Re: [RFC PATCH] iio: __iio_update_buffers: Update mode before preenable/after postdisable

From: Eugen.Hristev
Date: Thu Apr 30 2020 - 04:42:44 EST


On 30.04.2020 11:24, Alexandru Ardelean wrote:
> From: Lars-Peter Clausen <lars@xxxxxxxxxx>
>
> It is clear that we transition to INDIO_DIRECT_MODE when disabling the
> buffer(s) and it is also clear that we transition from INDIO_DIRECT_MODE
> when enabling the buffer(s). So leaving the currentmode field
> INDIO_DIRECT_MODE until after the preenable() callback and updating it to
> INDIO_DIRECT_MODE before the postdisable() callback doesn't add additional
> value. On the other hand some drivers will need to perform different
> actions depending on which mode the device is going to operate in/was
> operating in.
>
> Moving the update of currentmode before preenable() and after postdisable()
> enables us to have drivers which perform mode dependent actions in those
> callbacks.
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
> ---
>
> This patch is also a V2 of this older patch from a while ago:
> https://lore.kernel.org/linux-iio/1431525891-19285-5-git-send-email-lars@xxxxxxxxxx/
>
> However, in this recent context, it comes to fix this:
> https://lore.kernel.org/linux-iio/b9ab676489de3575984dac5610fcf05fd8742a38.camel@xxxxxxxxxx/T/#mc09284c8f79250b92a52fd5b8d1f541d1c02c0c0
>
> At this point, I don't have a clear idea if this approach is good or
> not; since the motivation is to fix the at91 adc.
> Hence the RFC.
>
> Some excerpt from the AT91 discussion:
> -------------------------------------------------------------------
> I decided to do a bit of shell magic for this:
>
> get_files() {
> git grep -w iio_buffer_setup_ops | grep drivers | cut -d: -f1 | sort | uniq
> }
>
> for file in $(get_files) ; do
> if grep -q currentmode $file ; then
> echo $file
> fi
> done
>
> It finds 4 drivers.
> Though, `get_files()` will return 56 files.
>
> drivers/iio/accel/bmc150-accel-core.c
> drivers/iio/adc/at91-sama5d2_adc.c
> drivers/iio/adc/stm32-dfsdm-adc.c
> drivers/iio/magnetometer/rm3100-core.c
>
> The rm3100 driver doesn't do any checks in the setup_ops for 'currentmode' as
> far as I could see.
>
> So, Lars' patch could work nicely to fix this current case and not break others.
>
> Semantically though, it would sound nicer to have a 'nextmode' parameter
> somewhere; maybe on the setup_ops(indio_dev, nextmode)?
> Though, only those 3 drivers would really ever use it; so doing it like that
> sounds like overkill.
>
> So, we're left with Lars' patch or we could add an 'indio_dev->nextmode' field,
> that may be used in just these 3 drivers [which again: sounds overkill at this
> point in time].
>
> Alternatively, this 'indio_dev->currentmode' could be removed from all these 3
> drivers somehow. But that needs testing and a thorough understanding of all 3
> drivers and what they're doing, to do properly.
> -------------------------------------------------------------------

Hi Alex,

Thanks for finding this. I will test this with the at91-sama5d2_adc
driver on Jonathan's testing branch. I will let you know of the results.

Eugen

>
> drivers/iio/industrialio-buffer.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 30af8af8f312..efcc44b62946 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -989,6 +989,7 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
> indio_dev->active_scan_mask = config->scan_mask;
> indio_dev->scan_timestamp = config->scan_timestamp;
> indio_dev->scan_bytes = config->scan_bytes;
> + indio_dev->currentmode = config->mode;
>
> iio_update_demux(indio_dev);
>
> @@ -1024,8 +1025,6 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
> goto err_disable_buffers;
> }
>
> - indio_dev->currentmode = config->mode;
> -
> if (indio_dev->setup_ops->postenable) {
> ret = indio_dev->setup_ops->postenable(indio_dev);
> if (ret) {
> @@ -1042,10 +1041,10 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
> buffer_list)
> iio_buffer_disable(buffer, indio_dev);
> err_run_postdisable:
> - indio_dev->currentmode = INDIO_DIRECT_MODE;
> if (indio_dev->setup_ops->postdisable)
> indio_dev->setup_ops->postdisable(indio_dev);
> err_undo_config:
> + indio_dev->currentmode = INDIO_DIRECT_MODE;
> indio_dev->active_scan_mask = NULL;
>
> return ret;
> @@ -1080,8 +1079,6 @@ static int iio_disable_buffers(struct iio_dev *indio_dev)
> ret = ret2;
> }
>
> - indio_dev->currentmode = INDIO_DIRECT_MODE;
> -
> if (indio_dev->setup_ops->postdisable) {
> ret2 = indio_dev->setup_ops->postdisable(indio_dev);
> if (ret2 && !ret)
> @@ -1090,6 +1087,7 @@ static int iio_disable_buffers(struct iio_dev *indio_dev)
>
> iio_free_scan_mask(indio_dev, indio_dev->active_scan_mask);
> indio_dev->active_scan_mask = NULL;
> + indio_dev->currentmode = INDIO_DIRECT_MODE;
>
> return ret;
> }
> --
> 2.17.1
>