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

kernel/
firmware.rs
