linux-kernel - Re: BQ27xxx registers

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Message-ID: <20161221131953.ntk7kuaqumq5bfjy@earth>
Date:   Wed, 21 Dec 2016 14:19:53 +0100
From:   Sebastian Reichel <sre@...nel.org>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     chris@...a.com.au, afd@...com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: BQ27xxx registers

Hi,

On Wed, Dec 21, 2016 at 01:46:17PM +0100, Pali Rohár wrote:
> On Wednesday 21 December 2016 03:49:10 Chris Lapa wrote:
> > On 20/12/16 10:34 pm, Pali Rohár wrote:
> > > On Tuesday 20 December 2016 07:00:41 Chris Lapa wrote:
> > >> I can generate a patch to fix this issue, however the bigger
> > >> problem exists as to which revision fuel gauge the
> > >> bq27xxx_battery.c driver is intended to support for each family.
> > > 
> > > Hi! I think driver should support all revisions. There can be (and
> > > probably really is) hardware which uses old revision and such
> > > hardware should be still supported...
> > 
> > I agree. However due to the register address changes across the
> > spectrum of revisions, each revision will have to be specified
> > individually. For example, we will need to implement a BQ27510G1,
> > BQ27510G2, BQ27510G3, BQ27520G1, BQ27520G2, BQ27520G3, BQ27520G4
> > definitions and prospective device tree additions ti,bq27510g1,
> > ti,bq27510g2 etc.
> > 
> > The other option is to aim for bottom of the barrel support for all
> > the devices under the BQ27500 definition but my feeling is it would
> > get messier fast and be less maintainable.
> > 
> > My preference is to go with the first option if you agree?
> 
> Yes. If those chips have different register addresses, then those chips 
> are different. Name, generation or suffix does not matter here.
> 
> Similarly there could be chips with different name, but same addresses, 
> so can use one driver/configuration without any change.
> 
> So I'm for different name in device tree (or platform data or what is 
> being used) to distinguish between different revisions.

Sounds fine to me. Let's keep the compatible string without revision
as deprecated alias for the version currently implemented by the
driver (for backward compatibility).

-- Sebastian

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