* [RFC PATCH v7 1/4] rust: io: add FallibleIoCapable
2026-11-09 15:57 [RFC PATCH v7 0/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
@ 2026-11-09 15:57 ` Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 2/4] i2c: rust: implement SMBus access via IoBackend Muchamad Coirul Anwar
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Muchamad Coirul Anwar @ 2026-11-09 15:57 UTC (permalink / raw)
To: Jonathan Cameron, Miguel Ojeda, Igor Korotin, Danilo Krummrich
Cc: David Lechner, Alice Ryhl, Daniel Almeida, Mark Brown,
Andi Shyti, Shuai Liu, linux-iio, linux-i2c, rust-for-linux,
driver-core, linux-kernel
Add a fallible I/O capability for backends whose accesses may fail
independently of address validation.
Route try_read, try_write, try_write_reg, and try_update through the
fallible capability. Provide a blanket implementation for infallible
IoCapable backends so existing users retain their current behavior.
This allows transport-backed implementations such as I2C to expose only
fallible access while keeping infallible operations unavailable.
Link: https://lore.kernel.org/all/DJVQ852J7SOH.26YBIJTQ9B66G@kernel.org/
Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
---
rust/kernel/io.rs | 62 ++++++++++++++++++++++++++++++++++-------------
1 file changed, 45 insertions(+), 17 deletions(-)
diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs
index a877df11a03e..b93a540c28da 100644
--- a/rust/kernel/io.rs
+++ b/rust/kernel/io.rs
@@ -356,6 +356,31 @@ pub trait IoCapable<T>: IoBackend {
fn io_write<'a>(view: Self::View<'a, T>, value: T);
}
+/// I/O backend capability for operations that may fail independently of address validation.
+///
+/// Infallible backends implementing [`IoCapable`] also support fallible operations. Backends
+/// implementing only this trait cannot use the infallible [`Io`] accessors.
+pub trait FallibleIoCapable<T>: IoBackend {
+ /// Read from `view`, returning a transport error if the operation fails.
+ fn io_try_read<'a>(view: Self::View<'a, T>) -> Result<T>;
+
+ /// Write `value` to `view`, returning a transport error if the operation fails.
+ fn io_try_write<'a>(view: Self::View<'a, T>, value: T) -> Result;
+}
+
+impl<B: IoCapable<T>, T> FallibleIoCapable<T> for B {
+ #[inline(always)]
+ fn io_try_read<'a>(view: Self::View<'a, T>) -> Result<T> {
+ Ok(Self::io_read(view))
+ }
+
+ #[inline(always)]
+ fn io_try_write<'a>(view: Self::View<'a, T>, value: T) -> Result {
+ Self::io_write(view, value);
+ Ok(())
+ }
+}
+
/// Trait indicating that an I/O backend supports memory copy operations.
pub trait IoCopyable: IoBackend {
/// Copy contents of `view` to `buffer`.
@@ -759,7 +784,7 @@ fn copy_to_slice(self, data: &mut [u8])
fn try_read8(self, offset: usize) -> Result<u8>
where
usize: IoLoc<Self::Target, u8>,
- Self::Backend: IoCapable<u8>,
+ Self::Backend: FallibleIoCapable<u8>,
{
self.try_read(offset)
}
@@ -769,7 +794,7 @@ fn try_read8(self, offset: usize) -> Result<u8>
fn try_read16(self, offset: usize) -> Result<u16>
where
usize: IoLoc<Self::Target, u16>,
- Self::Backend: IoCapable<u16>,
+ Self::Backend: FallibleIoCapable<u16>,
{
self.try_read(offset)
}
@@ -779,7 +804,7 @@ fn try_read16(self, offset: usize) -> Result<u16>
fn try_read32(self, offset: usize) -> Result<u32>
where
usize: IoLoc<Self::Target, u32>,
- Self::Backend: IoCapable<u32>,
+ Self::Backend: FallibleIoCapable<u32>,
{
self.try_read(offset)
}
@@ -789,7 +814,7 @@ fn try_read32(self, offset: usize) -> Result<u32>
fn try_read64(self, offset: usize) -> Result<u64>
where
usize: IoLoc<Self::Target, u64>,
- Self::Backend: IoCapable<u64>,
+ Self::Backend: FallibleIoCapable<u64>,
{
self.try_read(offset)
}
@@ -799,7 +824,7 @@ fn try_read64(self, offset: usize) -> Result<u64>
fn try_write8(self, value: u8, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u8>,
- Self::Backend: IoCapable<u8>,
+ Self::Backend: FallibleIoCapable<u8>,
{
self.try_write(offset, value)
}
@@ -809,7 +834,7 @@ fn try_write8(self, value: u8, offset: usize) -> Result
fn try_write16(self, value: u16, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u16>,
- Self::Backend: IoCapable<u16>,
+ Self::Backend: FallibleIoCapable<u16>,
{
self.try_write(offset, value)
}
@@ -819,7 +844,7 @@ fn try_write16(self, value: u16, offset: usize) -> Result
fn try_write32(self, value: u32, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u32>,
- Self::Backend: IoCapable<u32>,
+ Self::Backend: FallibleIoCapable<u32>,
{
self.try_write(offset, value)
}
@@ -829,7 +854,7 @@ fn try_write32(self, value: u32, offset: usize) -> Result
fn try_write64(self, value: u64, offset: usize) -> Result
where
usize: IoLoc<Self::Target, u64>,
- Self::Backend: IoCapable<u64>,
+ Self::Backend: FallibleIoCapable<u64>,
{
self.try_write(offset, value)
}
@@ -958,9 +983,12 @@ fn try_read<T, L>(self, location: L) -> Result<T>
where
T: AsReprMut,
L: IoLoc<Self::Target, T>,
- Self::Backend: IoCapable<<T as AsRepr>::Repr>,
+ Self::Backend: FallibleIoCapable<<T as AsRepr>::Repr>,
{
- Ok(io_read!(self, try: location))
+ let view = io_project!(self, try: location);
+ Ok(T::from_repr(Self::Backend::io_try_read(io_view_as_repr(
+ view,
+ ))?))
}
/// Generic fallible write with runtime bounds check.
@@ -991,10 +1019,10 @@ fn try_write<T, L>(self, location: L, value: T) -> Result
where
T: AsRepr,
L: IoLoc<Self::Target, T>,
- Self::Backend: IoCapable<<T as AsRepr>::Repr>,
+ Self::Backend: FallibleIoCapable<<T as AsRepr>::Repr>,
{
- io_write!(self, try: location, value);
- Ok(())
+ let view = io_project!(self, try: location);
+ Self::Backend::io_try_write(io_view_as_repr(view), T::into_repr(value))
}
/// Generic fallible write of a fully-located register value.
@@ -1037,7 +1065,7 @@ fn try_write_reg<T, L, V>(self, value: V) -> Result
T: AsRepr,
L: IoLoc<Self::Target, T>,
V: LocatedRegister<Self::Target, Location = L, Value = T>,
- Self::Backend: IoCapable<<T as AsRepr>::Repr>,
+ Self::Backend: FallibleIoCapable<<T as AsRepr>::Repr>,
{
let (location, value) = value.into_io_op();
@@ -1071,12 +1099,12 @@ fn try_update<T, L, F>(self, location: L, f: F) -> Result
where
T: AsReprMut,
L: IoLoc<Self::Target, T>,
- Self::Backend: IoCapable<<T as AsRepr>::Repr>,
+ Self::Backend: FallibleIoCapable<<T as AsRepr>::Repr>,
F: FnOnce(T) -> T,
{
let view = io_project!(self, try: location);
- view.write_val(f(view.read_val()));
- Ok(())
+ let value = T::from_repr(Self::Backend::io_try_read(io_view_as_repr(view))?);
+ Self::Backend::io_try_write(io_view_as_repr(view), T::into_repr(f(value)))
}
/// Generic infallible read with compile-time bounds check.
^ permalink raw reply [flat|nested] 5+ messages in thread* [RFC PATCH v7 2/4] i2c: rust: implement SMBus access via IoBackend
2026-11-09 15:57 [RFC PATCH v7 0/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 1/4] rust: io: add FallibleIoCapable Muchamad Coirul Anwar
@ 2026-11-09 15:57 ` Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 3/4] rust: add minimal IIO subsystem abstractions Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 4/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
3 siblings, 0 replies; 5+ messages in thread
From: Muchamad Coirul Anwar @ 2026-11-09 15:57 UTC (permalink / raw)
To: Jonathan Cameron, Miguel Ojeda, Igor Korotin, Danilo Krummrich
Cc: David Lechner, Alice Ryhl, Daniel Almeida, Mark Brown,
Andi Shyti, Shuai Liu, linux-iio, linux-i2c, rust-for-linux,
driver-core, linux-kernel
Implement fallible SMBus byte and word access for bound I2C clients
using the generic I/O backend infrastructure.
I2C transactions may fail due to NACK, arbitration loss, or timeout, so
use FallibleIoCapable rather than the infallible IoCapable interface.
Propagate errors returned by the I2C core to callers.
Provide smbus_io() for byte-addressed register access and standalone
word helpers for layouts not represented by the Region-based view.
Also provide smbus_read_word_swapped() for devices that transmit the
high byte of a multi-byte value first.
Restrict these operations to I2cClient<Bound> so bus I/O is only available
while the client remains bound.
Keep the raw SMBus FFI calls and errno conversion in safe bound-client
methods. Include a generic no_run example for the word-read helper.
Suggested-by: Shuai Liu <847807867@qq.com>
Link: https://lore.kernel.org/all/tencent_173B7731E90B9624F9F82613DC3031B70907@qq.com/
Signed-off-by: Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
---
rust/kernel/i2c.rs | 235 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 235 insertions(+)
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 0487bae811fb..6f63bb8c6f93 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -14,8 +14,15 @@
devres::Devres,
driver,
error::*,
+ io::{
+ FallibleIoCapable,
+ IoBackend,
+ IoBase,
+ Region, //
+ },
of,
prelude::*,
+ ptr::KnownSize,
sync::aref::{
ARef,
AlwaysRefCounted, //
@@ -594,3 +601,231 @@ unsafe impl Send for Registration {}
// SAFETY: `Registration` offers no interior mutability (no mutation through &self
// and no mutable access is exposed)
unsafe impl Sync for Registration {}
+
+/// I/O backend for SMBus register access via I2C.
+///
+/// This backend implements only [`FallibleIoCapable`] and not
+/// [`crate::io::IoCapable`], because I2C/SMBus transactions can fail
+/// regardless of address validity. The infallible [`crate::io::Io::read`],
+/// [`crate::io::Io::write`], and [`crate::io::Io::update`] methods are
+/// therefore unavailable for this backend.
+pub struct I2cBackend;
+
+/// An SMBus view associated with a bound I2C client.
+///
+/// The pointer encodes a command offset and is never dereferenced as
+/// memory. Its type and, for dynamically sized targets, metadata describe
+/// the extent of the view.
+///
+/// # Invariants
+///
+/// The view is derived from the client's SMBus command region.
+/// Projections preserve the bounds of the source view.
+/// `client` remains valid and bound for the lifetime of the view.
+pub struct I2cView<'a, T: ?Sized> {
+ client: &'a I2cClient<device::Bound>,
+ ptr: *mut T,
+}
+
+impl<T: ?Sized> Copy for I2cView<'_, T> {}
+
+impl<T: ?Sized> Clone for I2cView<'_, T> {
+ #[inline]
+ fn clone(&self) -> Self {
+ *self
+ }
+}
+
+impl IoBackend for I2cBackend {
+ type View<'a, T: ?Sized + KnownSize> = I2cView<'a, T>;
+
+ #[inline]
+ fn as_ptr<'a, T: ?Sized + KnownSize>(view: Self::View<'a, T>) -> *mut T {
+ view.ptr
+ }
+
+ #[inline]
+ unsafe fn project_view<'a, T: ?Sized + KnownSize, U: ?Sized + KnownSize>(
+ view: Self::View<'a, T>,
+ ptr: *mut U,
+ ) -> Self::View<'a, U> {
+ // INVARIANT: Per safety requirement.
+ I2cView {
+ client: view.client,
+ ptr,
+ }
+ }
+}
+
+impl FallibleIoCapable<u8> for I2cBackend {
+ #[inline]
+ fn io_try_read<'a>(view: I2cView<'a, u8>) -> Result<u8> {
+ // `io_view()` ensures `offset + 1 <= 256`, so `addr()` is at most 255;
+ // the `as u8` cast below is therefore lossless.
+ let reg = Self::as_ptr(view).addr() as u8;
+ view.client.smbus_read_byte(reg)
+ }
+
+ #[inline]
+ fn io_try_write<'a>(view: I2cView<'a, u8>, value: u8) -> Result {
+ // `io_view()` ensures `offset + 1 <= 256`, so `addr()` is at most 255;
+ // the `as u8` cast below is therefore lossless.
+ let reg = Self::as_ptr(view).addr() as u8;
+ view.client.smbus_write_byte(reg, value)
+ }
+}
+
+/// The `Region<256>` view is byte-addressed. Consequently, its generic
+/// 16-bit operations reject odd command bytes and command byte `0xFF`.
+/// Devices whose command bytes each select an independent 16-bit register
+/// should use [`I2cClient::smbus_read_word`] or
+/// [`I2cClient::smbus_read_word_swapped`] directly.
+impl FallibleIoCapable<u16> for I2cBackend {
+ #[inline]
+ fn io_try_read<'a>(view: I2cView<'a, u16>) -> Result<u16> {
+ // `io_view()` ensures `offset + 2 <= 256`, so `addr()` is at most 254;
+ // the `as u8` cast below is therefore lossless.
+ let reg = Self::as_ptr(view).addr() as u8;
+ view.client.smbus_read_word(reg)
+ }
+
+ #[inline]
+ fn io_try_write<'a>(view: I2cView<'a, u16>, value: u16) -> Result {
+ // `io_view()` ensures `offset + 2 <= 256`, so `addr()` is at most 254;
+ // the `as u8` cast below is therefore lossless.
+ let reg = Self::as_ptr(view).addr() as u8;
+ view.client.smbus_write_word(reg, value)
+ }
+}
+
+impl<'a, T: ?Sized + KnownSize> IoBase<'a> for I2cView<'a, T> {
+ type Backend = I2cBackend;
+ type Target = T;
+
+ #[inline]
+ fn as_view(self) -> I2cView<'a, T> {
+ self
+ }
+}
+
+// SAFETY: The bound client borrow remains valid when the view is moved
+// between threads. The view exposes only SMBus transactions, which use
+// the I2C core's bus locking, and pointer projections that never
+// dereference the encoded address as memory. `T: Sync` preserves the
+// shared-view restriction.
+unsafe impl<T: ?Sized + Sync> Send for I2cView<'_, T> {}
+
+// SAFETY: Sharing a view permits concurrent SMBus transactions, which
+// use the I2C core's bus locking. The bound client remains valid for
+// the view's lifetime, and the encoded pointer is never dereferenced
+// as memory. `T: Sync` preserves the shared-view restriction.
+unsafe impl<T: ?Sized + Sync> Sync for I2cView<'_, T> {}
+
+impl I2cClient<device::Bound> {
+ /// Returns an I/O handle for SMBus register access on this I2C client.
+ ///
+ /// The returned handle provides fallible read and write methods for the
+ /// SMBus command byte range (0x00–0xFF). A command byte is a data byte which
+ /// often selects a register on the device. The 7-bit device address is handled
+ /// separately by the I2C core.
+ ///
+ /// [`crate::io::Io::try_read16`] and
+ /// [`crate::io::Io::try_write16`] on the returned handle reject
+ /// odd offsets because the [`Region`]-based bounds check requires
+ /// `offset % 2 == 0`. This model does not cover every SMBus register layout,
+ /// including layouts where auto-increment or auto-decrement results in command
+ /// bytes that appear unaligned. Use [`Self::smbus_read_word`] or
+ /// [`Self::smbus_read_word_swapped`] for word access at an odd command byte.
+ #[inline]
+ pub fn smbus_io(&self) -> I2cView<'_, Region<256>> {
+ // INVARIANT: The view borrows this bound client and covers the 256-byte
+ // SMBus command region.
+ //
+ // The provenance-free pointer encodes a command offset rather than a
+ // memory address. Its initial address is zero, and the region metadata
+ // supplies the length used for bounds checks. Projections select command
+ // offsets; SMBus accessors extract those offsets without dereferencing
+ // the pointer.
+ I2cView {
+ client: self,
+ ptr: Region::<256>::ptr_from_raw_parts_mut(core::ptr::without_provenance_mut(0), 256),
+ }
+ }
+
+ #[inline]
+ fn smbus_read_byte(&self, reg: u8) -> Result<u8> {
+ // SAFETY: `self.as_raw()` returns a valid `*mut struct i2c_client`
+ // pointer as guaranteed by the type invariant of `I2cClient`.
+ // `i2c_smbus_read_byte_data` accepts any u8 command byte.
+ let ret = unsafe { bindings::i2c_smbus_read_byte_data(self.as_raw(), reg) };
+ to_result(ret)?;
+ Ok(ret as u8)
+ }
+
+ #[inline]
+ fn smbus_write_byte(&self, reg: u8, value: u8) -> Result {
+ // SAFETY: `self.as_raw()` returns a valid `*mut struct i2c_client`
+ // pointer as guaranteed by the type invariant of `I2cClient`.
+ // `i2c_smbus_write_byte_data` accepts any u8 command byte and value.
+ let ret = unsafe { bindings::i2c_smbus_write_byte_data(self.as_raw(), reg, value) };
+ to_result(ret)
+ }
+
+ /// Reads the 16-bit SMBus word value returned for a command.
+ ///
+ /// Wraps `i2c_smbus_read_word_data`. The `reg` parameter is the SMBus
+ /// command byte (0x00–0xFF), a data byte which often selects a register on
+ /// the device. SMBus transmits the low byte first.
+ ///
+ /// Use [`Self::smbus_read_word_swapped`] for devices that transmit the
+ /// high byte of a multi-byte value first.
+ ///
+ /// Returns `Err` if the bus transaction fails, for example because of a
+ /// NACK, arbitration loss, or timeout.
+ #[inline]
+ pub fn smbus_read_word(&self, reg: u8) -> Result<u16> {
+ // SAFETY: `self.as_raw()` returns a valid `*mut struct i2c_client`
+ // pointer as guaranteed by the type invariant of `I2cClient`.
+ // `i2c_smbus_read_word_data` is safe to call with any valid client
+ // pointer and any u8 command byte.
+ let ret = unsafe { bindings::i2c_smbus_read_word_data(self.as_raw(), reg) };
+ to_result(ret)?;
+ Ok(ret as u16)
+ }
+
+ #[inline]
+ fn smbus_write_word(&self, reg: u8, value: u16) -> Result {
+ // SAFETY: `self.as_raw()` returns a valid `*mut struct i2c_client`
+ // pointer as guaranteed by the type invariant of `I2cClient`.
+ // `i2c_smbus_write_word_data` accepts any u8 command byte and u16 value.
+ let ret = unsafe { bindings::i2c_smbus_write_word_data(self.as_raw(), reg, value) };
+ to_result(ret)
+ }
+
+ /// Reads a 16-bit word from an SMBus command and swaps its two bytes.
+ ///
+ /// Wraps `i2c_smbus_read_word_data` and applies [`u16::swap_bytes`] to the
+ /// result. The `reg` parameter is the SMBus command byte (0x00–0xFF), a data
+ /// byte which often selects a register on the device.
+ ///
+ /// SMBus transmits the low byte first. This method swaps the returned bytes
+ /// for devices that transmit the high byte of a multi-byte value first.
+ ///
+ /// Returns `Err` if the bus transaction fails, for example because of a
+ /// NACK, arbitration loss, or timeout.
+ ///
+ /// # Examples
+ ///
+ /// ```no_run
+ /// use kernel::{device::Bound, i2c::I2cClient, prelude::*};
+ ///
+ /// # fn test(client: &I2cClient<Bound>) -> Result<u16> {
+ /// // Read a word from a device that transmits its high byte first.
+ /// client.smbus_read_word_swapped(0x0c)
+ /// # }
+ /// ```
+ #[inline]
+ pub fn smbus_read_word_swapped(&self, reg: u8) -> Result<u16> {
+ self.smbus_read_word(reg).map(u16::swap_bytes)
+ }
+}
^ permalink raw reply [flat|nested] 5+ messages in thread* [RFC PATCH v7 3/4] rust: add minimal IIO subsystem abstractions
2026-11-09 15:57 [RFC PATCH v7 0/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 1/4] rust: io: add FallibleIoCapable Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 2/4] i2c: rust: implement SMBus access via IoBackend Muchamad Coirul Anwar
@ 2026-11-09 15:57 ` Muchamad Coirul Anwar
2026-11-09 15:57 ` [RFC PATCH v7 4/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
3 siblings, 0 replies; 5+ messages in thread
From: Muchamad Coirul Anwar @ 2026-11-09 15:57 UTC (permalink / raw)
To: Jonathan Cameron, Miguel Ojeda, Igor Korotin, Danilo Krummrich
Cc: David Lechner, Alice Ryhl, Daniel Almeida, Mark Brown,
Andi Shyti, Shuai Liu, linux-iio, linux-i2c, rust-for-linux,
driver-core, linux-kernel
Add minimal Rust abstractions needed to register direct-mode IIO
devices exposing read_raw channel information.
Provide a type-safe IioChanInfo selector, IioVal return types, and an
IioDriver trait. Add a C callback trampoline that validates the channel
information selector, invokes the Rust driver, and converts IioVal into
the representation expected by the IIO core.
Use typestate to distinguish unregistered and registered devices.
Registration returns an owned registered device whose destructor
unregisters it before destroying its Rust private data and releasing
the allocation reference.
Allow private data to borrow resources tied to the bound parent
lifetime. This lets drivers capture bus-specific resources during probe
and use them directly from subsystem callbacks without recovering them
from a generic parent device.
Support read_raw in INDIO_DIRECT_MODE only. Buffers, triggers, events,
and write operations are not supported.
The registration ownership and bound-parent lifetimes are based on
Igor Korotin's rework.
Link: https://lore.kernel.org/all/179286358623.55649.5397316745104390556@linux.dev/
Suggested-by: Shuai Liu <847807867@qq.com>
Link: https://lore.kernel.org/all/tencent_173B7731E90B9624F9F82613DC3031B70907@qq.com/
Signed-off-by: Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
---
include/linux/iio/iio.h | 6 +-
rust/bindings/bindings_helper.h | 2 +
rust/kernel/iio.rs | 463 ++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 2 +
4 files changed, 471 insertions(+), 2 deletions(-)
create mode 100644 rust/kernel/iio.rs
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 9b63785d5aec..e2ffb2b35126 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -450,8 +450,10 @@ struct iio_trigger; /* forward declaration */
* @read_raw: function to request a value from the device.
* mask specifies which value. Note 0 means a reading of
* the channel in question. Return value will specify the
- * type of value returned by the device. val and val2 will
- * contain the elements making up the returned value.
+ * type of value returned by the device. val and val2
+ * point to writable integer storage valid for the
+ * duration of the callback. The return value determines
+ * which outputs contain meaningful data.
* @read_raw_multi: function to return values from the device.
* mask specifies which value. Note 0 means a reading of
* the channel in question. Return value will specify the
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 3791af0aadc7..c2e2fb32ebe3 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -64,6 +64,8 @@
#include <linux/fwctl.h>
#include <linux/fs.h>
#include <linux/i2c.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
#include <linux/interrupt.h>
#include <linux/io-pgtable.h>
#include <linux/ioport.h>
diff --git a/rust/kernel/iio.rs b/rust/kernel/iio.rs
new file mode 100644
index 000000000000..cd62b765b050
--- /dev/null
+++ b/rust/kernel/iio.rs
@@ -0,0 +1,463 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2026 Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
+//! IIO subsystem abstractions.
+//!
+//! Provides [`Device`] for allocating and registering an IIO device, and
+//! [`IioDriver`] for implementing `read_raw` callbacks. Implementing the
+//! trait requires validating the raw channel specifications.
+
+use crate::{
+ bindings::{
+ __iio_device_register,
+ iio_chan_spec,
+ iio_dev,
+ iio_device_alloc,
+ iio_device_free,
+ iio_device_unregister,
+ iio_info,
+ INDIO_DIRECT_MODE, //
+ },
+ device::{
+ self,
+ Bound, //
+ },
+ error::{
+ code::*,
+ to_result,
+ Result, //
+ },
+ prelude::*,
+ ThisModule, //
+};
+
+use core::{
+ ffi::c_int,
+ marker::PhantomData,
+ mem::{
+ forget,
+ size_of,
+ zeroed, //
+ },
+ num::NonZeroI32,
+ pin::Pin,
+ ptr::drop_in_place, //
+};
+
+use pin_init::{
+ pin_data,
+ pinned_drop, //
+};
+
+/// IIO value type: single integer (`IIO_VAL_INT`).
+pub const IIO_VAL_INT: c_int = crate::bindings::IIO_VAL_INT as c_int;
+
+/// IIO value type: integer plus micro part (`IIO_VAL_INT_PLUS_MICRO`).
+pub const IIO_VAL_INT_PLUS_MICRO: c_int = crate::bindings::IIO_VAL_INT_PLUS_MICRO as c_int;
+
+/// IIO value type: integer plus nano part (`IIO_VAL_INT_PLUS_NANO`).
+pub const IIO_VAL_INT_PLUS_NANO: c_int = crate::bindings::IIO_VAL_INT_PLUS_NANO as c_int;
+
+/// IIO value type: fractional (`IIO_VAL_FRACTIONAL`).
+pub const IIO_VAL_FRACTIONAL: c_int = crate::bindings::IIO_VAL_FRACTIONAL as c_int;
+
+/// Generates a Rust enum wrapper for C `enum iio_chan_info_enum`.
+///
+/// This macro creates a type-safe enum with automatic `TryFrom<u32>`
+/// conversion. Drivers match directly on `IioChanInfo` variants in
+/// `read_raw`, and the compiler enforces match exhaustiveness.
+/// Additional variants can be added as drivers require them.
+macro_rules! build_iio_chan_info_enum {
+ (
+ $(
+ $(#[$meta:meta])*
+ $rust_name:ident = $c_const:ident
+ ),* $(,)?
+ ) => {
+ /// Channel information selector for [`IioDriver::read_raw`].
+ ///
+ /// Wraps supported C `enum iio_chan_info_enum` values identifying
+ /// the requested channel information.
+ ///
+ /// Conversion from an unsupported value returns `EINVAL`.
+ #[repr(u32)]
+ #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+ pub enum IioChanInfo {
+ $(
+ $(#[$meta])*
+ $rust_name = bindings::$c_const,
+ )*
+ }
+ impl TryFrom<u32> for IioChanInfo {
+ type Error = Error;
+ fn try_from(value: u32) -> Result<Self, Self::Error> {
+ match value {
+ $( bindings::$c_const => Ok(IioChanInfo::$rust_name), )*
+ _ => Err(EINVAL),
+ }
+ }
+ }
+ };
+}
+
+build_iio_chan_info_enum! {
+ /// Raw unprocessed value from the channel (`IIO_CHAN_INFO_RAW`).
+ ///
+ /// For sensors, this is typically the ADC reading or register value
+ /// before any scaling or offset correction.
+ Raw = iio_chan_info_enum_IIO_CHAN_INFO_RAW,
+
+ /// Scale factor for converting raw values to channel units
+ /// (`IIO_CHAN_INFO_SCALE`).
+ ///
+ /// Apply any offset before scaling: `(raw + offset) * scale`.
+ /// The unit is defined by the IIO ABI for the channel type.
+ Scale = iio_chan_info_enum_IIO_CHAN_INFO_SCALE,
+}
+
+/// Represents the return value of a `read_raw` operation.
+///
+/// Each variant corresponds to an `IIO_VAL_*` constant and tells the
+/// IIO core how to format `val` and `val2` for userspace.
+pub enum IioVal {
+ /// A single integer value.
+ Int(i32),
+
+ /// A fractional value represented as `val / val2`.
+ /// The denominator is `NonZeroI32` to prevent division-by-zero in
+ /// `iio_format_value()`.
+ Fractional(i32, NonZeroI32),
+
+ /// An integer part and a fractional part in millionths
+ /// (`IIO_VAL_INT_PLUS_MICRO`).
+ ///
+ /// For negative values, put the sign on the integer part, or on the
+ /// fractional part when the integer part is zero. For example,
+ /// `IntPlusMicro(-1, 500_000)` represents -1.5, and
+ /// `IntPlusMicro(0, -500_000)` represents -0.5.
+ IntPlusMicro(i32, i32),
+
+ /// An integer part and a fractional part in billionths
+ /// (`IIO_VAL_INT_PLUS_NANO`).
+ ///
+ /// Uses the same sign convention as [`IioVal::IntPlusMicro`].
+ IntPlusNano(i32, i32),
+}
+
+/// Trait implemented by IIO driver private data.
+///
+/// # Safety
+///
+/// The channel specifications returned by `channels()` must satisfy the
+/// IIO core's requirements. Channel types, modifiers, strings, and
+/// pointer/count pairs must be valid. Referenced storage must remain
+/// valid for every access by the IIO core.
+///
+/// Channels must not expose events, buffers, extended attributes, or
+/// available-value attributes. This abstraction currently supports only
+/// channel information handled by its `read_raw` callback.
+pub unsafe trait IioDriver: Send + Sync {
+ /// Called by the IIO core to read channel information.
+ ///
+ /// `chan` identifies the channel, and `info` selects the requested
+ /// information, such as its raw value or scale. Implementors must
+ /// capture bus-specific resources during initialization rather than
+ /// deriving them from a generic parent reference.
+ fn read_raw(&self, chan: *const iio_chan_spec, info: IioChanInfo) -> Result<IioVal>;
+
+ /// Returns the channel specifications for this driver.
+ ///
+ /// The default implementation returns an empty slice.
+ fn channels(&self) -> &'static [iio_chan_spec] {
+ &[]
+ }
+}
+
+/// C-compatible trampoline for the `iio_info.read_raw` callback.
+///
+/// # Safety
+///
+/// Callers must ensure that:
+/// - `indio_dev` points to a valid `iio_dev` allocated with space for `T`.
+/// Its private data contains an initialized `T` that remains valid and
+/// may be shared for the duration of this callback.
+/// - `chan` points to a valid channel specification for `indio_dev`.
+/// - `val` and `val2` are non-null, properly aligned pointers to writable
+/// `c_int` storage valid for the duration of this callback.
+/// - The parent of `indio_dev` remains bound for the entire callback.
+/// Registration ownership and callback teardown must enforce this.
+unsafe extern "C" fn read_raw_callback<T: IioDriver>(
+ indio_dev: *mut iio_dev,
+ chan: *const iio_chan_spec,
+ val: *mut c_int,
+ val2: *mut c_int,
+ info: isize,
+) -> c_int {
+ // SAFETY: `indio_dev` is valid and was allocated with space for `T` in its
+ // private data area. The `priv_` field was initialized in `Device::build_device()`.
+ let priv_ptr = unsafe { (*indio_dev).priv_.cast::<T>() };
+ // SAFETY: The callback contract guarantees that `priv_ptr` points to an
+ // initialized `T` that remains valid for the duration of this callback.
+ let driver = unsafe { &*priv_ptr };
+
+ // `info` is `long` from C. Negative values and values > u32::MAX
+ // are unsupported iio_chan_info variants; both map to EINVAL.
+ let info_enum = match u32::try_from(info)
+ .ok()
+ .and_then(|value| IioChanInfo::try_from(value).ok())
+ {
+ Some(info) => info,
+ None => return EINVAL.to_errno(),
+ };
+
+ match driver.read_raw(chan, info_enum) {
+ Ok(IioVal::Int(v)) => {
+ // SAFETY: `val` is valid per the function's Safety contract above.
+ // `val2` is not written; `IIO_VAL_INT` signals to the IIO core
+ // that only `val` carries meaningful data.
+ unsafe {
+ *val = v;
+ }
+ IIO_VAL_INT
+ }
+ Ok(IioVal::Fractional(v, v2)) => {
+ // SAFETY: both `val` and `val2` are valid per the Safety contract.
+ unsafe {
+ *val = v;
+ *val2 = v2.get();
+ }
+ IIO_VAL_FRACTIONAL
+ }
+ Ok(IioVal::IntPlusMicro(v, v2)) => {
+ // SAFETY: both `val` and `val2` are valid per the Safety contract.
+ unsafe {
+ *val = v;
+ *val2 = v2;
+ }
+ IIO_VAL_INT_PLUS_MICRO
+ }
+ Ok(IioVal::IntPlusNano(v, v2)) => {
+ // SAFETY: both `val` and `val2` are valid per the Safety contract.
+ unsafe {
+ *val = v;
+ *val2 = v2;
+ }
+ IIO_VAL_INT_PLUS_NANO
+ }
+ Err(e) => e.to_errno(),
+ }
+}
+
+// Device<T, State>: IIO device wrapper with typestate.
+
+/// Marker type for an unregistered IIO device.
+pub struct Unregistered;
+
+/// Marker type for a registered IIO device.
+pub struct Registered;
+
+/// An initialized IIO device awaiting registration.
+pub struct UnregisteredDevice<T: IioDriver> {
+ device: Device<T>,
+}
+
+/// An owned IIO device with in-place initialized driver data.
+///
+/// Dropping a registered device unregisters it before destroying the driver
+/// data. Dropping either state then releases the allocation reference with
+/// `iio_device_free`.
+///
+/// # Invariants
+///
+/// - `indio_dev` points to an `iio_dev` allocated by `iio_device_alloc`,
+/// and this wrapper owns its allocation reference.
+/// - Its private data contains an initialized `T` that remains at a fixed
+/// address until it is destroyed.
+/// - `registered` is true exactly when this wrapper owns a successful
+/// registration that has not yet been undone.
+#[pin_data(PinnedDrop)]
+pub struct Device<T: IioDriver, State = Unregistered> {
+ indio_dev: *mut iio_dev,
+ registered: bool,
+ _p: PhantomData<(T, State)>,
+}
+
+// SAFETY: Moving the wrapper transfers ownership without moving the separately
+// allocated `iio_dev` or its private data. `T: Send` permits transferring the
+// private data to another thread.
+unsafe impl<T: IioDriver, State> Send for Device<T, State> {}
+
+// SAFETY: All `&self` access to the `iio_dev` is read-only or goes through the
+// IIO core which provides its own synchronization. `T` is required to be `Sync`.
+unsafe impl<T: IioDriver, State> Sync for Device<T, State> {}
+
+#[pinned_drop]
+impl<T: IioDriver, State> PinnedDrop for Device<T, State> {
+ fn drop(self: Pin<&mut Self>) {
+ if self.registered {
+ // SAFETY: `__iio_device_register` succeeded.
+ //
+ // iio_device_unregister() deletes the character device, disables
+ // buffers, clears `info` while holding `info_exist_lock`, and removes
+ // the remaining buffer sysfs state. Device removal also removes and
+ // drains its sysfs files. In-kernel read helpers that use
+ // `info_exist_lock` cannot race this `info` teardown.
+ //
+ // Any callback path not covered by those mechanisms requires a
+ // separate teardown proof before this abstraction can expose it.
+ unsafe { iio_device_unregister(self.indio_dev) };
+ }
+
+ // SAFETY: `priv_` was fully initialized in `build_device` via
+ // `pin_init::raw_try_init`. `drop_in_place` runs `T`'s destructor
+ // (including any pinned fields like Mutex). After that, `iio_device_free`
+ // calls `put_device` which decrements the kref. The underlying `iio_dev`
+ // memory is only freed when kref reaches 0.
+ unsafe {
+ let priv_ptr = (*self.indio_dev).priv_.cast::<T>();
+ drop_in_place(priv_ptr);
+ iio_device_free(self.indio_dev);
+ }
+ }
+}
+
+impl<T: IioDriver> Device<T> {
+ // SAFETY:
+ // - `read_raw_callback::<T>` is a valid function pointer whose signature
+ // matches the IIO core's `read_raw` contract.
+ // - All remaining fields are pointers or function pointers; zeroed values
+ // are NULL, and the IIO core checks for NULL before invoking any optional
+ // callback or dereferencing any optional attribute group.
+ const VTABLE: iio_info = iio_info {
+ read_raw: Some(read_raw_callback::<T>),
+ ..unsafe { zeroed() }
+ };
+
+ /// Allocates an unregistered IIO device and initializes its driver data
+ /// in place.
+ ///
+ /// `parent` becomes the IIO device's parent. `name` supplies its name.
+ /// Only `INDIO_DIRECT_MODE` is supported.
+ ///
+ /// Returns `EINVAL` if `modes` is not `INDIO_DIRECT_MODE`, if the
+ /// private-data size or channel count cannot be represented by the
+ /// corresponding C type, if `T` is zero-sized, or if the private
+ /// storage is not suitably aligned.
+ /// Allocation and initialization errors are propagated.
+ ///
+ /// Call [`UnregisteredDevice::register`] to register the device.
+ pub fn build_device<E>(
+ parent: &device::Device<Bound>,
+ name: &'static CStr,
+ modes: u32,
+ init: impl PinInit<T, E>,
+ ) -> Result<UnregisteredDevice<T>>
+ where
+ Error: From<E>,
+ {
+ if modes != INDIO_DIRECT_MODE {
+ return Err(EINVAL);
+ }
+
+ let modes = c_int::try_from(modes).map_err(|_| EINVAL)?;
+
+ let priv_size = i32::try_from(size_of::<T>()).map_err(|_| EINVAL)?;
+ if priv_size == 0 {
+ return Err(EINVAL);
+ }
+
+ // SAFETY: `parent.as_raw()` returns a valid `struct device` pointer.
+ // `iio_device_alloc` allocates an `iio_dev` with `sizeof(T)` bytes of
+ // private data. Returns NULL on failure.
+ let indio_dev = unsafe { iio_device_alloc(parent.as_raw(), priv_size) };
+ if indio_dev.is_null() {
+ return Err(ENOMEM);
+ }
+
+ // SAFETY: `indio_dev` is non-null and was just successfully allocated by
+ // `iio_device_alloc`. Accessing `priv_` yields a pointer to zeroed
+ // memory (kzalloc'd) sized for `T`.
+ let priv_ptr = unsafe { (*indio_dev).priv_.cast::<T>() };
+ if !priv_ptr.is_aligned() {
+ // SAFETY: `indio_dev` was allocated by `iio_device_alloc` and `priv_`
+ // has not been initialized, so no destructor needs to run.
+ unsafe { iio_device_free(indio_dev) };
+ return Err(EINVAL);
+ }
+
+ // SAFETY: `priv_ptr` is aligned and points to exclusively owned storage
+ // large enough for `T`. The private data remains at a fixed address in
+ // the separate IIO allocation until it is dropped. On initialization
+ // failure, the error path only frees the allocation.
+ let init_result = unsafe { pin_init::raw_try_init(priv_ptr, init) };
+ if let Err(e) = init_result {
+ // SAFETY: `pin_init` guarantees partial-init rollback internally.
+ // `priv_` memory was not fully initialized, so we only free the
+ // container without running `T`'s destructor.
+ unsafe { iio_device_free(indio_dev) };
+ return Err(Error::from(e));
+ }
+
+ let device = Self {
+ indio_dev,
+ registered: false,
+ _p: PhantomData,
+ };
+
+ // SAFETY: `priv_ptr` points to the initialized `T` owned by `device`.
+ // It remains valid for this shared borrow.
+ let channels = unsafe { (&*priv_ptr).channels() };
+ let num_channels = c_int::try_from(channels.len()).map_err(|_| EINVAL)?;
+
+ // SAFETY: `priv_ptr` is now fully initialized. We set up the IIO
+ // device fields:
+ // - `name` is a `'static` C string that outlives the device.
+ // - The reference to `VTABLE` is promoted to static storage.
+ // - `channels()` returns a static slice, so its backing storage
+ // outlives the `iio_dev` allocation.
+ // - `modes` was checked to be `INDIO_DIRECT_MODE`, so registration
+ // does not expose unsupported buffer or trigger paths.
+ // - `T`'s `IioDriver` safety contract guarantees that the channel
+ // specifications and their referenced storage satisfy the IIO
+ // core's requirements.
+
+ unsafe {
+ (*indio_dev).name = name.as_char_ptr();
+ (*indio_dev).info = &Self::VTABLE;
+ (*indio_dev).channels = channels.as_ptr();
+ (*indio_dev).num_channels = num_channels;
+ (*indio_dev).modes = modes;
+ }
+
+ Ok(UnregisteredDevice { device })
+ }
+}
+
+impl<T: IioDriver> UnregisteredDevice<T> {
+ /// Registers the IIO device.
+ ///
+ /// The caller owns the returned [`Device<T, Registered>`] and must keep it
+ /// alive while the registration should remain visible. Dropping it
+ /// unregisters the device and tears down the private data.
+ ///
+ /// On failure, the device is released and any successful registration is
+ /// undone.
+ #[inline]
+ pub fn register(self, module: &'static ThisModule) -> Result<Device<T, Registered>> {
+ let Self { device } = self;
+
+ // SAFETY: `device.indio_dev` is a valid, fully-initialized `iio_dev`
+ // allocated by `iio_device_alloc` with its name, info vtable, channels,
+ // modes, and private data all set. `module.as_ptr()` provides the owning
+ // module for proper reference counting.
+ to_result(unsafe { __iio_device_register(device.indio_dev, module.as_ptr()) })?;
+
+ let registered: Device<T, Registered> = Device {
+ indio_dev: device.indio_dev,
+ registered: true,
+ _p: PhantomData,
+ };
+ forget(device);
+
+ Ok(registered)
+ }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 1ab41129d557..dd883c1b374e 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -85,6 +85,8 @@
#[cfg(CONFIG_I2C = "y")]
pub mod i2c;
pub mod id_pool;
+#[cfg(CONFIG_IIO)]
+pub mod iio;
#[doc(hidden)]
pub mod impl_flags;
pub mod init;
^ permalink raw reply [flat|nested] 5+ messages in thread* [RFC PATCH v7 4/4] iio: position: add Rust driver for ams AS5600
2026-11-09 15:57 [RFC PATCH v7 0/4] iio: position: add Rust driver for ams AS5600 Muchamad Coirul Anwar
` (2 preceding siblings ...)
2026-11-09 15:57 ` [RFC PATCH v7 3/4] rust: add minimal IIO subsystem abstractions Muchamad Coirul Anwar
@ 2026-11-09 15:57 ` Muchamad Coirul Anwar
3 siblings, 0 replies; 5+ messages in thread
From: Muchamad Coirul Anwar @ 2026-11-09 15:57 UTC (permalink / raw)
To: Jonathan Cameron, Miguel Ojeda, Igor Korotin, Danilo Krummrich
Cc: David Lechner, Alice Ryhl, Daniel Almeida, Mark Brown,
Andi Shyti, Shuai Liu, linux-iio, linux-i2c, rust-for-linux,
driver-core, linux-kernel
Add a Rust driver for the ams AS5600 12-bit magnetic rotary position
sensor.
Expose the raw angle and scale through the IIO sysfs interface in direct
mode. Read the status register before each angle sample and return
ENODATA when the magnet-detected bit is clear. Serialize the status and
angle transaction sequence with a mutex and propagate I2C transport
errors directly to userspace.
Capture a bound I2C client reference during probe and store it in the
IIO private data. The registered IIO device carries the same bound
lifetime, keeping the client valid throughout read_raw callbacks.
The AS5600 stores the raw angle with the high byte at register 0x0c.
Use the byte-swapped SMBus word helper and mask the result to 12 bits.
Add usize bit and mask helpers for constructing the IIO channel
information mask.
The registered-device ownership and stored bound-client reference are
based on Igor Korotin's rework.
Link: https://lore.kernel.org/all/179286358623.55649.5397316745104390556@linux.dev/
Suggested-by: Shuai Liu <847807867@qq.com>
Link: https://lore.kernel.org/all/tencent_173B7731E90B9624F9F82613DC3031B70907@qq.com/
Signed-off-by: Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
---
drivers/iio/position/Kconfig | 11 ++
drivers/iio/position/Makefile | 1 +
drivers/iio/position/as5600.rs | 186 +++++++++++++++++++++++++++++++++
rust/kernel/bits.rs | 29 +++++
4 files changed, 227 insertions(+)
create mode 100644 drivers/iio/position/as5600.rs
diff --git a/drivers/iio/position/Kconfig b/drivers/iio/position/Kconfig
index 1576a6380b53..7c278f82f53d 100644
--- a/drivers/iio/position/Kconfig
+++ b/drivers/iio/position/Kconfig
@@ -6,6 +6,17 @@
menu "Linear and angular position sensors"
+config AS5600
+ tristate "ams AS5600 magnetic rotary position sensor"
+ depends on IIO=y && I2C=y && RUST
+ help
+ Support for the ams OSRAM AS5600 12-bit magnetic rotary
+ position sensor. Provides in_angl_raw (0-4095) and
+ in_angl_scale (radians per LSB) via sysfs.
+
+ 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..d5716501d48d
--- /dev/null
+++ b/drivers/iio/position/as5600.rs
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2026 Muchamad Coirul Anwar <muchamadcoirulanwar@gmail.com>
+//! Driver for ams AS5600 12-bit magnetic rotary position sensor.
+//!
+//! Exposes `in_angl_raw` and `in_angl_scale` through the IIO sysfs interface
+//! in `INDIO_DIRECT_MODE`.
+//!
+//! Datasheet: AS5600, document DS000365.
+
+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,
+ INDIO_DIRECT_MODE, //
+ },
+ bits::{
+ bit_u8,
+ bit_usize,
+ genmask_u16, //
+ },
+ device::{
+ Bound,
+ Core, //
+ },
+ error::code::ENODATA,
+ i2c::{
+ DeviceId,
+ Driver,
+ I2cClient,
+ IdTable, //
+ },
+ i2c_device_table,
+ iio::{
+ Device,
+ IioChanInfo,
+ IioDriver,
+ IioVal,
+ Registered, //
+ },
+ io::Io,
+ module_i2c_driver,
+ of,
+ of_device_table,
+ prelude::*,
+ sync::{
+ 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,
+ <As5600 as Driver>::IdInfo,
+ [(DeviceId::new(c"as5600"), ())]
+);
+
+of_device_table!(
+ OF_TABLE,
+ <As5600 as Driver>::IdInfo,
+ [(of::DeviceId::new(c"ams,as5600"), ())]
+);
+
+struct As5600Channels([iio_chan_spec; 1]);
+
+// SAFETY: `iio_chan_spec` is a plain C struct with no interior mutability.
+// All pointer fields (`event_spec`, `ext_info`, `extend_name`, etc.) are
+// NULL - set via `zeroed()` and never reassigned - so no shared mutable
+// state exists behind them. The static is a compile-time constant with no
+// `&mut` access path, making concurrent 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;
+ chan.info_mask_separate = bit_usize(iio_chan_info_enum_IIO_CHAN_INFO_RAW)
+ | bit_usize(iio_chan_info_enum_IIO_CHAN_INFO_SCALE);
+ [chan]
+});
+
+#[pin_data]
+struct As5600Priv<'a> {
+ client: &'a I2cClient<Bound>,
+ #[pin]
+ io_lock: Mutex<()>,
+}
+
+// SAFETY: I2C core serializes transfers, and the bound client remains valid
+// for the lifetime of the registered device and its callbacks.
+unsafe impl Send for As5600Priv<'_> {}
+// SAFETY: I2C core serializes transfers through the shared bound client.
+unsafe impl Sync for As5600Priv<'_> {}
+
+// SAFETY: AS5600_CHANNELS contains one valid, immutable IIO_ANGL channel
+// exposing only RAW and SCALE. It has no event or extension callbacks,
+// and all optional pointer fields are null.
+unsafe impl IioDriver for As5600Priv<'_> {
+ fn read_raw(&self, _chan: *const iio_chan_spec, info: IioChanInfo) -> Result<IioVal> {
+ match info {
+ IioChanInfo::Raw => {
+ let _guard = self.io_lock.lock();
+ let client = self.client;
+
+ let io = client.smbus_io();
+ // Read status register to verify magnet presence before
+ // reading the angle.
+ let status = io.try_read8(AS5600_REG_STATUS as usize)?;
+
+ if (status & AS5600_STATUS_MD) == 0 {
+ return Err(ENODATA);
+ }
+
+ // Word read at register 0x0C returns big-endian data.
+ // smbus_read_word_swapped() handles the byte swap.
+ let raw = client.smbus_read_word_swapped(AS5600_REG_RAW_ANGLE_H)?;
+ let angle = raw & AS5600_RAW_ANGLE_MASK;
+ Ok(IioVal::Int(i32::from(angle)))
+ }
+ // Scale factor: radians per LSB = 2*pi / 4096 ~= 0.001533981
+ IioChanInfo::Scale => Ok(IioVal::IntPlusNano(0, 1533981)),
+ }
+ }
+
+ fn channels(&self) -> &'static [iio_chan_spec] {
+ &AS5600_CHANNELS.0
+ }
+}
+
+struct As5600;
+
+#[pin_data]
+struct As5600Data<'bound> {
+ #[pin]
+ _iio_dev: Device<As5600Priv<'bound>, Registered>,
+}
+
+impl Driver for As5600 {
+ type IdInfo = ();
+ type Data<'bound> = As5600Data<'bound>;
+
+ const I2C_ID_TABLE: Option<IdTable<Self::IdInfo>> = Some(&I2C_TABLE);
+ const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
+
+ // `try_pin_init!` returns a concrete anonymous type that may expose more
+ // bounds than the trait signature declares (e.g. auto-traits like `Send`).
+ // This refinement of the RPITIT return type is intentional.
+ #[allow(refining_impl_trait)]
+ fn probe<'bound>(
+ dev: &'bound I2cClient<Core<'_>>,
+ _id_info: Option<&'bound Self::IdInfo>,
+ ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
+ try_pin_init!(As5600Data {
+ _iio_dev: {
+ // Deref coercion: I2cClient<Core<'_>> -> I2cClient<Bound>.
+ let client: &'bound I2cClient<Bound> = dev;
+
+ let priv_init = pin_init!(As5600Priv {
+ client,
+ io_lock <- new_mutex!(()),
+ });
+
+ let unregistered =
+ Device::build_device(dev.as_ref(), c"as5600", INDIO_DIRECT_MODE, priv_init)?;
+
+ unregistered.register(kernel::module::this_module::<crate::LocalModule>())?
+ }
+ })
+ }
+}
diff --git a/rust/kernel/bits.rs b/rust/kernel/bits.rs
index 2daead125626..a6537a668dd6 100644
--- a/rust/kernel/bits.rs
+++ b/rust/kernel/bits.rs
@@ -41,6 +41,7 @@ pub const fn [<bit_ $ty>](n: u32) -> $ty {
impl_bit_fn!(u32);
impl_bit_fn!(u16);
impl_bit_fn!(u8);
+impl_bit_fn!(usize);
macro_rules! impl_genmask_fn {
(
@@ -203,3 +204,31 @@ pub const fn [<genmask_ $ty>](range: RangeInclusive<u32>) -> $ty {
/// assert_eq!(genmask_u8(0..=7), u8::MAX);
/// ```
);
+
+impl_genmask_fn!(
+ usize,
+ /// # Examples
+ ///
+ /// ```
+ /// # #![expect(clippy::reversed_empty_ranges)]
+ /// # use kernel::bits::genmask_checked_usize;
+ /// assert_eq!(genmask_checked_usize(0..=0), Some(0b1));
+ /// assert_eq!(genmask_checked_usize(0..=3), Some(0b1111));
+ /// assert_eq!(genmask_checked_usize(1..=3), Some(0b1110));
+ ///
+ /// // `200` is out of the supported bit range on all platforms.
+ /// assert_eq!(genmask_checked_usize(0..=200), None);
+ ///
+ /// // Invalid range where the start is bigger than the end.
+ /// assert_eq!(genmask_checked_usize(5..=2), None);
+ /// ```
+ ,
+ /// # Examples
+ ///
+ /// ```
+ /// # use kernel::bits::genmask_usize;
+ /// assert_eq!(genmask_usize(0..=0), 0b1);
+ /// assert_eq!(genmask_usize(0..=3), 0b1111);
+ /// assert_eq!(genmask_usize(1..=3), 0b1110);
+ /// ```
+);
^ permalink raw reply [flat|nested] 5+ messages in thread