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Tue, 07 Jul 2026 08:17:49 -0700 (PDT) From: Muchamad Coirul Anwar To: jic23@kernel.org, lars@metafoo.de Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, andi.shyti@kernel.org, wsa+renesas@sang-engineering.com, ojeda@kernel.org, dakr@kernel.org, igor.korotin@linux.dev, branstj@gmail.com, Muchamad Coirul Anwar Subject: [RFC PATCH v4 3/3] iio: position: add Rust driver for ams AS5600 Date: Tue, 7 Jul 2026 22:15:42 +0700 Message-ID: <20260707151542.91997-4-muchamadcoirulanwar@gmail.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20260707151542.91997-1-muchamadcoirulanwar@gmail.com> References: <20260707151542.91997-1-muchamadcoirulanwar@gmail.com> Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a Rust driver for the ams AS5600 12-bit magnetic rotary position sensor. The driver exposes in_angl_raw and in_angl_scale via the IIO sysfs interface. Features: - ARef for safe refcounted I2C client access - Mutex-serialized status + angle read sequence - Static channel spec (module-level const) - No magnet validation at probe (deferred to read_raw per IIO convention) - Error propagation via ? operator (no recovery state machine) The byte order for the AS5600's big-endian registers is handled via swap_bytes() in-driver. This is equivalent to C's i2c_smbus_read_word_swapped(). The long-term solution is regmap-rs where endianness is configured once at the transport level. Tested on BeagleBone Black (AM335x) with AS5600 on i2c-2 (0x36). Signed-off-by: Muchamad Coirul Anwar --- drivers/iio/position/Kconfig | 14 +++ drivers/iio/position/Makefile | 1 + drivers/iio/position/as5600.rs | 181 +++++++++++++++++++++++++++++++++ 3 files changed, 196 insertions(+) create mode 100644 drivers/iio/position/as5600.rs diff --git a/drivers/iio/position/Kconfig b/drivers/iio/position/Kconfig index 1576a6380b53..573d241676bf 100644 --- a/drivers/iio/position/Kconfig +++ b/drivers/iio/position/Kconfig @@ -6,6 +6,20 @@ menu "Linear and angular position sensors" +config AS5600 + tristate "ams AS5600 magnetic rotary position sensor" + depends on I2C && IIO && RUST + help + Say Y here to build support for the ams AS5600 12-bit + magnetic rotary position sensor with IIO channel support + (in_angl_raw and in_angl_scale). + + This is a Rust driver that exposes the 12-bit raw angle + and radian scale via the IIO subsystem. + + To compile this driver as a module, choose M here: the + module will be called as5600. + config IQS624_POS tristate "Azoteq IQS624/625 angular position sensors" depends on MFD_IQS62X || COMPILE_TEST diff --git a/drivers/iio/position/Makefile b/drivers/iio/position/Makefile index d70902f2979d..2d26f6d6ace3 100644 --- a/drivers/iio/position/Makefile +++ b/drivers/iio/position/Makefile @@ -4,5 +4,6 @@ # When adding new entries keep the list in alphabetical order +obj-$(CONFIG_AS5600) += as5600.o obj-$(CONFIG_HID_SENSOR_CUSTOM_INTEL_HINGE) += hid-sensor-custom-intel-hinge.o obj-$(CONFIG_IQS624_POS) += iqs624-pos.o diff --git a/drivers/iio/position/as5600.rs b/drivers/iio/position/as5600.rs new file mode 100644 index 000000000000..7445398c86b9 --- /dev/null +++ b/drivers/iio/position/as5600.rs @@ -0,0 +1,181 @@ +// SPDX-License-Identifier: GPL-2.0-only +// Copyright (C) 2026 Muchamad Coirul Anwar +//! Driver for ams AS5600 12-bit magnetic rotary position sensor. +//! +//! Datasheet: https://look.ams-osram.com/m/7059eac7531a86fd/original/AS5600-DS000365.pdf + +use kernel::{ + bindings::{ + iio_chan_info_enum_IIO_CHAN_INFO_RAW, + iio_chan_info_enum_IIO_CHAN_INFO_SCALE, + iio_chan_spec, + iio_chan_type_IIO_ANGL, // + }, + bits::{ + bit_u8, + genmask_u16, // + }, + device::Core, + error::code::{ + EINVAL, + ENODATA, // + }, + i2c::{ + DeviceId, + Driver, + I2cClient, + IdTable, // + }, + i2c_device_table, + iio::{ + Device, + IioDriver, + IioVal, + Registered, // + }, + io::Io, + module_i2c_driver, + of, + of_device_table, + prelude::*, // + sync::{ + aref::ARef, + new_mutex, + Mutex, // + }, +}; + +const AS5600_REG_STATUS: u8 = 0x0B; +const AS5600_REG_RAW_ANGLE_H: u8 = 0x0C; + +const AS5600_STATUS_MD: u8 = bit_u8(5); +const AS5600_RAW_ANGLE_MASK: u16 = genmask_u16(0..=11); + +module_i2c_driver! { + type: As5600, + name: "as5600", + authors: ["Muchamad Coirul Anwar"], + description: "I2C Driver for ams OSRAM AS5600 Magnetic Rotary Position Sensor", + license: "GPL", +} + +i2c_device_table!( + I2C_TABLE, + MODULE_I2C_TABLE, + ::IdInfo, + [(DeviceId::new(c"as5600"), ())] +); + +of_device_table!( + OF_TABLE, + MODULE_OF_TABLE, + ::IdInfo, + [(of::DeviceId::new(c"ams,as5600"), ())] +); + +struct As5600Channels([iio_chan_spec; 1]); + +// SAFETY: `iio_chan_spec` is a plain C struct (all fields are integers/pointers) +// with no interior mutability. The static is only read after initialization, +// making shared access safe. +unsafe impl Sync for As5600Channels {} + +static AS5600_CHANNELS: As5600Channels = As5600Channels({ + // SAFETY: `iio_chan_spec` is a repr(C) struct where all-zeroes is valid + // (integers default to 0, pointers to NULL). + let mut chan: iio_chan_spec = unsafe { core::mem::zeroed() }; + chan.type_ = iio_chan_type_IIO_ANGL; + // TODO: Use kernel::bits equivalent once bit_usize exists + chan.info_mask_separate = (1usize << iio_chan_info_enum_IIO_CHAN_INFO_RAW) + | (1usize << iio_chan_info_enum_IIO_CHAN_INFO_SCALE); + [chan] +}); + +#[pin_data] +struct As5600Priv { + #[pin] + io_lock: Mutex, +} + +struct As5600HwState { + client: ARef, +} + +impl IioDriver for As5600Priv { + fn read_raw(&self, _chan: *const iio_chan_spec, mask: isize) -> Result { + const INFO_RAW: isize = iio_chan_info_enum_IIO_CHAN_INFO_RAW as isize; + const INFO_SCALE: isize = iio_chan_info_enum_IIO_CHAN_INFO_SCALE as isize; + match mask { + // IIO_CHAN_INFO_RAW: read the 12-bit raw angle value. + INFO_RAW => { + let hw = self.io_lock.lock(); + + // Read status register to verify magnet presence before + // reading the angle. + let status = hw.client.try_read8(AS5600_REG_STATUS as usize)?; + + // Check magnet presence (MD bit). Without a magnet the angle + // register contains stale/invalid data. + if (status & AS5600_STATUS_MD) == 0 { + return Err(ENODATA); + } + + // Word read at register 0x0C: SMBus read_word_data returns LE, + // AS5600 stores angle big-endian, so swap_bytes() is needed. + // Mutex ensures status + angle read is atomic. + // NOTE: Equivalent to C's i2c_smbus_read_word_swapped(). + // Long-term, regmap-rs with val_format_endian=Big handles + // this transparently at configuration level. + let raw = hw.client.try_read16(AS5600_REG_RAW_ANGLE_H as usize)?; + let angle = raw.swap_bytes() & AS5600_RAW_ANGLE_MASK; + Ok(IioVal::Int(angle as i32)) + } + // IIO_CHAN_INFO_SCALE: radians per LSB, 2*pi / 4096 = 0.001533981. + INFO_SCALE => { + Ok(IioVal::IntPlusNano(0, 1533981)) + } + _ => Err(EINVAL), + } + } + + fn channels(&self) -> &[iio_chan_spec] { + &AS5600_CHANNELS.0 + } +} + +#[pin_data] +struct As5600 { + #[pin] + _iio_dev: Device, +} + +impl Driver for As5600 { + type IdInfo = (); + type Data<'bound> = As5600; + + const I2C_ID_TABLE: Option> = Some(&I2C_TABLE); + const OF_ID_TABLE: Option> = Some(&OF_TABLE); + + #[allow(refining_impl_trait)] + fn probe<'bound>( + dev: &'bound I2cClient>, + _id_info: Option<&'bound Self::IdInfo>, + ) -> impl PinInit, Error> + 'bound { + try_pin_init!(As5600 { + _iio_dev: { + let client: ARef = dev.into(); + + let priv_init = pin_init!(As5600Priv { + io_lock <- new_mutex!(As5600HwState { + client + }), + }); + + let iio_dev = Device::build_device(dev.as_ref(), c"as5600", priv_init)?; + let registered = iio_dev.register(&crate::THIS_MODULE)?; + dev_dbg!(dev.as_ref(), "AS5600 magnetic position sensor ready\n"); + registered + } + }) + } +} -- 2.50.0