linux-kernel - Re: [PATCH] power_supply: sysfs: Bring back write to writeable properties

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Date:	Wed, 10 Jun 2015 16:46:28 +0200
From:	Sebastian Reichel <sre@...nel.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] power_supply: sysfs: Bring back write to writeable
 properties

Hi,

On Mon, Jun 08, 2015 at 10:09:48AM +0900, Krzysztof Kozlowski wrote:
> The fix for NULL pointer exception related to calling uevent for not
> finished probe caused to set all writeable properties as non-writeable.
> This was caused by checking if property is writeable before the initial
> increase of power supply usage counter and in the same time using
> wrapper over property_is_writeable(). The wrapper returns ENODEV if the
> usage counter is still 0.
> 
> The call trace looked like:
>   device probe:
>     power_supply_register()
>       use_cnt = 0;
>       device_add()
>         create sysfs entries
>           power_supply_attr_is_visible()
>             power_supply_property_is_writeable()
>               if (use_cnt == 0) return -ENODEV;
>       use_cnt++;
> 
> Replace the usage of wrapper with direct call to property_is_writeable()
> from driver. This should be safe call during device probe because
> implementations of this callback just return 0/1 for different
> properties and they do not access any of the driver's internal data.

Thanks, queued.

-- Sebastian

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