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.
There are other read/write functions for example,
ade7753_spi_{read/write}_reg_8 that use the mutex as well. Should a
variant of these functions be introduced as well? Also, how does one
go about implementing RMW inside a protected section.
>
> 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.
Am I right in understanding that we want to introduce mutex lock for
writes in other drivers as well?
Thanks,
Gargi
>
> > **/
> > 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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