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SubjectRe: [PATCH 07/14] iio: triggers: on pollfunc attach, complete iio_dev if NULL
On Fri, 22 Dec 2017 17:07:14 +0200
Eugen Hristev <eugen.hristev@microchip.com> wrote:

> When attaching a pollfunc to a trigger, if the pollfunc does not
> have an associated iio_dev pointer, just use the private data
> iio_dev pointer from the trigger to fill in the poll func required
> iio_dev reference.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>

I'm yet to be convinced this is necessary rather than using a callback
buffer. It's also decidedly unsafe as there is no particular reason
in general to assume the private data is an iio_dev.

> ---
> drivers/iio/industrialio-trigger.c | 9 +++++++++
> include/linux/iio/trigger_consumer.h | 2 ++
> 2 files changed, 11 insertions(+)
>
> diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
> index 8565c92..ab180bd 100644
> --- a/drivers/iio/industrialio-trigger.c
> +++ b/drivers/iio/industrialio-trigger.c
> @@ -272,6 +272,15 @@ int iio_trigger_attach_poll_func(struct iio_trigger *trig,
> bool notinuse
> = bitmap_empty(trig->pool, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
>
> + /*
> + * If we did not get a iio_dev in the poll func, attempt to
> + * obtain the trigger's owner's device struct
> + */
> + if (!pf->indio_dev)
> + pf->indio_dev = iio_trigger_get_drvdata(trig);

That isn't always valid. Triggers don't always have a iio_dev associated
with them at all.
> + if (!pf->indio_dev)
> + return -EINVAL;
> +
> /* Prevent the module from being removed whilst attached to a trigger */
> __module_get(pf->indio_dev->driver_module);
>
> diff --git a/include/linux/iio/trigger_consumer.h b/include/linux/iio/trigger_consumer.h
> index aeefcdb..36e2a02 100644
> --- a/include/linux/iio/trigger_consumer.h
> +++ b/include/linux/iio/trigger_consumer.h
> @@ -63,6 +63,8 @@ int iio_triggered_buffer_predisable(struct iio_dev *indio_dev);
> /*
> * Two functions for the uncommon case when we need to attach or detach
> * a specific pollfunc to and from a trigger
> + * If the pollfunc has a NULL iio_dev pointer, it will be filled from the
> + * trigger struct.
> */
> int iio_trigger_attach_poll_func(struct iio_trigger *trig,
> struct iio_poll_func *pf);

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