Re: [RFC PATCH 2/7] iio:ABI docs: Avoid repitition of triggerX/sampling_frequency

[Lars-Peter Clausen <lars@metafoo.de>]

On 1/17/21 4:38 PM, Jonathan Cameron wrote:
> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>
> The timer-stm32 provided a little more specific information than the main
> docs about the value of 0 corresponding to stopping sampling.  Given that
> this makes sense in general, move that statement over to the main docs
> and drop the version in sysfs-bus-iio-timer-stm32
>
> Fixes
> $ scripts/get_abi.pl validate
> /sys/bus/iio/devices/triggerX/sampling_frequency is defined 2 times:  ./Documentation/ABI/testing/sysfs-bus-iio-timer-stm32:92  ./Documentation/ABI/testing/sysfs-bus-iio:45
>
> Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
> Reported-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>   Documentation/ABI/testing/sysfs-bus-iio             | 2 ++
>   Documentation/ABI/testing/sysfs-bus-iio-timer-stm32 | 8 --------
>   2 files changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index d2dd9cc280f9..9b5ceb22363d 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -55,6 +55,8 @@ Description:
>   		direct access interfaces, it may be found in any of the
>   		relevant directories.  If it affects all of the above
>   		then it is to be found in the base device directory.
> +		Note a value 0 where supported, will correspond to sampling
> +		stopping.

Hm, I don't like this. 0 should be an invalid value for the standard 
ABI. Enabling/disabling of the trigger should be controlled by whether 
there are any active trigger consumers.

The stm32-timer-trigger implements a non-standard ABI and I think we 
need to document this explicitly. The driver does not have a set_state 
callback. So the frequency property is used to enable/disable the 
trigger, but as said above, for standard compliant triggers that should 
not be the case.