The only driver exporting filter_type_available attribute is ad7779 and it
only supports sinc3 and sinc5 filters. Remove options that are not
presented through filter_type_available attribute.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
Maybe this is not worth it (or desirable?) since the options may come back in
the future if new drivers happen to need them.

 Documentation/ABI/testing/sysfs-bus-iio | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 1ddf3d7dd2b3..946c519f8687 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -2280,24 +2280,13 @@ What:		/sys/bus/iio/devices/iio:deviceX/filter_type_available
 KernelVersion:	6.1
 Contact:	linux-iio@vger.kernel.org
 Description:
-		Reading returns a list with the possible filter modes. Options
-		for the attribute:
+		Lists all available filter types. Possible options for the
+		attribute:
 
-		* "sinc3" - The digital sinc3 filter. Moderate 1st
-		  conversion time. Good noise performance.
-		* "sinc4" - Sinc 4. Excellent noise performance. Long
-		  1st conversion time.
+		* "sinc3" - The digital sinc3 filter. Moderate 1st conversion
+		  time. Good noise performance.
 		* "sinc5" - The digital sinc5 filter. Excellent noise
-		  performance
-		* "sinc4+sinc1" - Sinc4 + averaging by 8. Low 1st conversion
-		  time.
-		* "sinc3+rej60" - Sinc3 + 60Hz rejection.
-		* "sinc3+sinc1" - Sinc3 + averaging by 8. Low 1st conversion
-		  time.
-		* "sinc3+pf1" - Sinc3 + device specific Post Filter 1.
-		* "sinc3+pf2" - Sinc3 + device specific Post Filter 2.
-		* "sinc3+pf3" - Sinc3 + device specific Post Filter 3.
-		* "sinc3+pf4" - Sinc3 + device specific Post Filter 4.
+		  performance.
 
 What:		/sys/bus/iio/devices/iio:deviceX/filter_type
 KernelVersion:	6.1
-- 
2.45.2

On 1/7/25 9:13 AM, Marcelo Schmitt wrote:
> The only driver exporting filter_type_available attribute is ad7779 and it
> only supports sinc3 and sinc5 filters. Remove options that are not
> presented through filter_type_available attribute.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> ---
> Maybe this is not worth it (or desirable?) since the options may come back in
> the future if new drivers happen to need them.

I would be tempted to add filter_type{,_available} attributes to the ad4130
driver that mirrors the existing filter_mode{,_available} attributes. We can't
remove filter_mode since that would break things, but having filter_type in
addition to that would mean than userspace tools could standardize on
filter_type and not have to make a special exception for the different naming
on ad4130.

Then we wouldn't need to delete the extra items here and we wouldn't have to
repeat the docs for sysfs-bus-iio-adc-ad4130. Those docs can just have the
deprecation paragraph and mention that it returns values identical to the
filter_type attributes for backwards compatibility.

On Tue, 7 Jan 2025 11:53:44 -0600
David Lechner <dlechner@baylibre.com> wrote:

> On 1/7/25 9:13 AM, Marcelo Schmitt wrote:
> > The only driver exporting filter_type_available attribute is ad7779 and it
> > only supports sinc3 and sinc5 filters. Remove options that are not
> > presented through filter_type_available attribute.
> > 
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> > ---
> > Maybe this is not worth it (or desirable?) since the options may come back in
> > the future if new drivers happen to need them.  
> 
> I would be tempted to add filter_type{,_available} attributes to the ad4130
> driver that mirrors the existing filter_mode{,_available} attributes. We can't
> remove filter_mode since that would break things, but having filter_type in
> addition to that would mean than userspace tools could standardize on
> filter_type and not have to make a special exception for the different naming
> on ad4130.
> 
> Then we wouldn't need to delete the extra items here and we wouldn't have to
> repeat the docs for sysfs-bus-iio-adc-ad4130. Those docs can just have the
> deprecation paragraph and mention that it returns values identical to the
> filter_type attributes for backwards compatibility.

Good idea.  Given we always allow any attribute to change any other, having
duplicates for ABI backwards compatibility is fine.

Thanks,

Jonathan