Re: [PATCH v8] staging: adis16060: Remove iio_dev mlock and refactor code

[Jonathan Cameron <jic23@kernel.org>]

On 22 March 2017 19:22:20 GMT+00:00, Jonathan Cameron <jic23@kernel.org> wrote:
>On 22/03/17 16:20, simran singhal wrote:
>> The IIO subsystem is redefining iio_dev->mlock to be used by
>> the IIO core only for protecting device operating mode changes.
>> ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes.
>> 
>> In this driver, mlock was being used to protect hardware state
>changes.
>> 
>> In the driver, buf_lock protects both the adis16060_spi_write() and
>> adis16060_spi_read() functions and both are always called in
>> pair. First write, then read. Refactor the code to have
>> one single function adis16060_spi_write_than_read() and remove
>> the use of mlock as adis16060_read_raw() does not require an
>> iio_dev->mlock for reads.
>I'll slightly modify this description.  The key thing is
>that after the above change to have a unified read then write
>there is no longer any need for mlock to protect these
>read, update, write cycles.
>> 
>> Signed-off-by: simran singhal <singhalsimran0@gmail.com>
>Applied to the togreg branch of iio.git and pushed out as testing
>for the autobuilders to play with it.
>
>I slightly modified the title as well. It's useful to be a little
>more specific than staging, so I added iio: after that.

Another example of how the tests that 0day is doing are way better than my tired eyes at the end of a day...
>
>Thanks,
>
>Jonathan
>> ---
>> 
>>  v8:
>>    -change subject
>>    -change commit message
>>  v7:
>>    -Change subject
>>    -Remove lock from read_raw instead from
>>     function adis16060_spi_write_than_read().
>>  v6:
>>    -Change commit message
>>    -Remove nested lock
>>  v5:
>>    -Rename val in adis16060_spi_write_than_read() to conf.
>>    -Rename val2 in adis16060_spi_write_than_read() to val.
>>    -Corrected Checkpatch issues.
>>    -Removed goto from adis16060_read_raw().
>>  v4:
>>    -Refactored code
>>    -change commit subject
>>    -change commit message
>>  v3:
>>    -Removed new lock to reuse the existing lock
>>  v2:
>>    -Fixed compilation error
>> 
>>  drivers/staging/iio/gyro/adis16060_core.c | 33
>++++++++-----------------------
>>  1 file changed, 8 insertions(+), 25 deletions(-)
>> 
>> diff --git a/drivers/staging/iio/gyro/adis16060_core.c
>b/drivers/staging/iio/gyro/adis16060_core.c
>> index c9d46e7..e96fce5 100644
>> --- a/drivers/staging/iio/gyro/adis16060_core.c
>> +++ b/drivers/staging/iio/gyro/adis16060_core.c
>> @@ -40,25 +40,18 @@ struct adis16060_state {
>>  
>>  static struct iio_dev *adis16060_iio_dev;
>>  
>> -static int adis16060_spi_write(struct iio_dev *indio_dev, u8 val)
>> +static int adis16060_spi_write_than_read(struct iio_dev *indio_dev,
>> +					 u8 conf, u16 *val)
>>  {
>>  	int ret;
>>  	struct adis16060_state *st = iio_priv(indio_dev);
>>  
>>  	mutex_lock(&st->buf_lock);
>> -	st->buf[2] = val; /* The last 8 bits clocked in are latched */
>> +	st->buf[2] = conf; /* The last 8 bits clocked in are latched */
>>  	ret = spi_write(st->us_w, st->buf, 3);
>> -	mutex_unlock(&st->buf_lock);
>> -
>> -	return ret;
>> -}
>> -
>> -static int adis16060_spi_read(struct iio_dev *indio_dev, u16 *val)
>> -{
>> -	int ret;
>> -	struct adis16060_state *st = iio_priv(indio_dev);
>>  
>> -	mutex_lock(&st->buf_lock);
>> +	if (ret < 0)
Not unlocking buf_lock in this path.  I will fix up later....

Jonathan
>> +		return ret;
>>  
>>  	ret = spi_read(st->us_r, st->buf, 3);
>>  
>> @@ -86,17 +79,11 @@ static int adis16060_read_raw(struct iio_dev
>*indio_dev,
>>  
>>  	switch (mask) {
>>  	case IIO_CHAN_INFO_RAW:
>> -		/* Take the iio_dev status lock */
>> -		mutex_lock(&indio_dev->mlock);
>> -		ret = adis16060_spi_write(indio_dev, chan->address);
>> +		ret = adis16060_spi_write_than_read(indio_dev,
>> +						    chan->address, &tval);
>>  		if (ret < 0)
>> -			goto out_unlock;
>> +			return ret;
>>  
>> -		ret = adis16060_spi_read(indio_dev, &tval);
>> -		if (ret < 0)
>> -			goto out_unlock;
>> -
>> -		mutex_unlock(&indio_dev->mlock);
>>  		*val = tval;
>>  		return IIO_VAL_INT;
>>  	case IIO_CHAN_INFO_OFFSET:
>> @@ -110,10 +97,6 @@ static int adis16060_read_raw(struct iio_dev
>*indio_dev,
>>  	}
>>  
>>  	return -EINVAL;
>> -
>> -out_unlock:
>> -	mutex_unlock(&indio_dev->mlock);
>> -	return ret;
>>  }
>>  
>>  static const struct iio_info adis16060_info = {
>> 
>
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