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SubjectRe: [PATCH] iio: stm32-dac: Replace indio_dev->mlock with own device lock
On Thu, 14 May 2020 11:50:12 +0300
Sergiu Cuciurean <sergiu.cuciurean@analog.com> wrote:

> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock on the device's state structure.
>
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> ---
> drivers/iio/dac/stm32-dac.c | 12 ++++++++----
> 1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> index f22c1d9129b2..74b9474c8590 100644
> --- a/drivers/iio/dac/stm32-dac.c
> +++ b/drivers/iio/dac/stm32-dac.c
> @@ -26,9 +26,11 @@
> /**
> * struct stm32_dac - private data of DAC driver
> * @common: reference to DAC common data
> + * @lock: lock to protect the data buffer during regmap ops

In this particular case I'm not sure that's what mlock was being used for.
I think it's about avoiding races around checking if powered down and
actually doing it.


> */
> struct stm32_dac {
> struct stm32_dac_common *common;
> + struct mutex lock;
> };
>
> static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> @@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> int ret;
>
> /* already enabled / disabled ? */
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&dac->lock);
> ret = stm32_dac_is_enabled(indio_dev, ch);
> if (ret < 0 || enable == !!ret) {
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&dac->lock);
> return ret < 0 ? ret : 0;
> }
>
> @@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> ret = pm_runtime_get_sync(dev);
> if (ret < 0) {
> pm_runtime_put_noidle(dev);
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&dac->lock);
> return ret;
> }
> }
>
> ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&dac->lock);
> if (ret < 0) {
> dev_err(&indio_dev->dev, "%s failed\n", en ?
> "Enable" : "Disable");
> @@ -328,6 +330,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
> indio_dev->info = &stm32_dac_iio_info;
> indio_dev->modes = INDIO_DIRECT_MODE;
>
> + mutex_init(&dac->lock);
> +
> ret = stm32_dac_chan_of_init(indio_dev);
> if (ret < 0)
> return ret;

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