linux-kernel - Re: [PATCH v2 06/10] mfd: tps65910: Use the standard DT property system-power-controller

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Date:	Mon, 27 Oct 2014 11:49:50 -0500
From:	Felipe Balbi <balbi@...com>
To:	Heiko Stübner <heiko@...ech.de>
CC:	<balbi@...com>, Lucas Stach <l.stach@...gutronix.de>,
	Romain Perier <romain.perier@...il.com>,
	<devicetree@...r.kernel.org>, <broonie@...nel.org>,
	<lgirdwood@...il.com>, <linux-kernel@...r.kernel.org>,
	<grant.likely@...aro.org>, <robh@...nel.org>,
	<mark.rutland@....com>, <johan@...nel.org>,
	<linux-pm@...r.kernel.org>, <linux@...ck-us.net>,
	<lee.jones@...aro.org>, <robh+dt@...nel.org>, <pawel.moll@....com>,
	<ijc+devicetree@...lion.org.uk>, <galak@...eaurora.org>,
	<linux@....linux.org.uk>, <swarren@...dotorg.org>,
	<thierry.reding@...il.com>, <gnurou@...il.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2 06/10] mfd: tps65910: Use the standard DT property
 system-power-controller

On Mon, Oct 27, 2014 at 05:49:34PM +0100, Heiko Stübner wrote:
> Am Montag, 27. Oktober 2014, 11:41:53 schrieb Felipe Balbi:
> > On Mon, Oct 27, 2014 at 05:35:49PM +0100, Lucas Stach wrote:
> > > Am Montag, den 27.10.2014, 16:26 +0000 schrieb Romain Perier:
> > > > No longer use custom property to define poweroff capability, use the
> > > > standard DT property instead.
> > > > 
> > > > Signed-off-by: Romain Perier <romain.perier@...il.com>
> > > > ---
> > > > 
> > > >  drivers/mfd/tps65910.c | 3 +--
> > > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/mfd/tps65910.c b/drivers/mfd/tps65910.c
> > > > index 7612d89..a7faff2 100644
> > > > --- a/drivers/mfd/tps65910.c
> > > > +++ b/drivers/mfd/tps65910.c
> > > > @@ -423,8 +423,7 @@ static struct tps65910_board
> > > > *tps65910_parse_dt(struct i2c_client *client,> > 
> > > >  	board_info->irq = client->irq;
> > > >  	board_info->irq_base = -1;
> > > > 
> > > > -	board_info->pm_off = of_property_read_bool(np,
> > > > -			"ti,system-power-controller");
> > > > +	board_info->pm_off = of_is_system_power_controller();
> > > > 
> > > >  	return board_info;
> > > >  
> > > >  }
> > > 
> > > You are breaking compatibility with older DTs here. This is not
> > > acceptable.
> > > 
> > > You may change all in-tree DTs to use the new property and also patch
> > > the driver to understand it, but you must make sure that the driver
> > > still understands the old, custom property. And especially in this case
> > > it isn't really hard to do.
> > 
> > correct, it should be simple to hide that under
> > of_is_system_power_controller() itself.
> 
> If I'm reading patch 1 correctly, it already does handle the generic "system-
> power-controller", as well as any foo,system-power-controller properties.

that's very true, but it doesn't handle poweroff-source which, one way
or another, will be merged into Linus' tree creating a bisection point
where things won't work.

The best solution would be for those patches to be removed from
whichever tree they are, otherwise there will always be a commit in the
mainline kernel with that binding and, even if unlikely, there will
always be the possibility of people using that commit or a developer
having to bisect an issue only to find a few commits where things don't
even build.

-- 
balbi

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