linux-kernel - Re: [PATCH/RFC v8 02/14] Documentation: leds: Add description of LED Flash class extension

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Date:	Mon, 01 Dec 2014 14:58:56 +0100
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Pavel Machek <pavel@....cz>
Cc:	linux-leds@...r.kernel.org, linux-media@...r.kernel.org,
	linux-kernel@...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: Re: [PATCH/RFC v8 02/14] Documentation: leds: Add description of LED
 Flash class extension

Hi Pavel,

On 12/01/2014 02:04 PM, Pavel Machek wrote:
> Hi!
>
>>> How are faults cleared? Should it be list of strings, instead of
>>> bitmask? We may want to add new fault modes in future...
>>
>> Faults are cleared by reading the attribute. I will add this note.
>> There can be more than one fault at a time. I think that the bitmask
>> is a flexible solution. I don't see any troubles related to adding
>> new fault modes in the future, do you?
>
> I do not think that "read attribute to clear" is good idea. Normally,
> you'd want the error attribute world-readable, but you don't want
> non-root users to clear the errors.

This is also V4L2_CID_FLASH_FAULT control semantics.
Moreover many devices clear the errors upon reading register.
I don't see anything wrong in the fact that an user can clear
an error. If the user has a permission to use a device then
it also should be allowed to clear the errors.

> I am not sure if bitmask is good solution. I'd return space-separated
> strings like "overtemp". That way, there's good chance that other LED
> drivers would be able to use similar interface...

The format of a sysfs attribute should be concise.
The error codes are generic and map directly to the V4L2 Flash
error codes.

Best Regards,
Jacek Anaszewski
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