linux-kernel - Re: iio: dht11 broken

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Message-ID: <547C78BF.3030709@nod.at>
Date:	Mon, 01 Dec 2014 15:18:39 +0100
From:	Richard Weinberger <richard@....at>
To:	Linus Walleij <linus.walleij@...aro.org>
CC:	Harald Geyer <harald@...ib.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Alexandre Courbot <acourbot@...dia.com>,
	Stephen Warren <swarren@...dia.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: iio: dht11 broken

Am 01.12.2014 um 15:08 schrieb Linus Walleij:
> On Mon, Dec 1, 2014 at 11:59 AM, Richard Weinberger <richard@....at> wrote:
>> Am 01.12.2014 um 11:49 schrieb Harald Geyer:
> 
>>> Any input from gpiolib people about what the proper fix would be in
>>> their opinion, of course is appreciated. I don't think the dht11 driver
>>> is doing anything unreasonable per se, so maybe they can clarify how
>>> the API is intended to be used?
>>
>> Your driver sets up a GPIO as IRQ and then you switch the mode to output
>> to enable the DHT sensor.
>> This is not an API issue, it is an design issue.
>> I'm not a hardware expert but AFAIK setting an IRQ pin into output mode can
>> lead to undefined behavior.
> 
> Well that check is there exactly to prevent madness like this.
> 
> IRQs on pins set to output *does* *not* *make* *sense*.
> 
> Remove the IRQ before setting the pin to output and vice
> versa and everyone will be happier.

Thanks for the confirmation.
I'll cook up a patch.

Thanks,
//richard
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