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-rw-r--r--rust/kernel/dma.rs355
1 files changed, 314 insertions, 41 deletions
diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index a33261c62e0c..b320779ea26f 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -5,14 +5,156 @@
//! C header: [`include/linux/dma-mapping.h`](srctree/include/linux/dma-mapping.h)
use crate::{
- bindings, build_assert,
- device::{Bound, Device},
- error::code::*,
- error::Result,
+ bindings, build_assert, device,
+ device::{Bound, Core},
+ error::{to_result, Result},
+ prelude::*,
transmute::{AsBytes, FromBytes},
types::ARef,
};
+/// Trait to be implemented by DMA capable bus devices.
+///
+/// The [`dma::Device`](Device) trait should be implemented by bus specific device representations,
+/// where the underlying bus is DMA capable, such as [`pci::Device`](::kernel::pci::Device) or
+/// [`platform::Device`](::kernel::platform::Device).
+pub trait Device: AsRef<device::Device<Core>> {
+ /// Set up the device's DMA streaming addressing capabilities.
+ ///
+ /// This method is usually called once from `probe()` as soon as the device capabilities are
+ /// known.
+ ///
+ /// # Safety
+ ///
+ /// This method must not be called concurrently with any DMA allocation or mapping primitives,
+ /// such as [`CoherentAllocation::alloc_attrs`].
+ unsafe fn dma_set_mask(&self, mask: DmaMask) -> Result {
+ // SAFETY:
+ // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid.
+ // - The safety requirement of this function guarantees that there are no concurrent calls
+ // to DMA allocation and mapping primitives using this mask.
+ to_result(unsafe { bindings::dma_set_mask(self.as_ref().as_raw(), mask.value()) })
+ }
+
+ /// Set up the device's DMA coherent addressing capabilities.
+ ///
+ /// This method is usually called once from `probe()` as soon as the device capabilities are
+ /// known.
+ ///
+ /// # Safety
+ ///
+ /// This method must not be called concurrently with any DMA allocation or mapping primitives,
+ /// such as [`CoherentAllocation::alloc_attrs`].
+ unsafe fn dma_set_coherent_mask(&self, mask: DmaMask) -> Result {
+ // SAFETY:
+ // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid.
+ // - The safety requirement of this function guarantees that there are no concurrent calls
+ // to DMA allocation and mapping primitives using this mask.
+ to_result(unsafe { bindings::dma_set_coherent_mask(self.as_ref().as_raw(), mask.value()) })
+ }
+
+ /// Set up the device's DMA addressing capabilities.
+ ///
+ /// This is a combination of [`Device::dma_set_mask`] and [`Device::dma_set_coherent_mask`].
+ ///
+ /// This method is usually called once from `probe()` as soon as the device capabilities are
+ /// known.
+ ///
+ /// # Safety
+ ///
+ /// This method must not be called concurrently with any DMA allocation or mapping primitives,
+ /// such as [`CoherentAllocation::alloc_attrs`].
+ unsafe fn dma_set_mask_and_coherent(&self, mask: DmaMask) -> Result {
+ // SAFETY:
+ // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid.
+ // - The safety requirement of this function guarantees that there are no concurrent calls
+ // to DMA allocation and mapping primitives using this mask.
+ to_result(unsafe {
+ bindings::dma_set_mask_and_coherent(self.as_ref().as_raw(), mask.value())
+ })
+ }
+}
+
+/// A DMA mask that holds a bitmask with the lowest `n` bits set.
+///
+/// Use [`DmaMask::new`] or [`DmaMask::try_new`] to construct a value. Values
+/// are guaranteed to never exceed the bit width of `u64`.
+///
+/// This is the Rust equivalent of the C macro `DMA_BIT_MASK()`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct DmaMask(u64);
+
+impl DmaMask {
+ /// Constructs a `DmaMask` with the lowest `n` bits set to `1`.
+ ///
+ /// For `n <= 64`, sets exactly the lowest `n` bits.
+ /// For `n > 64`, results in a build error.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use kernel::dma::DmaMask;
+ ///
+ /// let mask0 = DmaMask::new::<0>();
+ /// assert_eq!(mask0.value(), 0);
+ ///
+ /// let mask1 = DmaMask::new::<1>();
+ /// assert_eq!(mask1.value(), 0b1);
+ ///
+ /// let mask64 = DmaMask::new::<64>();
+ /// assert_eq!(mask64.value(), u64::MAX);
+ ///
+ /// // Build failure.
+ /// // let mask_overflow = DmaMask::new::<100>();
+ /// ```
+ #[inline]
+ pub const fn new<const N: u32>() -> Self {
+ let Ok(mask) = Self::try_new(N) else {
+ build_error!("Invalid DMA Mask.");
+ };
+
+ mask
+ }
+
+ /// Constructs a `DmaMask` with the lowest `n` bits set to `1`.
+ ///
+ /// For `n <= 64`, sets exactly the lowest `n` bits.
+ /// For `n > 64`, returns [`EINVAL`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use kernel::dma::DmaMask;
+ ///
+ /// let mask0 = DmaMask::try_new(0)?;
+ /// assert_eq!(mask0.value(), 0);
+ ///
+ /// let mask1 = DmaMask::try_new(1)?;
+ /// assert_eq!(mask1.value(), 0b1);
+ ///
+ /// let mask64 = DmaMask::try_new(64)?;
+ /// assert_eq!(mask64.value(), u64::MAX);
+ ///
+ /// let mask_overflow = DmaMask::try_new(100);
+ /// assert!(mask_overflow.is_err());
+ /// # Ok::<(), Error>(())
+ /// ```
+ #[inline]
+ pub const fn try_new(n: u32) -> Result<Self> {
+ Ok(Self(match n {
+ 0 => 0,
+ 1..=64 => u64::MAX >> (64 - n),
+ _ => return Err(EINVAL),
+ }))
+ }
+
+ /// Returns the underlying `u64` bitmask value.
+ #[inline]
+ pub const fn value(&self) -> u64 {
+ self.0
+ }
+}
+
/// Possible attributes associated with a DMA mapping.
///
/// They can be combined with the operators `|`, `&`, and `!`.
@@ -89,7 +231,7 @@ pub mod attrs {
/// Forces contiguous allocation of the buffer in physical memory.
pub const DMA_ATTR_FORCE_CONTIGUOUS: Attrs = Attrs(bindings::DMA_ATTR_FORCE_CONTIGUOUS);
- /// This is a hint to the DMA-mapping subsystem that it's probably not worth the time to try
+ /// Hints DMA-mapping subsystem that it's probably not worth the time to try
/// to allocate memory to in a way that gives better TLB efficiency.
pub const DMA_ATTR_ALLOC_SINGLE_PAGES: Attrs = Attrs(bindings::DMA_ATTR_ALLOC_SINGLE_PAGES);
@@ -97,7 +239,7 @@ pub mod attrs {
/// `__GFP_NOWARN`).
pub const DMA_ATTR_NO_WARN: Attrs = Attrs(bindings::DMA_ATTR_NO_WARN);
- /// Used to indicate that the buffer is fully accessible at an elevated privilege level (and
+ /// Indicates that the buffer is fully accessible at an elevated privilege level (and
/// ideally inaccessible or at least read-only at lesser-privileged levels).
pub const DMA_ATTR_PRIVILEGED: Attrs = Attrs(bindings::DMA_ATTR_PRIVILEGED);
}
@@ -105,7 +247,7 @@ pub mod attrs {
/// An abstraction of the `dma_alloc_coherent` API.
///
/// This is an abstraction around the `dma_alloc_coherent` API which is used to allocate and map
-/// large consistent DMA regions.
+/// large coherent DMA regions.
///
/// A [`CoherentAllocation`] instance contains a pointer to the allocated region (in the
/// processor's virtual address space) and the device address which can be given to the device
@@ -114,9 +256,11 @@ pub mod attrs {
///
/// # Invariants
///
-/// For the lifetime of an instance of [`CoherentAllocation`], the `cpu_addr` is a valid pointer
-/// to an allocated region of consistent memory and `dma_handle` is the DMA address base of
-/// the region.
+/// - For the lifetime of an instance of [`CoherentAllocation`], the `cpu_addr` is a valid pointer
+/// to an allocated region of coherent memory and `dma_handle` is the DMA address base of the
+/// region.
+/// - The size in bytes of the allocation is equal to `size_of::<T> * count`.
+/// - `size_of::<T> * count` fits into a `usize`.
// TODO
//
// DMA allocations potentially carry device resources (e.g.IOMMU mappings), hence for soundness
@@ -130,7 +274,7 @@ pub mod attrs {
// Hence, find a way to revoke the device resources of a `CoherentAllocation`, but not the
// entire `CoherentAllocation` including the allocated memory itself.
pub struct CoherentAllocation<T: AsBytes + FromBytes> {
- dev: ARef<Device>,
+ dev: ARef<device::Device>,
dma_handle: bindings::dma_addr_t,
count: usize,
cpu_addr: *mut T,
@@ -138,7 +282,7 @@ pub struct CoherentAllocation<T: AsBytes + FromBytes> {
}
impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
- /// Allocates a region of `size_of::<T> * count` of consistent memory.
+ /// Allocates a region of `size_of::<T> * count` of coherent memory.
///
/// # Examples
///
@@ -152,7 +296,7 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
/// # Ok::<(), Error>(()) }
/// ```
pub fn alloc_attrs(
- dev: &Device<Bound>,
+ dev: &device::Device<Bound>,
count: usize,
gfp_flags: kernel::alloc::Flags,
dma_attrs: Attrs,
@@ -179,9 +323,12 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
if ret.is_null() {
return Err(ENOMEM);
}
- // INVARIANT: We just successfully allocated a coherent region which is accessible for
- // `count` elements, hence the cpu address is valid. We also hold a refcounted reference
- // to the device.
+ // INVARIANT:
+ // - We just successfully allocated a coherent region which is accessible for
+ // `count` elements, hence the cpu address is valid. We also hold a refcounted reference
+ // to the device.
+ // - The allocated `size` is equal to `size_of::<T> * count`.
+ // - The allocated `size` fits into a `usize`.
Ok(Self {
dev: dev.into(),
dma_handle,
@@ -194,13 +341,28 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
/// Performs the same functionality as [`CoherentAllocation::alloc_attrs`], except the
/// `dma_attrs` is 0 by default.
pub fn alloc_coherent(
- dev: &Device<Bound>,
+ dev: &device::Device<Bound>,
count: usize,
gfp_flags: kernel::alloc::Flags,
) -> Result<CoherentAllocation<T>> {
CoherentAllocation::alloc_attrs(dev, count, gfp_flags, Attrs(0))
}
+ /// Returns the number of elements `T` in this allocation.
+ ///
+ /// Note that this is not the size of the allocation in bytes, which is provided by
+ /// [`Self::size`].
+ pub fn count(&self) -> usize {
+ self.count
+ }
+
+ /// Returns the size in bytes of this allocation.
+ pub fn size(&self) -> usize {
+ // INVARIANT: The type invariant of `Self` guarantees that `size_of::<T> * count` fits into
+ // a `usize`.
+ self.count * core::mem::size_of::<T>()
+ }
+
/// Returns the base address to the allocated region in the CPU's virtual address space.
pub fn start_ptr(&self) -> *const T {
self.cpu_addr
@@ -212,12 +374,113 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
self.cpu_addr
}
- /// Returns a DMA handle which may given to the device as the DMA address base of
+ /// Returns a DMA handle which may be given to the device as the DMA address base of
/// the region.
pub fn dma_handle(&self) -> bindings::dma_addr_t {
self.dma_handle
}
+ /// Returns a DMA handle starting at `offset` (in units of `T`) which may be given to the
+ /// device as the DMA address base of the region.
+ ///
+ /// Returns `EINVAL` if `offset` is not within the bounds of the allocation.
+ pub fn dma_handle_with_offset(&self, offset: usize) -> Result<bindings::dma_addr_t> {
+ if offset >= self.count {
+ Err(EINVAL)
+ } else {
+ // INVARIANT: The type invariant of `Self` guarantees that `size_of::<T> * count` fits
+ // into a `usize`, and `offset` is inferior to `count`.
+ Ok(self.dma_handle + (offset * core::mem::size_of::<T>()) as bindings::dma_addr_t)
+ }
+ }
+
+ /// Common helper to validate a range applied from the allocated region in the CPU's virtual
+ /// address space.
+ fn validate_range(&self, offset: usize, count: usize) -> Result {
+ if offset.checked_add(count).ok_or(EOVERFLOW)? > self.count {
+ return Err(EINVAL);
+ }
+ Ok(())
+ }
+
+ /// Returns the data from the region starting from `offset` as a slice.
+ /// `offset` and `count` are in units of `T`, not the number of bytes.
+ ///
+ /// For ringbuffer type of r/w access or use-cases where the pointer to the live data is needed,
+ /// [`CoherentAllocation::start_ptr`] or [`CoherentAllocation::start_ptr_mut`] could be used
+ /// instead.
+ ///
+ /// # Safety
+ ///
+ /// * Callers must ensure that the device does not read/write to/from memory while the returned
+ /// slice is live.
+ /// * Callers must ensure that this call does not race with a write to the same region while
+ /// the returned slice is live.
+ pub unsafe fn as_slice(&self, offset: usize, count: usize) -> Result<&[T]> {
+ self.validate_range(offset, count)?;
+ // SAFETY:
+ // - The pointer is valid due to type invariant on `CoherentAllocation`,
+ // we've just checked that the range and index is within bounds. The immutability of the
+ // data is also guaranteed by the safety requirements of the function.
+ // - `offset + count` can't overflow since it is smaller than `self.count` and we've checked
+ // that `self.count` won't overflow early in the constructor.
+ Ok(unsafe { core::slice::from_raw_parts(self.cpu_addr.add(offset), count) })
+ }
+
+ /// Performs the same functionality as [`CoherentAllocation::as_slice`], except that a mutable
+ /// slice is returned.
+ ///
+ /// # Safety
+ ///
+ /// * Callers must ensure that the device does not read/write to/from memory while the returned
+ /// slice is live.
+ /// * Callers must ensure that this call does not race with a read or write to the same region
+ /// while the returned slice is live.
+ pub unsafe fn as_slice_mut(&self, offset: usize, count: usize) -> Result<&mut [T]> {
+ self.validate_range(offset, count)?;
+ // SAFETY:
+ // - The pointer is valid due to type invariant on `CoherentAllocation`,
+ // we've just checked that the range and index is within bounds. The immutability of the
+ // data is also guaranteed by the safety requirements of the function.
+ // - `offset + count` can't overflow since it is smaller than `self.count` and we've checked
+ // that `self.count` won't overflow early in the constructor.
+ Ok(unsafe { core::slice::from_raw_parts_mut(self.cpu_addr.add(offset), count) })
+ }
+
+ /// Writes data to the region starting from `offset`. `offset` is in units of `T`, not the
+ /// number of bytes.
+ ///
+ /// # Safety
+ ///
+ /// * Callers must ensure that the device does not read/write to/from memory while the returned
+ /// slice is live.
+ /// * Callers must ensure that this call does not race with a read or write to the same region
+ /// that overlaps with this write.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// # fn test(alloc: &mut kernel::dma::CoherentAllocation<u8>) -> Result {
+ /// let somedata: [u8; 4] = [0xf; 4];
+ /// let buf: &[u8] = &somedata;
+ /// // SAFETY: There is no concurrent HW operation on the device and no other R/W access to the
+ /// // region.
+ /// unsafe { alloc.write(buf, 0)?; }
+ /// # Ok::<(), Error>(()) }
+ /// ```
+ pub unsafe fn write(&self, src: &[T], offset: usize) -> Result {
+ self.validate_range(offset, src.len())?;
+ // SAFETY:
+ // - The pointer is valid due to type invariant on `CoherentAllocation`
+ // and we've just checked that the range and index is within bounds.
+ // - `offset + count` can't overflow since it is smaller than `self.count` and we've checked
+ // that `self.count` won't overflow early in the constructor.
+ unsafe {
+ core::ptr::copy_nonoverlapping(src.as_ptr(), self.cpu_addr.add(offset), src.len())
+ };
+ Ok(())
+ }
+
/// Returns a pointer to an element from the region with bounds checking. `offset` is in
/// units of `T`, not the number of bytes.
///
@@ -328,20 +591,24 @@ unsafe impl<T: AsBytes + FromBytes + Send> Send for CoherentAllocation<T> {}
#[macro_export]
macro_rules! dma_read {
($dma:expr, $idx: expr, $($field:tt)*) => {{
- let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
- // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be
- // dereferenced. The compiler also further validates the expression on whether `field`
- // is a member of `item` when expanded by the macro.
- unsafe {
- let ptr_field = ::core::ptr::addr_of!((*item) $($field)*);
- $crate::dma::CoherentAllocation::field_read(&$dma, ptr_field)
- }
+ (|| -> ::core::result::Result<_, $crate::error::Error> {
+ let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
+ // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be
+ // dereferenced. The compiler also further validates the expression on whether `field`
+ // is a member of `item` when expanded by the macro.
+ unsafe {
+ let ptr_field = ::core::ptr::addr_of!((*item) $($field)*);
+ ::core::result::Result::Ok(
+ $crate::dma::CoherentAllocation::field_read(&$dma, ptr_field)
+ )
+ }
+ })()
}};
($dma:ident [ $idx:expr ] $($field:tt)* ) => {
- $crate::dma_read!($dma, $idx, $($field)*);
+ $crate::dma_read!($dma, $idx, $($field)*)
};
($($dma:ident).* [ $idx:expr ] $($field:tt)* ) => {
- $crate::dma_read!($($dma).*, $idx, $($field)*);
+ $crate::dma_read!($($dma).*, $idx, $($field)*)
};
}
@@ -368,24 +635,30 @@ macro_rules! dma_read {
#[macro_export]
macro_rules! dma_write {
($dma:ident [ $idx:expr ] $($field:tt)*) => {{
- $crate::dma_write!($dma, $idx, $($field)*);
+ $crate::dma_write!($dma, $idx, $($field)*)
}};
($($dma:ident).* [ $idx:expr ] $($field:tt)* ) => {{
- $crate::dma_write!($($dma).*, $idx, $($field)*);
+ $crate::dma_write!($($dma).*, $idx, $($field)*)
}};
($dma:expr, $idx: expr, = $val:expr) => {
- let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
- // SAFETY: `item_from_index` ensures that `item` is always a valid item.
- unsafe { $crate::dma::CoherentAllocation::field_write(&$dma, item, $val) }
+ (|| -> ::core::result::Result<_, $crate::error::Error> {
+ let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
+ // SAFETY: `item_from_index` ensures that `item` is always a valid item.
+ unsafe { $crate::dma::CoherentAllocation::field_write(&$dma, item, $val) }
+ ::core::result::Result::Ok(())
+ })()
};
($dma:expr, $idx: expr, $(.$field:ident)* = $val:expr) => {
- let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
- // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be
- // dereferenced. The compiler also further validates the expression on whether `field`
- // is a member of `item` when expanded by the macro.
- unsafe {
- let ptr_field = ::core::ptr::addr_of_mut!((*item) $(.$field)*);
- $crate::dma::CoherentAllocation::field_write(&$dma, ptr_field, $val)
- }
+ (|| -> ::core::result::Result<_, $crate::error::Error> {
+ let item = $crate::dma::CoherentAllocation::item_from_index(&$dma, $idx)?;
+ // SAFETY: `item_from_index` ensures that `item` is always a valid pointer and can be
+ // dereferenced. The compiler also further validates the expression on whether `field`
+ // is a member of `item` when expanded by the macro.
+ unsafe {
+ let ptr_field = ::core::ptr::addr_of_mut!((*item) $(.$field)*);
+ $crate::dma::CoherentAllocation::field_write(&$dma, ptr_field, $val)
+ }
+ ::core::result::Result::Ok(())
+ })()
};
}
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