On 23/03/17 17:36, Narcisa Ana Maria Vasile wrote:
> This device operates in DIRECT_MODE and BUFFER_HARDWARE mode.
> Replace usages of iio_dev->mlock with iio_device_{claim|release}_direct_mode()
> helper functions to guarantee DIRECT mode and consequently protect
> BUFFER mode too.
>
> Add and use a device private lock to protect against conflicting access of the
> state data.
> This helps with IIO subsystem 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.
>
> Remove lock from ad5933_work() because buffer mode should be enabled
> when we reach this, and claiming DIRECT mode in all the other places
> should protect it.
Well presented. I was wondering about the logic behind that...
>
> Signed-off-by: Narcisa Ana Maria Vasile <narcisaanamaria12@xxxxxxxxx>
This is certainly a fiddly one so I'd like some more eyes on it.
Lars - could you take a look? (he gets all the analog devices stuff ;)
> ---
> drivers/staging/iio/impedance-analyzer/ad5933.c | 50 ++++++++++++++-----------
> 1 file changed, 28 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/staging/iio/impedance-analyzer/ad5933.c b/drivers/staging/iio/impedance-analyzer/ad5933.c
> index 297665d..3d539ee 100644
> --- a/drivers/staging/iio/impedance-analyzer/ad5933.c
> +++ b/drivers/staging/iio/impedance-analyzer/ad5933.c
> @@ -98,6 +98,7 @@ struct ad5933_state {
> struct i2c_client *client;
> struct regulator *reg;
> struct delayed_work work;
> + struct mutex lock; /* Protect sensor state */
> unsigned long mclk_hz;
> unsigned char ctrl_hb;
> unsigned char ctrl_lb;
> @@ -306,9 +307,11 @@ static ssize_t ad5933_show_frequency(struct device *dev,
> u8 d8[4];
> } dat;
>
> - mutex_lock(&indio_dev->mlock);
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret)
> + return ret;
> ret = ad5933_i2c_read(st->client, this_attr->address, 3, &dat.d8[1]);
> - mutex_unlock(&indio_dev->mlock);
> + iio_device_release_direct_mode(indio_dev);
> if (ret < 0)
> return ret;
>
> @@ -338,9 +341,11 @@ static ssize_t ad5933_store_frequency(struct device *dev,
> if (val > AD5933_MAX_OUTPUT_FREQ_Hz)
> return -EINVAL;
>
> - mutex_lock(&indio_dev->mlock);
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret)
> + return ret;
> ret = ad5933_set_freq(st, this_attr->address, val);
This is the one case that standas out where we aren't taking the new lock..
It is setting a few internal state variables (st->freq_start and st->freq_inc)
but this is safe because those aren't actually read anywhere..
Presumably they were going to be cached, but the original author decided
against at some point later...
> - mutex_unlock(&indio_dev->mlock);
> + iio_device_release_direct_mode(indio_dev);
>
> return ret ? ret : len;
> }
> @@ -364,7 +369,7 @@ static ssize_t ad5933_show(struct device *dev,
> struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> int ret = 0, len = 0;
>
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&st->lock);
> switch ((u32)this_attr->address) {
> case AD5933_OUT_RANGE:
> len = sprintf(buf, "%u\n",
> @@ -393,7 +398,7 @@ static ssize_t ad5933_show(struct device *dev,
> ret = -EINVAL;
> }
>
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
> return ret ? ret : len;
> }
>
> @@ -415,7 +420,10 @@ static ssize_t ad5933_store(struct device *dev,
> return ret;
> }
>
> - mutex_lock(&indio_dev->mlock);
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret)
> + return ret;
> + mutex_lock(&st->lock);
> switch ((u32)this_attr->address) {
> case AD5933_OUT_RANGE:
> ret = -EINVAL;
> @@ -465,7 +473,8 @@ static ssize_t ad5933_store(struct device *dev,
> ret = -EINVAL;
> }
>
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->lock);
> + iio_device_release_direct_mode(indio_dev);
> return ret ? ret : len;
> }
>
> @@ -532,11 +541,9 @@ static int ad5933_read_raw(struct iio_dev *indio_dev,
>
> switch (m) {
> case IIO_CHAN_INFO_RAW:
> - mutex_lock(&indio_dev->mlock);
> - if (iio_buffer_enabled(indio_dev)) {
> - ret = -EBUSY;
> - goto out;
> - }
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret)
> + return ret;
> ret = ad5933_cmd(st, AD5933_CTRL_MEASURE_TEMP);
> if (ret < 0)
> goto out;
> @@ -549,7 +556,7 @@ static int ad5933_read_raw(struct iio_dev *indio_dev,
> 2, (u8 *)&dat);
> if (ret < 0)
> goto out;
> - mutex_unlock(&indio_dev->mlock);
> + iio_device_release_direct_mode(indio_dev);
> *val = sign_extend32(be16_to_cpu(dat), 13);
>
> return IIO_VAL_INT;
> @@ -561,7 +568,7 @@ static int ad5933_read_raw(struct iio_dev *indio_dev,
>
> return -EINVAL;
> out:
> - mutex_unlock(&indio_dev->mlock);
> + iio_device_release_direct_mode(indio_dev);
> return ret;
> }
>
> @@ -657,18 +664,17 @@ static void ad5933_work(struct work_struct *work)
> unsigned char status;
> int ret;
>
> - mutex_lock(&indio_dev->mlock);
> if (st->state == AD5933_CTRL_INIT_START_FREQ) {
> /* start sweep */
> ad5933_cmd(st, AD5933_CTRL_START_SWEEP);
> st->state = AD5933_CTRL_START_SWEEP;
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> - goto out;
> + return;
> }
>
> ret = ad5933_i2c_read(st->client, AD5933_REG_STATUS, 1, &status);
> if (ret)
> - goto out;
> + return;
>
> if (status & AD5933_STAT_DATA_VALID) {
> int scan_count = bitmap_weight(indio_dev->active_scan_mask,
> @@ -678,7 +684,7 @@ static void ad5933_work(struct work_struct *work)
> AD5933_REG_REAL_DATA : AD5933_REG_IMAG_DATA,
> scan_count * 2, (u8 *)buf);
> if (ret)
> - goto out;
> + return;
>
> if (scan_count == 2) {
> val[0] = be16_to_cpu(buf[0]);
> @@ -690,7 +696,7 @@ static void ad5933_work(struct work_struct *work)
> } else {
> /* no data available - try again later */
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> - goto out;
> + return;
> }
>
> if (status & AD5933_STAT_SWEEP_DONE) {
> @@ -703,8 +709,6 @@ static void ad5933_work(struct work_struct *work)
> ad5933_cmd(st, AD5933_CTRL_INC_FREQ);
> schedule_delayed_work(&st->work, st->poll_time_jiffies);
> }
> -out:
> - mutex_unlock(&indio_dev->mlock);
> }
>
> static int ad5933_probe(struct i2c_client *client,
> @@ -723,6 +727,8 @@ static int ad5933_probe(struct i2c_client *client,
> i2c_set_clientdata(client, indio_dev);
> st->client = client;
>
> + mutex_init(&st->lock);
> +
> if (!pdata)
> pdata = &ad5933_default_pdata;
>
>
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