linux-kernel - Re: [PATCH 1/4] iio: dht11: Add locking

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Date:	Sun, 14 Dec 2014 13:31:19 +0100
From:	Hartmut Knaack <knaack.h@....de>
To:	Richard Weinberger <richard@....at>, jic23@...nel.org
CC:	harald@...ib.org, lars@...afoo.de, pmeerw@...erw.net,
	sanjeev_sharma@...tor.com, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] iio: dht11: Add locking

Richard Weinberger schrieb am 03.12.2014 um 00:32:
> Make sure that the read function is not interrupted...
There is already a mutex iio_dev->info_exist_lock used to serialize
iio_channel_read(), which in turn accesses _read_raw(). See [1].

[1]http://lxr.free-electrons.com/ident?i=iio_channel_read
> 
> Signed-off-by: Richard Weinberger <richard@....at>
> ---
>  drivers/iio/humidity/dht11.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/iio/humidity/dht11.c b/drivers/iio/humidity/dht11.c
> index d8771f5..168ebc4 100644
> --- a/drivers/iio/humidity/dht11.c
> +++ b/drivers/iio/humidity/dht11.c
> @@ -29,6 +29,7 @@
>  #include <linux/wait.h>
>  #include <linux/bitops.h>
>  #include <linux/completion.h>
> +#include <linux/mutex.h>
>  #include <linux/delay.h>
>  #include <linux/gpio.h>
>  #include <linux/of_gpio.h>
> @@ -57,6 +58,7 @@ struct dht11 {
>  	int				irq;
>  
>  	struct completion		completion;
> +	struct mutex			lock;
>  
>  	s64				timestamp;
>  	int				temperature;
> @@ -145,6 +147,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
>  	struct dht11 *dht11 = iio_priv(iio_dev);
>  	int ret;
>  
> +	mutex_lock(&dht11->lock);
>  	if (dht11->timestamp + DHT11_DATA_VALID_TIME < iio_get_time_ns()) {
>  		reinit_completion(&dht11->completion);
>  
> @@ -185,6 +188,7 @@ static int dht11_read_raw(struct iio_dev *iio_dev,
>  		ret = -EINVAL;
>  err:
>  	dht11->num_edges = -1;
> +	mutex_unlock(&dht11->lock);
>  	return ret;
>  }
>  
> @@ -268,6 +272,7 @@ static int dht11_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, iio);
>  
>  	init_completion(&dht11->completion);
> +	mutex_init(&dht11->lock);
>  	iio->name = pdev->name;
>  	iio->dev.parent = &pdev->dev;
>  	iio->info = &dht11_iio_info;
> 

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