
(according to data sheet release dates), which has the smallest version
number (03). Since it seems to be a CRC (hence VERSIONCRC) the number is
quite random. Also, 0xFF sounds like a bitmask which can mask all
versions, but the versions can't be used bitwise... So I would prefer to
go with 0x100.
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