kernel/firmware.rs
1// SPDX-License-Identifier: GPL-2.0
2
3//! Firmware abstraction
4//!
5//! C header: [`include/linux/firmware.h`](srctree/include/linux/firmware.h)
6
7use crate::{bindings, device::Device, error::Error, error::Result, ffi, str::CStr, dev_err, kernel::c_str};
8use core::ptr::NonNull;
9
10/// # Invariants
11///
12/// One of the following: `bindings::request_firmware`, `bindings::firmware_request_nowarn`,
13/// `bindings::firmware_request_platform`, `bindings::request_firmware_direct`.
14struct FwFunc(
15 unsafe extern "C" fn(
16 *mut *const bindings::firmware,
17 *const ffi::c_char,
18 *mut bindings::device,
19 ) -> i32,
20);
21
22impl FwFunc {
23 fn request() -> Self {
24 Self(bindings::request_firmware)
25 }
26
27 fn request_nowarn() -> Self {
28 Self(bindings::firmware_request_nowarn)
29 }
30}
31
32/// Abstraction around a C `struct firmware`.
33///
34/// This is a simple abstraction around the C firmware API. Just like with the C API, firmware can
35/// be requested. Once requested the abstraction provides direct access to the firmware buffer as
36/// `&[u8]`. The firmware is released once [`Firmware`] is dropped.
37///
38/// # Invariants
39///
40/// The pointer is valid, and has ownership over the instance of `struct firmware`.
41///
42/// The `Firmware`'s backing buffer is not modified.
43///
44/// # Examples
45///
46/// ```no_run
47/// # use kernel::{c_str, device::Device, firmware::Firmware};
48///
49/// # fn no_run() -> Result<(), Error> {
50/// # // SAFETY: *NOT* safe, just for the example to get an `ARef<Device>` instance
51/// # let dev = unsafe { Device::get_device(core::ptr::null_mut()) };
52///
53/// let fw = Firmware::request(c_str!("path/to/firmware.bin"), &dev)?;
54/// let blob = fw.data();
55///
56/// # Ok(())
57/// # }
58/// ```
59pub struct Firmware(NonNull<bindings::firmware>);
60
61impl Firmware {
62 fn request_internal(name: &CStr, dev: &Device, func: FwFunc) -> Result<Self> {
63 let mut fw: *mut bindings::firmware = core::ptr::null_mut();
64 let pfw: *mut *mut bindings::firmware = &mut fw;
65
66 // SAFETY: `pfw` is a valid pointer to a NULL initialized `bindings::firmware` pointer.
67 // `name` and `dev` are valid as by their type invariants.
68 let ret = unsafe { func.0(pfw as _, name.as_char_ptr(), dev.as_raw()) };
69 if ret != 0 {
70 return Err(Error::from_errno(ret));
71 }
72
73 // SAFETY: `func` not bailing out with a non-zero error code, guarantees that `fw` is a
74 // valid pointer to `bindings::firmware`.
75 Ok(Firmware(unsafe { NonNull::new_unchecked(fw) }))
76 }
77
78 /// Send a firmware request and wait for it. See also `bindings::request_firmware`.
79 pub fn request(name: &CStr, dev: &Device) -> Result<Self> {
80 Self::request_internal(name, dev, FwFunc::request())
81 }
82
83 /// Send a request for an optional firmware module. See also
84 /// `bindings::firmware_request_nowarn`.
85 pub fn request_nowarn(name: &CStr, dev: &Device) -> Result<Self> {
86 Self::request_internal(name, dev, FwFunc::request_nowarn())
87 }
88
89 /// Send a request for a nonresolvable name.
90 pub fn reject_nowarn(_name: &CStr, dev: &Device) -> Result<Self> {
91 Self::request_internal(c_str!("/*(DEBLOBBED)*/"), dev, FwFunc::request_nowarn())
92 }
93
94 /// Send a request for a nonresolvable name.
95 pub fn reject(name: &CStr, dev: &Device) -> Result<Self> {
96 dev_err!(dev, "Missing Free {} (non-Free firmware loading is disabled)\n", name);
97 Self::reject_nowarn(name, dev)
98 }
99
100
101 fn as_raw(&self) -> *mut bindings::firmware {
102 self.0.as_ptr()
103 }
104
105 /// Returns the size of the requested firmware in bytes.
106 pub fn size(&self) -> usize {
107 // SAFETY: `self.as_raw()` is valid by the type invariant.
108 unsafe { (*self.as_raw()).size }
109 }
110
111 /// Returns the requested firmware as `&[u8]`.
112 pub fn data(&self) -> &[u8] {
113 // SAFETY: `self.as_raw()` is valid by the type invariant. Additionally,
114 // `bindings::firmware` guarantees, if successfully requested, that
115 // `bindings::firmware::data` has a size of `bindings::firmware::size` bytes.
116 unsafe { core::slice::from_raw_parts((*self.as_raw()).data, self.size()) }
117 }
118}
119
120impl Drop for Firmware {
121 fn drop(&mut self) {
122 // SAFETY: `self.as_raw()` is valid by the type invariant.
123 unsafe { bindings::release_firmware(self.as_raw()) };
124 }
125}
126
127// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, which is safe to be used from
128// any thread.
129unsafe impl Send for Firmware {}
130
131// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, references to which are safe to
132// be used from any thread.
133unsafe impl Sync for Firmware {}
134
135/// Create firmware .modinfo entries.
136///
137/// This macro is the counterpart of the C macro `MODULE_FIRMWARE()`, but instead of taking a
138/// simple string literals, which is already covered by the `firmware` field of
139/// [`crate::prelude::module!`], it allows the caller to pass a builder type, based on the
140/// [`ModInfoBuilder`], which can create the firmware modinfo strings in a more flexible way.
141///
142/// Drivers should extend the [`ModInfoBuilder`] with their own driver specific builder type.
143///
144/// The `builder` argument must be a type which implements the following function.
145///
146/// `const fn create(module_name: &'static CStr) -> ModInfoBuilder`
147///
148/// `create` should pass the `module_name` to the [`ModInfoBuilder`] and, with the help of
149/// it construct the corresponding firmware modinfo.
150///
151/// Typically, such contracts would be enforced by a trait, however traits do not (yet) support
152/// const functions.
153///
154/// # Example
155///
156/// ```
157/// # mod module_firmware_test {
158/// # use kernel::firmware;
159/// # use kernel::prelude::*;
160/// #
161/// # struct MyModule;
162/// #
163/// # impl kernel::Module for MyModule {
164/// # fn init(_module: &'static ThisModule) -> Result<Self> {
165/// # Ok(Self)
166/// # }
167/// # }
168/// #
169/// #
170/// struct Builder<const N: usize>;
171///
172/// impl<const N: usize> Builder<N> {
173/// const DIR: &'static str = "vendor/chip/";
174/// const FILES: [&'static str; 3] = [ "foo", "bar", "baz" ];
175///
176/// const fn create(module_name: &'static kernel::str::CStr) -> firmware::ModInfoBuilder<N> {
177/// let mut builder = firmware::ModInfoBuilder::new(module_name);
178///
179/// let mut i = 0;
180/// while i < Self::FILES.len() {
181/// builder = builder.new_entry()
182/// .push(Self::DIR)
183/// .push(Self::FILES[i])
184/// .push(".bin");
185///
186/// i += 1;
187/// }
188///
189/// builder
190/// }
191/// }
192///
193/// module! {
194/// type: MyModule,
195/// name: "module_firmware_test",
196/// author: "Rust for Linux",
197/// description: "module_firmware! test module",
198/// license: "GPL",
199/// }
200///
201/// kernel::module_firmware!(Builder);
202/// # }
203/// ```
204#[macro_export]
205macro_rules! module_firmware {
206 // The argument is the builder type without the const generic, since it's deferred from within
207 // this macro. Hence, we can neither use `expr` nor `ty`.
208 ($($builder:tt)*) => {
209 const _: () = {
210 const __MODULE_FIRMWARE_PREFIX: &'static $crate::str::CStr = if cfg!(MODULE) {
211 $crate::c_str!("")
212 } else {
213 <LocalModule as $crate::ModuleMetadata>::NAME
214 };
215
216 #[link_section = ".modinfo"]
217 #[used]
218 static __MODULE_FIRMWARE: [u8; $($builder)*::create(__MODULE_FIRMWARE_PREFIX)
219 .build_length()] = $($builder)*::create(__MODULE_FIRMWARE_PREFIX).build();
220 };
221 };
222}
223
224/// Builder for firmware module info.
225///
226/// [`ModInfoBuilder`] is a helper component to flexibly compose firmware paths strings for the
227/// .modinfo section in const context.
228///
229/// Therefore the [`ModInfoBuilder`] provides the methods [`ModInfoBuilder::new_entry`] and
230/// [`ModInfoBuilder::push`], where the latter is used to push path components and the former to
231/// mark the beginning of a new path string.
232///
233/// [`ModInfoBuilder`] is meant to be used in combination with [`kernel::module_firmware!`].
234///
235/// The const generic `N` as well as the `module_name` parameter of [`ModInfoBuilder::new`] is an
236/// internal implementation detail and supplied through the above macro.
237pub struct ModInfoBuilder<const N: usize> {
238 buf: [u8; N],
239 n: usize,
240 module_name: &'static CStr,
241}
242
243impl<const N: usize> ModInfoBuilder<N> {
244 /// Create an empty builder instance.
245 pub const fn new(module_name: &'static CStr) -> Self {
246 Self {
247 buf: [0; N],
248 n: 0,
249 module_name,
250 }
251 }
252
253 const fn push_internal(mut self, bytes: &[u8]) -> Self {
254 let mut j = 0;
255
256 if N == 0 {
257 self.n += bytes.len();
258 return self;
259 }
260
261 while j < bytes.len() {
262 if self.n < N {
263 self.buf[self.n] = bytes[j];
264 }
265 self.n += 1;
266 j += 1;
267 }
268 self
269 }
270
271 /// Push an additional path component.
272 ///
273 /// Append path components to the [`ModInfoBuilder`] instance. Paths need to be separated
274 /// with [`ModInfoBuilder::new_entry`].
275 ///
276 /// # Example
277 ///
278 /// ```
279 /// use kernel::firmware::ModInfoBuilder;
280 ///
281 /// # const DIR: &str = "vendor/chip/";
282 /// # const fn no_run<const N: usize>(builder: ModInfoBuilder<N>) {
283 /// let builder = builder.new_entry()
284 /// .push(DIR)
285 /// .push("foo.bin")
286 /// .new_entry()
287 /// .push(DIR)
288 /// .push("bar.bin");
289 /// # }
290 /// ```
291 pub const fn push(self, s: &str) -> Self {
292 // Check whether there has been an initial call to `next_entry()`.
293 if N != 0 && self.n == 0 {
294 crate::build_error!("Must call next_entry() before push().");
295 }
296
297 self.push_internal(s.as_bytes())
298 }
299
300 const fn push_module_name(self) -> Self {
301 let mut this = self;
302 let module_name = this.module_name;
303
304 if !this.module_name.is_empty() {
305 this = this.push_internal(module_name.as_bytes_with_nul());
306
307 if N != 0 {
308 // Re-use the space taken by the NULL terminator and swap it with the '.' separator.
309 this.buf[this.n - 1] = b'.';
310 }
311 }
312
313 this
314 }
315
316 /// Prepare the [`ModInfoBuilder`] for the next entry.
317 ///
318 /// This method acts as a separator between module firmware path entries.
319 ///
320 /// Must be called before constructing a new entry with subsequent calls to
321 /// [`ModInfoBuilder::push`].
322 ///
323 /// See [`ModInfoBuilder::push`] for an example.
324 pub const fn new_entry(self) -> Self {
325 self.push_internal(b"\0")
326 .push_module_name()
327 .push_internal(b"firmware=")
328 }
329
330 /// Build the byte array.
331 pub const fn build(self) -> [u8; N] {
332 // Add the final NULL terminator.
333 let this = self.push_internal(b"\0");
334
335 if this.n == N {
336 this.buf
337 } else {
338 crate::build_error!("Length mismatch.");
339 }
340 }
341}
342
343impl ModInfoBuilder<0> {
344 /// Return the length of the byte array to build.
345 pub const fn build_length(self) -> usize {
346 // Compensate for the NULL terminator added by `build`.
347 self.n + 1
348 }
349}