kernel/
io.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! Memory-mapped IO.
4//!
5//! C header: [`include/asm-generic/io.h`](srctree/include/asm-generic/io.h)
6
7use crate::error::{code::EINVAL, Result};
8use crate::{bindings, build_assert, ffi::c_void};
9
10pub mod mem;
11pub mod resource;
12
13pub use resource::Resource;
14
15/// Raw representation of an MMIO region.
16///
17/// By itself, the existence of an instance of this structure does not provide any guarantees that
18/// the represented MMIO region does exist or is properly mapped.
19///
20/// Instead, the bus specific MMIO implementation must convert this raw representation into an `Io`
21/// instance providing the actual memory accessors. Only by the conversion into an `Io` structure
22/// any guarantees are given.
23pub struct IoRaw<const SIZE: usize = 0> {
24    addr: usize,
25    maxsize: usize,
26}
27
28impl<const SIZE: usize> IoRaw<SIZE> {
29    /// Returns a new `IoRaw` instance on success, an error otherwise.
30    pub fn new(addr: usize, maxsize: usize) -> Result<Self> {
31        if maxsize < SIZE {
32            return Err(EINVAL);
33        }
34
35        Ok(Self { addr, maxsize })
36    }
37
38    /// Returns the base address of the MMIO region.
39    #[inline]
40    pub fn addr(&self) -> usize {
41        self.addr
42    }
43
44    /// Returns the maximum size of the MMIO region.
45    #[inline]
46    pub fn maxsize(&self) -> usize {
47        self.maxsize
48    }
49}
50
51/// IO-mapped memory region.
52///
53/// The creator (usually a subsystem / bus such as PCI) is responsible for creating the
54/// mapping, performing an additional region request etc.
55///
56/// # Invariant
57///
58/// `addr` is the start and `maxsize` the length of valid I/O mapped memory region of size
59/// `maxsize`.
60///
61/// # Examples
62///
63/// ```no_run
64/// # use kernel::{bindings, ffi::c_void, io::{Io, IoRaw}};
65/// # use core::ops::Deref;
66///
67/// // See also [`pci::Bar`] for a real example.
68/// struct IoMem<const SIZE: usize>(IoRaw<SIZE>);
69///
70/// impl<const SIZE: usize> IoMem<SIZE> {
71///     /// # Safety
72///     ///
73///     /// [`paddr`, `paddr` + `SIZE`) must be a valid MMIO region that is mappable into the CPUs
74///     /// virtual address space.
75///     unsafe fn new(paddr: usize) -> Result<Self>{
76///         // SAFETY: By the safety requirements of this function [`paddr`, `paddr` + `SIZE`) is
77///         // valid for `ioremap`.
78///         let addr = unsafe { bindings::ioremap(paddr as bindings::phys_addr_t, SIZE) };
79///         if addr.is_null() {
80///             return Err(ENOMEM);
81///         }
82///
83///         Ok(IoMem(IoRaw::new(addr as usize, SIZE)?))
84///     }
85/// }
86///
87/// impl<const SIZE: usize> Drop for IoMem<SIZE> {
88///     fn drop(&mut self) {
89///         // SAFETY: `self.0.addr()` is guaranteed to be properly mapped by `Self::new`.
90///         unsafe { bindings::iounmap(self.0.addr() as *mut c_void); };
91///     }
92/// }
93///
94/// impl<const SIZE: usize> Deref for IoMem<SIZE> {
95///    type Target = Io<SIZE>;
96///
97///    fn deref(&self) -> &Self::Target {
98///         // SAFETY: The memory range stored in `self` has been properly mapped in `Self::new`.
99///         unsafe { Io::from_raw(&self.0) }
100///    }
101/// }
102///
103///# fn no_run() -> Result<(), Error> {
104/// // SAFETY: Invalid usage for example purposes.
105/// let iomem = unsafe { IoMem::<{ core::mem::size_of::<u32>() }>::new(0xBAAAAAAD)? };
106/// iomem.write32(0x42, 0x0);
107/// assert!(iomem.try_write32(0x42, 0x0).is_ok());
108/// assert!(iomem.try_write32(0x42, 0x4).is_err());
109/// # Ok(())
110/// # }
111/// ```
112#[repr(transparent)]
113pub struct Io<const SIZE: usize = 0>(IoRaw<SIZE>);
114
115macro_rules! define_read {
116    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident -> $type_name:ty) => {
117        /// Read IO data from a given offset known at compile time.
118        ///
119        /// Bound checks are performed on compile time, hence if the offset is not known at compile
120        /// time, the build will fail.
121        $(#[$attr])*
122        #[inline]
123        pub fn $name(&self, offset: usize) -> $type_name {
124            let addr = self.io_addr_assert::<$type_name>(offset);
125
126            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
127            unsafe { bindings::$c_fn(addr as *const c_void) }
128        }
129
130        /// Read IO data from a given offset.
131        ///
132        /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
133        /// out of bounds.
134        $(#[$attr])*
135        pub fn $try_name(&self, offset: usize) -> Result<$type_name> {
136            let addr = self.io_addr::<$type_name>(offset)?;
137
138            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
139            Ok(unsafe { bindings::$c_fn(addr as *const c_void) })
140        }
141    };
142}
143
144macro_rules! define_write {
145    ($(#[$attr:meta])* $name:ident, $try_name:ident, $c_fn:ident <- $type_name:ty) => {
146        /// Write IO data from a given offset known at compile time.
147        ///
148        /// Bound checks are performed on compile time, hence if the offset is not known at compile
149        /// time, the build will fail.
150        $(#[$attr])*
151        #[inline]
152        pub fn $name(&self, value: $type_name, offset: usize) {
153            let addr = self.io_addr_assert::<$type_name>(offset);
154
155            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
156            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
157        }
158
159        /// Write IO data from a given offset.
160        ///
161        /// Bound checks are performed on runtime, it fails if the offset (plus the type size) is
162        /// out of bounds.
163        $(#[$attr])*
164        pub fn $try_name(&self, value: $type_name, offset: usize) -> Result {
165            let addr = self.io_addr::<$type_name>(offset)?;
166
167            // SAFETY: By the type invariant `addr` is a valid address for MMIO operations.
168            unsafe { bindings::$c_fn(value, addr as *mut c_void) }
169            Ok(())
170        }
171    };
172}
173
174impl<const SIZE: usize> Io<SIZE> {
175    /// Converts an `IoRaw` into an `Io` instance, providing the accessors to the MMIO mapping.
176    ///
177    /// # Safety
178    ///
179    /// Callers must ensure that `addr` is the start of a valid I/O mapped memory region of size
180    /// `maxsize`.
181    pub unsafe fn from_raw(raw: &IoRaw<SIZE>) -> &Self {
182        // SAFETY: `Io` is a transparent wrapper around `IoRaw`.
183        unsafe { &*core::ptr::from_ref(raw).cast() }
184    }
185
186    /// Returns the base address of this mapping.
187    #[inline]
188    pub fn addr(&self) -> usize {
189        self.0.addr()
190    }
191
192    /// Returns the maximum size of this mapping.
193    #[inline]
194    pub fn maxsize(&self) -> usize {
195        self.0.maxsize()
196    }
197
198    #[inline]
199    const fn offset_valid<U>(offset: usize, size: usize) -> bool {
200        let type_size = core::mem::size_of::<U>();
201        if let Some(end) = offset.checked_add(type_size) {
202            end <= size && offset % type_size == 0
203        } else {
204            false
205        }
206    }
207
208    #[inline]
209    fn io_addr<U>(&self, offset: usize) -> Result<usize> {
210        if !Self::offset_valid::<U>(offset, self.maxsize()) {
211            return Err(EINVAL);
212        }
213
214        // Probably no need to check, since the safety requirements of `Self::new` guarantee that
215        // this can't overflow.
216        self.addr().checked_add(offset).ok_or(EINVAL)
217    }
218
219    #[inline]
220    fn io_addr_assert<U>(&self, offset: usize) -> usize {
221        build_assert!(Self::offset_valid::<U>(offset, SIZE));
222
223        self.addr() + offset
224    }
225
226    define_read!(read8, try_read8, readb -> u8);
227    define_read!(read16, try_read16, readw -> u16);
228    define_read!(read32, try_read32, readl -> u32);
229    define_read!(
230        #[cfg(CONFIG_64BIT)]
231        read64,
232        try_read64,
233        readq -> u64
234    );
235
236    define_read!(read8_relaxed, try_read8_relaxed, readb_relaxed -> u8);
237    define_read!(read16_relaxed, try_read16_relaxed, readw_relaxed -> u16);
238    define_read!(read32_relaxed, try_read32_relaxed, readl_relaxed -> u32);
239    define_read!(
240        #[cfg(CONFIG_64BIT)]
241        read64_relaxed,
242        try_read64_relaxed,
243        readq_relaxed -> u64
244    );
245
246    define_write!(write8, try_write8, writeb <- u8);
247    define_write!(write16, try_write16, writew <- u16);
248    define_write!(write32, try_write32, writel <- u32);
249    define_write!(
250        #[cfg(CONFIG_64BIT)]
251        write64,
252        try_write64,
253        writeq <- u64
254    );
255
256    define_write!(write8_relaxed, try_write8_relaxed, writeb_relaxed <- u8);
257    define_write!(write16_relaxed, try_write16_relaxed, writew_relaxed <- u16);
258    define_write!(write32_relaxed, try_write32_relaxed, writel_relaxed <- u32);
259    define_write!(
260        #[cfg(CONFIG_64BIT)]
261        write64_relaxed,
262        try_write64_relaxed,
263        writeq_relaxed <- u64
264    );
265}