linux-kernel - [PATCH v2 1/5] Documentation: ABI: add oversampling frequency in sysfs-bus-iio

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Message-ID: <20250422-iio-driver-ad4052-v2-1-638af47e9eb3@analog.com>
Date: Tue, 22 Apr 2025 13:34:46 +0200
From: Jorge Marques <jorge.marques@...log.com>
To: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>, Jonathan Corbet <corbet@....net>,
        David Lechner
	<dlechner@...libre.com>,
        Nuno Sá <nuno.sa@...log.com>,
        "Andy
 Shevchenko" <andy@...nel.org>,
        Uwe Kleine-König
	<ukleinek@...nel.org>
CC: <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>, Jorge Marques <jorge.marques@...log.com>
Subject: [PATCH v2 1/5] Documentation: ABI: add oversampling frequency in
 sysfs-bus-iio

Some devices have an internal clock used to space out the conversion
trigger for the oversampling filter,
Consider an ADC with conversion and data ready pins topology:

  Sampling trigger |       |       |       |       |
  ADC conversion   ++++    ++++    ++++    ++++    ++++
  ADC data ready      *       *       *       *       *

With the oversampling frequency, conversions are spaced:

  Sampling trigger |       |       |       |       |
  ADC conversion   + + + + + + + + + + + + + + + + + + + +
  ADC data ready         *       *       *       *       *

In some devices and ranges, this internal clock can be used to evenly
space the conversions between the sampling edge.
In other devices the oversampling frequency is fixed or is computed
based on the sampling frequency parameter, and the parameter is
read only.

Devices with this feature are max1363, ad7606, ad799x, and ad4052.
The max1363 driver included the events/sampling_frequency in
commit 168c9d95a940 ("iio:adc:max1363 move from staging.")
and ad799x in
commit ba1d79613df3 ("staging:iio:ad799x: Use event spec for threshold
hysteresis")
but went undocumented so far.

Signed-off-by: Jorge Marques <jorge.marques@...log.com>
---
 Documentation/ABI/testing/sysfs-bus-iio | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 33c09c4ac60a4feec82308461643134f5ba84b66..129061befb21b82a51142a01a94d96fcf1b60072 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -139,6 +139,23 @@ Contact:	linux-iio@...r.kernel.org
 Description:
 		Hardware dependent values supported by the oversampling filter.
 
+What:		/sys/bus/iio/devices/iio:deviceX/oversampling_frequency
+KernelVersion:	6.15
+Contact:	linux-iio@...r.kernel.org
+Description:
+		Some devices have internal clocks for oversampling.
+		Sets the resulting frequency in Hz to trigger a conversion used by
+		the oversampling filter.
+		If the device has a fixed internal clock or is computed based on
+		the sampling frequency parameter, the parameter is read only.
+
+What:		/sys/bus/iio/devices/iio:deviceX/oversampling_frequency_available
+KernelVersion:	6.15
+Contact:	linux-iio@...r.kernel.org
+Description:
+		Hardware dependent values supported by the oversampling
+		frequency.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_raw

-- 
2.49.0