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};
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    fn as_raw(&self) -> *mut bindings::firmware {
90        self.0.as_ptr()
91    }
92
93    /// Returns the size of the requested firmware in bytes.
94    pub fn size(&self) -> usize {
95        // SAFETY: `self.as_raw()` is valid by the type invariant.
96        unsafe { (*self.as_raw()).size }
97    }
98
99    /// Returns the requested firmware as `&[u8]`.
100    pub fn data(&self) -> &[u8] {
101        // SAFETY: `self.as_raw()` is valid by the type invariant. Additionally,
102        // `bindings::firmware` guarantees, if successfully requested, that
103        // `bindings::firmware::data` has a size of `bindings::firmware::size` bytes.
104        unsafe { core::slice::from_raw_parts((*self.as_raw()).data, self.size()) }
105    }
106}
107
108impl Drop for Firmware {
109    fn drop(&mut self) {
110        // SAFETY: `self.as_raw()` is valid by the type invariant.
111        unsafe { bindings::release_firmware(self.as_raw()) };
112    }
113}
114
115// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, which is safe to be used from
116// any thread.
117unsafe impl Send for Firmware {}
118
119// SAFETY: `Firmware` only holds a pointer to a C `struct firmware`, references to which are safe to
120// be used from any thread.
121unsafe impl Sync for Firmware {}
122
123/// Create firmware .modinfo entries.
124///
125/// This macro is the counterpart of the C macro `MODULE_FIRMWARE()`, but instead of taking a
126/// simple string literals, which is already covered by the `firmware` field of
127/// [`crate::prelude::module!`], it allows the caller to pass a builder type, based on the
128/// [`ModInfoBuilder`], which can create the firmware modinfo strings in a more flexible way.
129///
130/// Drivers should extend the [`ModInfoBuilder`] with their own driver specific builder type.
131///
132/// The `builder` argument must be a type which implements the following function.
133///
134/// `const fn create(module_name: &'static CStr) -> ModInfoBuilder`
135///
136/// `create` should pass the `module_name` to the [`ModInfoBuilder`] and, with the help of
137/// it construct the corresponding firmware modinfo.
138///
139/// Typically, such contracts would be enforced by a trait, however traits do not (yet) support
140/// const functions.
141///
142/// # Example
143///
144/// ```
145/// # mod module_firmware_test {
146/// # use kernel::firmware;
147/// # use kernel::prelude::*;
148/// #
149/// # struct MyModule;
150/// #
151/// # impl kernel::Module for MyModule {
152/// #     fn init(_module: &'static ThisModule) -> Result<Self> {
153/// #         Ok(Self)
154/// #     }
155/// # }
156/// #
157/// #
158/// struct Builder<const N: usize>;
159///
160/// impl<const N: usize> Builder<N> {
161///     const DIR: &'static str = "vendor/chip/";
162///     const FILES: [&'static str; 3] = [ "foo", "bar", "baz" ];
163///
164///     const fn create(module_name: &'static kernel::str::CStr) -> firmware::ModInfoBuilder<N> {
165///         let mut builder = firmware::ModInfoBuilder::new(module_name);
166///
167///         let mut i = 0;
168///         while i < Self::FILES.len() {
169///             builder = builder.new_entry()
170///                 .push(Self::DIR)
171///                 .push(Self::FILES[i])
172///                 .push(".bin");
173///
174///                 i += 1;
175///         }
176///
177///         builder
178///      }
179/// }
180///
181/// module! {
182///    type: MyModule,
183///    name: "module_firmware_test",
184///    author: "Rust for Linux",
185///    description: "module_firmware! test module",
186///    license: "GPL",
187/// }
188///
189/// kernel::module_firmware!(Builder);
190/// # }
191/// ```
192#[macro_export]
193macro_rules! module_firmware {
194    // The argument is the builder type without the const generic, since it's deferred from within
195    // this macro. Hence, we can neither use `expr` nor `ty`.
196    ($($builder:tt)*) => {
197        const _: () = {
198            const __MODULE_FIRMWARE_PREFIX: &'static $crate::str::CStr = if cfg!(MODULE) {
199                $crate::c_str!("")
200            } else {
201                <LocalModule as $crate::ModuleMetadata>::NAME
202            };
203
204            #[link_section = ".modinfo"]
205            #[used]
206            static __MODULE_FIRMWARE: [u8; $($builder)*::create(__MODULE_FIRMWARE_PREFIX)
207                .build_length()] = $($builder)*::create(__MODULE_FIRMWARE_PREFIX).build();
208        };
209    };
210}
211
212/// Builder for firmware module info.
213///
214/// [`ModInfoBuilder`] is a helper component to flexibly compose firmware paths strings for the
215/// .modinfo section in const context.
216///
217/// Therefore the [`ModInfoBuilder`] provides the methods [`ModInfoBuilder::new_entry`] and
218/// [`ModInfoBuilder::push`], where the latter is used to push path components and the former to
219/// mark the beginning of a new path string.
220///
221/// [`ModInfoBuilder`] is meant to be used in combination with [`kernel::module_firmware!`].
222///
223/// The const generic `N` as well as the `module_name` parameter of [`ModInfoBuilder::new`] is an
224/// internal implementation detail and supplied through the above macro.
225pub struct ModInfoBuilder<const N: usize> {
226    buf: [u8; N],
227    n: usize,
228    module_name: &'static CStr,
229}
230
231impl<const N: usize> ModInfoBuilder<N> {
232    /// Create an empty builder instance.
233    pub const fn new(module_name: &'static CStr) -> Self {
234        Self {
235            buf: [0; N],
236            n: 0,
237            module_name,
238        }
239    }
240
241    const fn push_internal(mut self, bytes: &[u8]) -> Self {
242        let mut j = 0;
243
244        if N == 0 {
245            self.n += bytes.len();
246            return self;
247        }
248
249        while j < bytes.len() {
250            if self.n < N {
251                self.buf[self.n] = bytes[j];
252            }
253            self.n += 1;
254            j += 1;
255        }
256        self
257    }
258
259    /// Push an additional path component.
260    ///
261    /// Append path components to the [`ModInfoBuilder`] instance. Paths need to be separated
262    /// with [`ModInfoBuilder::new_entry`].
263    ///
264    /// # Example
265    ///
266    /// ```
267    /// use kernel::firmware::ModInfoBuilder;
268    ///
269    /// # const DIR: &str = "vendor/chip/";
270    /// # const fn no_run<const N: usize>(builder: ModInfoBuilder<N>) {
271    /// let builder = builder.new_entry()
272    ///     .push(DIR)
273    ///     .push("foo.bin")
274    ///     .new_entry()
275    ///     .push(DIR)
276    ///     .push("bar.bin");
277    /// # }
278    /// ```
279    pub const fn push(self, s: &str) -> Self {
280        // Check whether there has been an initial call to `next_entry()`.
281        if N != 0 && self.n == 0 {
282            crate::build_error!("Must call next_entry() before push().");
283        }
284
285        self.push_internal(s.as_bytes())
286    }
287
288    const fn push_module_name(self) -> Self {
289        let mut this = self;
290        let module_name = this.module_name;
291
292        if !this.module_name.is_empty() {
293            this = this.push_internal(module_name.as_bytes_with_nul());
294
295            if N != 0 {
296                // Re-use the space taken by the NULL terminator and swap it with the '.' separator.
297                this.buf[this.n - 1] = b'.';
298            }
299        }
300
301        this
302    }
303
304    /// Prepare the [`ModInfoBuilder`] for the next entry.
305    ///
306    /// This method acts as a separator between module firmware path entries.
307    ///
308    /// Must be called before constructing a new entry with subsequent calls to
309    /// [`ModInfoBuilder::push`].
310    ///
311    /// See [`ModInfoBuilder::push`] for an example.
312    pub const fn new_entry(self) -> Self {
313        self.push_internal(b"\0")
314            .push_module_name()
315            .push_internal(b"firmware=")
316    }
317
318    /// Build the byte array.
319    pub const fn build(self) -> [u8; N] {
320        // Add the final NULL terminator.
321        let this = self.push_internal(b"\0");
322
323        if this.n == N {
324            this.buf
325        } else {
326            crate::build_error!("Length mismatch.");
327        }
328    }
329}
330
331impl ModInfoBuilder<0> {
332    /// Return the length of the byte array to build.
333    pub const fn build_length(self) -> usize {
334        // Compensate for the NULL terminator added by `build`.
335        self.n + 1
336    }
337}
kernel/firmware.rs

kernel/
firmware.rs
