linux-kernel - Reading /sys with side effects (was Re: [PATCH 1/2] Documentation: leds: Add description of LED Flash class extension)

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Message-ID: <20150127221958.GA18993@amd>
Date:	Tue, 27 Jan 2015 23:37:08 +0100
From:	Pavel Machek <pavel@....cz>
To:	Jacek Anaszewski <j.anaszewski@...sung.com>,
	Greg KH <greg@...ah.com>,
	kernel list <linux-kernel@...r.kernel.org>
Cc:	linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
	kyungmin.park@...sung.com, b.zolnierkie@...sung.com,
	cooloney@...il.com, rpurdie@...ys.net, sakari.ailus@....fi,
	s.nawrocki@...sung.com
Subject: Reading /sys with side effects (was Re: [PATCH 1/2] Documentation:
 leds: Add description of LED Flash class extension)

Hi!

> +	- flash_fault - list of flash faults that may have occurred:
> +		* led-over-voltage - flash controller voltage to the flash LED
> +			has exceededthe limit specific to the flash controller
> +		* flash-timeout-exceeded - the flash strobe was still on when
> +			the timeout set by the user has expired; not all flash
> +			controllers may set this in all such conditions
> +		* controller-over-temperature - the flash controller has
> +			overheated
> +		* controller-short-circuit - the short circuit protection
> +			of the flash controller has been triggered
> +		* led-power-supply-over-current - current in the LED power
> +			supply has exceeded the limit specific to the flash
> +			controller
> +		* indicator-led-fault - the flash controller has detected
> +			a short or open circuit condition on the indicator LED
> +		* led-under-voltage - flash controller voltage to the flash
> +			LED has been below the minimum limit specific to
> +			the flash
> +		* controller-under-voltage - the input voltage of the flash
> +			controller is below the limit under which strobing the
> +			flash at full current will not be possible. The condition
> +			persists until this flag is no longer set
> +		* led-over-temperature - the temperature of the LED has exceeded
> +			its allowed upper limit
> +
> +		Flash faults are cleared, if possible, by reading the attribute.

That's bad. Now you can no longer present flash_fault file as readable
to non-root users, and grep -ri foo /sys will interfere with your
camera application.

Bad interface, just fix it.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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