linux-kernel - [PATCH v7 2/5] ABI: sysfs-bus-iio: Disambiguate usage for filter

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Message-Id: <20250825-mcp9600-iir-v7-2-2ba676a52589@kernel.org>
Date: Mon, 25 Aug 2025 20:10:04 -0400
From: Ben Collins <bcollins@...nel.org>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, 
 Antoniu Miclaus <antoniu.miclaus@...log.com>, 
 Lars-Peter Clausen <lars@...afoo.de>, 
 Michael Hennerich <Michael.Hennerich@...log.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Ben Collins <bcollins@...nel.org>
Subject: [PATCH v7 2/5] ABI: sysfs-bus-iio: Disambiguate usage for
 filter_type "none"

When a filter_type is "none", there really is no useful information that
can be presented from sampling and frequency attributes.

This is especially true when the driver supports more than one
filter_type, since the information would be ambiguous.

Suggest returning IIO_VAL_EMPTY for this case.

Signed-off-by: Ben Collins <bcollins@...nel.org>
---
 Documentation/ABI/testing/sysfs-bus-iio | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 7e31b8cd49b32ea5b58bd99afc2e8105314d7a39..df42a4040530ee96096b998bebc8a08b4fb2d78f 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -2276,7 +2276,11 @@ Description:
 		Reading returns a list with the possible filter modes. Options
 		for the attribute:
 
-		* "none" - Filter is disabled/bypassed.
+		* "none" - Filter is disabled/bypassed. When set in the
+		  filter_type attribute, a driver should return IIO_VAL_EMPTY
+		  when reading sampling and frequency related attributes of
+		  this filter, and return -EINVAL when trying to write these
+		  attributes.
 		* "sinc1" - The digital sinc1 filter. Fast 1st
 		  conversion time. Poor noise performance.
 		* "sinc3" - The digital sinc3 filter. Moderate 1st

-- 
2.39.5