On Mon, 9 Mar 2020 00:11:06 +0530
Rohit Sarkar <rohitsarkar5398@xxxxxxxxx> wrote:
> Replace usage indio_dev's mlock with either local lock or
> iio_device_claim_direct_mode.
>
> Signed-off-by: Rohit Sarkar <rohitsarkar5398@xxxxxxxxx>
Nearly there. A few minor issues around handling failure to claim direct
mode (which will happen if the buffer is enabled).
Jonathan
> ---
> Changelog v4 -> v5
> Use local lock too at places where driver state needs to be protected.
>
> Changelog v3 -> v4
> * Fix indentation
>
> Changelog v2 -> v3
> * use iio_device_claim_direct when switching modes
> * replace mlock usage in max1363_write_event_config
>
> Changelog v1 -> v2
> * Fix indentation
>
> drivers/iio/adc/max1363.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
> index 5c2cc61b666e..856f523e7018 100644
> --- a/drivers/iio/adc/max1363.c
> +++ b/drivers/iio/adc/max1363.c
> @@ -150,6 +150,7 @@ struct max1363_chip_info {
> * @current_mode: the scan mode of this chip
> * @requestedmask: a valid requested set of channels
> * @reg: supply regulator
> + * @lock lock to ensure state is consistent
> * @monitor_on: whether monitor mode is enabled
> * @monitor_speed: parameter corresponding to device monitor speed setting
> * @mask_high: bitmask for enabled high thresholds
> @@ -169,6 +170,7 @@ struct max1363_state {
> const struct max1363_mode *current_mode;
> u32 requestedmask;
> struct regulator *reg;
> + struct mutex lock;
>
> /* Using monitor modes and buffer at the same time is
> currently not supported */
> @@ -364,7 +366,11 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> struct max1363_state *st = iio_priv(indio_dev);
> struct i2c_client *client = st->client;
>
> - mutex_lock(&indio_dev->mlock);
> + ret = iio_device_claim_direct_mode(indio_dev);
If this fails, no locks are held, so return directly here.
You don't want to call iio_device_release_direct_mode in that case.
General rule of thumb in kernel is that a function returning an error
should have no 'side effects' - it should be as if it never ran.
> + mutex_lock(&st->lock);
> +
> + if (ret < 0)
> + goto error_ret;
> /*
> * If monitor mode is enabled, the method for reading a single
> * channel will have to be rather different and has not yet
> @@ -372,7 +378,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> *
> * Also, cannot read directly if buffered capture enabled.
> */
> - if (st->monitor_on || iio_buffer_enabled(indio_dev)) {
> + if (st->monitor_on) {
> ret = -EBUSY;
> goto error_ret;
> }
> @@ -404,8 +410,10 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> data = rxbuf[0];
> }
> *val = data;
> +
> error_ret:
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
> + iio_device_release_direct_mode(indio_dev);
> return ret;
>
> }
> @@ -705,9 +713,9 @@ static ssize_t max1363_monitor_store_freq(struct device *dev,
> if (!found)
> return -EINVAL;
>
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&st->lock);
> st->monitor_speed = i;
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
>
> return 0;
> }
> @@ -810,12 +818,12 @@ static int max1363_read_event_config(struct iio_dev *indio_dev,
> int val;
> int number = chan->channel;
>
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&st->lock);
> if (dir == IIO_EV_DIR_FALLING)
> val = (1 << number) & st->mask_low;
> else
> val = (1 << number) & st->mask_high;
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
>
> return val;
> }
> @@ -962,7 +970,9 @@ static int max1363_write_event_config(struct iio_dev *indio_dev,
> u16 unifiedmask;
> int number = chan->channel;
>
> - mutex_lock(&indio_dev->mlock);
> + iio_device_claim_direct_mode(indio_dev);
You have to check the result claim_direct_mode. It will fail if we are in buffered
mode. If that happens just return -EBUSY and don't do anything else.
> + mutex_lock(&st->lock);
> +
> unifiedmask = st->mask_low | st->mask_high;
> if (dir == IIO_EV_DIR_FALLING) {
>
> @@ -989,7 +999,8 @@ static int max1363_write_event_config(struct iio_dev *indio_dev,
>
> max1363_monitor_mode_update(st, !!(st->mask_high | st->mask_low));
> error_ret:
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
> + iio_device_release_direct_mode(indio_dev);
>
> return ret;
> }
> @@ -1587,6 +1598,7 @@ static int max1363_probe(struct i2c_client *client,
>
> st = iio_priv(indio_dev);
>
> + mutex_init(&st->lock);
> st->reg = devm_regulator_get(&client->dev, "vcc");
> if (IS_ERR(st->reg)) {
> ret = PTR_ERR(st->reg);
