linux-kernel - Re: [PATCH v5 2/3] i2c: iproc: Add Broadcom iProc I2C Driver

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Date:	Sun, 18 Jan 2015 13:13:30 +0100
From:	Arend van Spriel <arend@...adcom.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	Mark Rutland <mark.rutland@....com>, <devicetree@...r.kernel.org>,
	"Ian Campbell" <ijc+devicetree@...lion.org.uk>,
	Florian Fainelli <f.fainelli@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Scott Branden <sbranden@...adcom.com>,
	Wolfram Sang <wsa@...-dreams.de>, Ray Jui <rjui@...adcom.com>,
	Christian Daudt <bcm@...thebug.org>,
	<linux-kernel@...r.kernel.org>, Matt Porter <mporter@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	<bcm-kernel-feedback-list@...adcom.com>,
	<linux-i2c@...r.kernel.org>, "Kumar Gala" <galak@...eaurora.org>,
	Grant Likely <grant.likely@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 2/3] i2c: iproc: Add Broadcom iProc I2C Driver

On 01/18/15 12:56, Uwe Kleine-König wrote:
> Hello,
>
> On Sun, Jan 18, 2015 at 12:46:51PM +0100, Arend van Spriel wrote:
>> On 01/18/15 12:17, Uwe Kleine-König wrote:
>>> Hello Wolfram,
>>>
>>> On Sun, Jan 18, 2015 at 12:06:58PM +0100, Wolfram Sang wrote:
>>>> On Sun, Jan 18, 2015 at 10:47:41AM +0100, Uwe Kleine-König wrote:
>>>>> On Sun, Jan 18, 2015 at 10:14:04AM +0100, Arend van Spriel wrote:
>>>>>> On 01/17/15 00:42, Ray Jui wrote:
>>>>>>> +	complete_all(&iproc_i2c->done);
>>>>>>
>>>>>> Looking over this code it seems to me there is always a single
>>>>>> process waiting for iproc_i2c->done to complete. So using complete()
>>>>>> here would suffice.
>>>>> Yeah, there is always only a single thread waiting. That means both
>>>>> complete and complete_all are suitable. AFAIK there is no reason to pick
>>>>> one over the other in this case.
>>>>
>>>> Clarity?
>>> And which do you consider more clear? complete_all might result in the
>>> question: "Is there>1 waiter?" and complete might yield to "What about
>>> the other waiters?". If you already know there is only one, both are on
>>> par on clarity. Might only be me?! I don't care much.
>>
>> Maybe it is me, but it is not about questions but it is about
>> implicit statements that the code makes (or reader derives from it).
>> When using complete_all you indicate to the reader "there can be
>> more than one waiter". When using complete it indicates "there is
>> only one waiter". If those statements are not true that is a code
> No, complete works just fine in the presence of>1 waiter. It just wakes
> a single waiter and all others continue to wait.

Yes. Agree.

> That is, for single-waiter situations there is no semantic difference
> between complete and complete_all. But there is a difference for
> multi-waiter queues.

Indeed.

> I think this is just a matter of your POV in the single-waiter
> situation: complete might be intuitive because you just completed a
> single task and complete_all might be intuitive because it signals
> "I'm completely done, there is noone waiting for me any more.".

Ok. Let's leave it to the author's intuition or to say it differently 
"sorry for the noise" ;-)

Regards,
Arend

> Best regards
> Uwe
>

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