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

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Date:	Sun, 14 Dec 2014 15:06:09 +0100
From:	Richard Weinberger <richard@....at>
To:	Hartmut Knaack <knaack.h@....de>, 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

Am 14.12.2014 um 13:31 schrieb Hartmut Knaack:
> 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

This is only for the in-kernel API and not for sysfs access.
I.e. if you access via sysfs it is not protected.

Thanks,
//richard

>> 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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