linux-kernel - Re: [PATCH v8 05/12] media: Entity use count

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Message-ID: <4D4BF23A.1050800@maxwell.research.nokia.com>
Date:	Fri, 04 Feb 2011 14:34:02 +0200
From:	Sakari Ailus <sakari.ailus@...well.research.nokia.com>
To:	Hans Verkuil <hverkuil@...all.nl>
CC:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	alsa-devel@...a-project.org, broonie@...nsource.wolfsonmicro.com,
	clemens@...isch.de
Subject: Re: [PATCH v8 05/12] media: Entity use count

Hi,

And many thanks for the comments!

Hans Verkuil wrote:
...
>> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
>> index b82f824..114541a 100644
>> --- a/include/media/media-entity.h
>> +++ b/include/media/media-entity.h
>> @@ -81,6 +81,8 @@ struct media_entity {
>>  	struct media_pad *pads;		/* Pads array (num_pads elements) */
>>  	struct media_link *links;	/* Links array (max_links elements)*/
>>  
>> +	int use_count;			/* Use count for the entity. */
> 
> Isn't unsigned better?

Could be. The result, though, will be slightly more difficult checking
for bad use count --- which always is a driver bug.

me->use_count += change;
WARN_ON(me->use_count < 0);

we must do something like this:

if (change < 0)
	WARN_ON(me->use_count < (unsigned)-change);
me->use_count += change;

I'd perhaps also go with unsigned int; the choice for signed was made
mainly since the above check and with signed int the check was more trivial.

Regards,

-- 
Sakari Ailus
sakari.ailus@...well.research.nokia.com
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