linux-kernel - Re: [PATCH] arm64: defconfig: Enable cros-ec and battery driver

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Date:	Fri, 27 May 2016 11:28:50 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Rhyland Klein <rklein@...dia.com>,
	Thierry Reding <treding@...dia.com>,
	Sebastian Reichel <sre@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"Dmitry Eremin-Solenikov" <dbaryshkov@...il.com>
CC:	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH] arm64: defconfig: Enable cros-ec and battery driver

Hi Krzysztof,

On 27/05/16 09:37, Krzysztof Kozlowski wrote:

...

> Indeed I was struggling with similar issue in bq27x00_battery. The issue
> was introduced by... me :(  when moving the ownership of power supply
> structure from driver to the core. However IMHO my change exposed the
> fundamental problem with power supply.
> 
> Anyway a fix for this issue was:
> 7f1a57fdd6cb6e7b (power_supply: Fix possible NULL pointer dereference on
> early uevent)
> AFAIU, this fix no longer fixes all the issues, right?
> 
> As for the fundamental problem, the power supply core should not call
> back the driver (get_property()) until the probe ends. Even if the
> di->bat was initialized, some other fields of driver could not be set
> yet. In general, the probe did not end so we should avoid calling driver
> internal functions.

For my understanding, can you elaborate why the power-supply core should
not call back to the drivers ->get_property() before the probe ends? I
assume that registering the power-supply should be the last thing done
in the probe and so the power-supply should be configured at that point.

The problems with the bq27xxx seem to stem from the periodic update of
the bq27xxx status and so it is not clear to me that this is a generic
problem for all power-supply devices.

Cheers
Jon

-- 
nvpublic