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

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source code of linux/rust/kernel/io.rs