linux-kernel - Re: [PATCH] leds: Add mutex protection in brightness

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Date:   Wed, 9 Nov 2016 22:23:51 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Pavel Machek <pavel@....cz>,
        Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hans de Goede <hdegoede@...hat.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH] leds: Add mutex protection in brightness_show()

Hi,

On 11/09/2016 01:38 PM, Pavel Machek wrote:
> Hi!
>
>> Initially the claim about no need for lock in brightness_show()
>> was valid as the function was just returning unchanged
>> LED brightness. After the addition of led_update_brightness() this
>
> The claim was probably wrong from the day one, unless brightness is of
> type "atomic_t".
>
>              /* Ensures consistent access to the LED Flash Class device */
> 	        struct mutex            led_access;
> 		};
>
> This should really list fields that are protected by led_access.

Originally it was introduced to facilitate disabling LED subsystem
sysfs interface, i.e. it protects flags property of
struct led_classdev.

-- 
Best regards,
Jacek Anaszewski