linux-kernel - Re: [PATCH v5 13/18] iio: expose iio_device_set

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Date:   Sat, 16 Nov 2019 11:42:08 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Gwendal Grignou <gwendal@...omium.org>
Cc:     dmitry.torokhov@...il.com, groeck@...omium.org,
        briannorris@...omium.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, lee.jones@...aro.org, bleung@...omium.org,
        enric.balletbo@...labora.com, dianders@...omium.org,
        fabien.lahoudere@...labora.com, linux-kernel@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH v5 13/18] iio: expose iio_device_set_clock

On Fri, 15 Nov 2019 01:34:07 -0800
Gwendal Grignou <gwendal@...omium.org> wrote:

> Some IIO devices may want to override the default (realtime) to another
> clock source by default.
> It can beneficial when timestamps coming from the hardware or underlying
> drivers are already in that format.
> It can always be overridden by attribute current_timestamp_clock.
> 
> Signed-off-by: Gwendal Grignou <gwendal@...omium.org>
Definitely a step in the right direction.  We may want to also
consider a 'lock' on the value to prevent userspace overriding it, or
to perhaps limit the available choices.

For now though this lets you move forwards

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

> ---
>  drivers/iio/industrialio-core.c | 8 +++++++-
>  include/linux/iio/iio.h         | 2 ++
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index a46cdf2d8833..92815bdc14ee 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -188,7 +188,12 @@ ssize_t iio_read_const_attr(struct device *dev,
>  }
>  EXPORT_SYMBOL(iio_read_const_attr);
>  
> -static int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
> +/**
> + * iio_device_set_clock() - Set current timestamping clock for the device
> + * @indio_dev: IIO device structure containing the device
> + * @clock_id: timestamping clock posix identifier to set.
> + */
> +int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
>  {
>  	int ret;
>  	const struct iio_event_interface *ev_int = indio_dev->event_interface;
> @@ -206,6 +211,7 @@ static int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL(iio_device_set_clock);
>  
>  /**
>   * iio_get_time_ns() - utility function to get a time stamp for events etc
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 862ce0019eba..b18f34a8901f 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -627,6 +627,8 @@ static inline clockid_t iio_device_get_clock(const struct iio_dev *indio_dev)
>  	return indio_dev->clock_id;
>  }
>  
> +int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id);
> +
>  /**
>   * dev_to_iio_dev() - Get IIO device struct from a device struct
>   * @dev: 		The device embedded in the IIO device