On Mon, Mar 13, 2017 at 5:30 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> On 03/12/2017 02:32 PM, 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. Replace it with a lock in the devices global data.
>>
>> Fix some coding style issues related to white space also.
>>
>> Signed-off-by: simran singhal <singhalsimran0@xxxxxxxxx>
>> ---
>> drivers/staging/iio/meter/ade7753.c | 14 ++++++++------
>> 1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/staging/iio/meter/ade7753.c b/drivers/staging/iio/meter/ade7753.c
>> index dfd8b71..ca99d82 100644
>> --- a/drivers/staging/iio/meter/ade7753.c
>> +++ b/drivers/staging/iio/meter/ade7753.c
>> @@ -81,12 +81,14 @@
>> * @tx: transmit buffer
>> * @rx: receive buffer
>> * @buf_lock: mutex to protect tx and rx
>> + * @lock: protect sensor state
>
> It might make sense to reuse the existing lock which currently protects the
> read/write functions. You can do this by introducing a variant of
> ade7753_spi_{read,write}_reg_16() that does not take a lock and use these to
> implement the read-modify-write cycle in a protected section.
>
The only instance I was able to find was drivers/iio/adc/vf610_adc.c
where read modify write cycles are present on the register
VF610_REG_ADC_CFG. I believe writel() & readl() is used for this
purpose.
In this case, we want to write to data to a device on the SPI bus. Can
we use writel() for this purpose?
> Looking through the driver there seem to be other places as well that do
> read-modify-write that should be protected by a lock, but currently are not.
> This might be a good task.
>
>> **/
>> struct ade7753_state {
>> - struct spi_device *us;
>> - struct mutex buf_lock;
>> - u8 tx[ADE7753_MAX_TX] ____cacheline_aligned;
>> - u8 rx[ADE7753_MAX_RX];
>> + struct spi_device *us;
>> + struct mutex buf_lock;
>> + struct mutex lock; /* protect sensor state */
>> + u8 tx[ADE7753_MAX_TX] ____cacheline_aligned;
>> + u8 rx[ADE7753_MAX_RX];
>> };
>>
>> static int ade7753_spi_write_reg_8(struct device *dev,
>> @@ -484,7 +486,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
>> if (!val)
>> return -EINVAL;
>>
>> - mutex_lock(&indio_dev->mlock);
>> + mutex_lock(&st->lock);
>>
>> t = 27900 / val;
>> if (t > 0)
>> @@ -505,7 +507,7 @@ static ssize_t ade7753_write_frequency(struct device *dev,
>> ret = ade7753_spi_write_reg_16(dev, ADE7753_MODE, reg);
>>
>> out:
>> - mutex_unlock(&indio_dev->mlock);
>> + mutex_unlock(&st->lock);
>>
>> return ret ? ret : len;
>> }
>>
>
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