linux-kernel - Re: [PATCH 6/6] hwmon: pwm-fan: Update the duty cycle inorder to control the pwm-fan

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87h9snvqsf.fsf@gmail.com>
Date:	Fri, 10 Apr 2015 13:25:52 -0400
From:	Ben Gamari <ben@...rt-cactus.org>
To:	Thierry Reding <thierry.reding@...il.com>,
	Sjoerd Simons <sjoerd.simons@...labora.co.uk>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Anand Moon <linux.amoon@...il.com>,
	Lukasz Majewski <l.majewski@...sung.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene@...nel.org>, devicetree@...r.kernel.org,
	"linux-samsung-soc\@vger.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, linux-pwm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Markus Reichl <m.reichl@...etechno.de>
Subject: Re: [PATCH 6/6] hwmon: pwm-fan: Update the duty cycle inorder to control the pwm-fan

Thierry Reding <thierry.reding@...il.com> writes:

> On Fri, Apr 10, 2015 at 03:30:01PM +0200, Sjoerd Simons wrote:
>> 
>> Yes/no/maybe :). Imho this is something to clarify in the pwm API
>> documentation. As currently all it says is: 
>>   "pwm_disable - stop a PWM output toggling", 
>> 
>> Which is what the exynos driver does. 
>> 
>> Thierry, could you clearify what the intention is here? I'm happy to
>> prepare a pwm driver patch if needed to solve this?
>
> I think the safest thing to do is for users to do both. You call
> pwm_config() with a zero duty cycle to make it clear what the status is
> that you want. Then you call pwm_disable() to state that you don't need
> the output signal anymore, so that any clocks needed by the PWM can be
> stopped. Doing so gives the driver the most information and should make
> the user more resilient against any possible quirks in drivers.
>
It would be great if the documentation were more clear on this matter
regardless. This is something I can imagine having to spend substantial
amounts of time Googling whereas a simple note in the documentation would
have removed all ambiguity.

Cheers,

- Ben

Download attachment "signature.asc" of type "application/pgp-signature" (473 bytes)