[Linux-stm32] [PATCH 1/3] iio: adc: stm32-adc: warn if dt uses legacy channel config

[Fabrice Gasnier]

On 3/27/23 10:34, Sean Nyekjaer wrote:
> Since nearly all stm32 dt's are using the legacy adc channel config,
> we should warn users about using it.
> 
> Signed-off-by: Sean Nyekjaer <sean at geanix.com>
> ---
>  drivers/iio/adc/stm32-adc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 1aadb2ad2cab..d8e755d0cc52 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1993,6 +1993,8 @@ static int stm32_adc_get_legacy_chan_count(struct iio_dev *indio_dev, struct stm
>  	const struct stm32_adc_info *adc_info = adc->cfg->adc_info;
>  	int num_channels = 0, ret;
>  
> +	dev_warn(&indio_dev->dev, "using legacy channel config\n");
> +

Hi Sean,

I'd recommend to avoid adding a dev_warn() on a per driver basis, for
depreacted DT properties. Still I'm not sure if there's some policy in
this area.

IMHO, deprecated properties should be checked by using dt tools
(dt_binding_check / dtbs_check or other mean?). But I have no idea if
this is going to report warnings and when. Purpose would be to avoid
introducing no dts files with these. As commented by Olivier on Patch 3,
we've some downstream patches to adopt the generic bindings (not
upstream 'yet').

Another downside is regarding backward compatibility. In case an old dtb
is used to boot the kernel, as long as there's no functionality loss,
I'd advise not to use any warning here. That's a valid use of an old dt.

In all case, thanks for pointing issues (e.g. Patch 2 & 3), regarding
this patch, I'd nack adding this warning. Please drop this change if you
re-submit or turn this into a dev_dbg().

Best Regards,
Fabrice

>  	ret = device_property_count_u32(dev, "st,adc-channels");
>  	if (ret > adc_info->max_channels) {
>  		dev_err(&indio_dev->dev, "Bad st,adc-channels?\n");