kernel/drm/gem/
mod.rs

1// SPDX-License-Identifier: GPL-2.0 OR MIT
2
3//! DRM GEM API
4//!
5//! C header: [`include/drm/drm_gem.h`](srctree/include/drm/drm_gem.h)
6
7use crate::{
8    alloc::flags::*,
9    bindings, drm,
10    drm::driver::{AllocImpl, AllocOps},
11    error::{to_result, Result},
12    prelude::*,
13    sync::aref::{ARef, AlwaysRefCounted},
14    types::Opaque,
15};
16use core::{ops::Deref, ptr::NonNull};
17
18/// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
19/// [`DriverObject`] implementation.
20///
21/// [`Driver`]: drm::Driver
22/// [`DriverFile`]: drm::file::DriverFile
23pub type DriverFile<T> = drm::File<<<T as DriverObject>::Driver as drm::Driver>::File>;
24
25/// GEM object functions, which must be implemented by drivers.
26pub trait DriverObject: Sync + Send + Sized {
27    /// Parent `Driver` for this object.
28    type Driver: drm::Driver;
29
30    /// Create a new driver data object for a GEM object of a given size.
31    fn new(dev: &drm::Device<Self::Driver>, size: usize) -> impl PinInit<Self, Error>;
32
33    /// Open a new handle to an existing object, associated with a File.
34    fn open(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) -> Result {
35        Ok(())
36    }
37
38    /// Close a handle to an existing object, associated with a File.
39    fn close(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) {}
40}
41
42/// Trait that represents a GEM object subtype
43pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
44    /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
45    /// this owning object is valid.
46    fn as_raw(&self) -> *mut bindings::drm_gem_object;
47
48    /// Converts a pointer to a `struct drm_gem_object` into a reference to `Self`.
49    ///
50    /// # Safety
51    ///
52    /// - `self_ptr` must be a valid pointer to `Self`.
53    /// - The caller promises that holding the immutable reference returned by this function does
54    ///   not violate rust's data aliasing rules and remains valid throughout the lifetime of `'a`.
55    unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self;
56}
57
58extern "C" fn open_callback<T: DriverObject>(
59    raw_obj: *mut bindings::drm_gem_object,
60    raw_file: *mut bindings::drm_file,
61) -> core::ffi::c_int {
62    // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
63    let file = unsafe { DriverFile::<T>::from_raw(raw_file) };
64
65    // SAFETY: `open_callback` is specified in the AllocOps structure for `DriverObject<T>`,
66    // ensuring that `raw_obj` is contained within a `DriverObject<T>`
67    let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj) };
68
69    match T::open(obj, file) {
70        Err(e) => e.to_errno(),
71        Ok(()) => 0,
72    }
73}
74
75extern "C" fn close_callback<T: DriverObject>(
76    raw_obj: *mut bindings::drm_gem_object,
77    raw_file: *mut bindings::drm_file,
78) {
79    // SAFETY: `open_callback` is only ever called with a valid pointer to a `struct drm_file`.
80    let file = unsafe { DriverFile::<T>::from_raw(raw_file) };
81
82    // SAFETY: `close_callback` is specified in the AllocOps structure for `Object<T>`, ensuring
83    // that `raw_obj` is indeed contained within a `Object<T>`.
84    let obj = unsafe { <<T::Driver as drm::Driver>::Object as IntoGEMObject>::from_raw(raw_obj) };
85
86    T::close(obj, file);
87}
88
89impl<T: DriverObject> IntoGEMObject for Object<T> {
90    fn as_raw(&self) -> *mut bindings::drm_gem_object {
91        self.obj.get()
92    }
93
94    unsafe fn from_raw<'a>(self_ptr: *mut bindings::drm_gem_object) -> &'a Self {
95        // SAFETY: `obj` is guaranteed to be in an `Object<T>` via the safety contract of this
96        // function
97        unsafe { &*crate::container_of!(Opaque::cast_from(self_ptr), Object<T>, obj) }
98    }
99}
100
101/// Base operations shared by all GEM object classes
102pub trait BaseObject: IntoGEMObject {
103    /// Returns the size of the object in bytes.
104    fn size(&self) -> usize {
105        // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `struct drm_gem_object`.
106        unsafe { (*self.as_raw()).size }
107    }
108
109    /// Creates a new handle for the object associated with a given `File`
110    /// (or returns an existing one).
111    fn create_handle<D, F>(&self, file: &drm::File<F>) -> Result<u32>
112    where
113        Self: AllocImpl<Driver = D>,
114        D: drm::Driver<Object = Self, File = F>,
115        F: drm::file::DriverFile<Driver = D>,
116    {
117        let mut handle: u32 = 0;
118        // SAFETY: The arguments are all valid per the type invariants.
119        to_result(unsafe {
120            bindings::drm_gem_handle_create(file.as_raw().cast(), self.as_raw(), &mut handle)
121        })?;
122        Ok(handle)
123    }
124
125    /// Looks up an object by its handle for a given `File`.
126    fn lookup_handle<D, F>(file: &drm::File<F>, handle: u32) -> Result<ARef<Self>>
127    where
128        Self: AllocImpl<Driver = D>,
129        D: drm::Driver<Object = Self, File = F>,
130        F: drm::file::DriverFile<Driver = D>,
131    {
132        // SAFETY: The arguments are all valid per the type invariants.
133        let ptr = unsafe { bindings::drm_gem_object_lookup(file.as_raw().cast(), handle) };
134        if ptr.is_null() {
135            return Err(ENOENT);
136        }
137
138        // SAFETY:
139        // - A `drm::Driver` can only have a single `File` implementation.
140        // - `file` uses the same `drm::Driver` as `Self`.
141        // - Therefore, we're guaranteed that `ptr` must be a gem object embedded within `Self`.
142        // - And we check if the pointer is null befoe calling from_raw(), ensuring that `ptr` is a
143        //   valid pointer to an initialized `Self`.
144        let obj = unsafe { Self::from_raw(ptr) };
145
146        // SAFETY:
147        // - We take ownership of the reference of `drm_gem_object_lookup()`.
148        // - Our `NonNull` comes from an immutable reference, thus ensuring it is a valid pointer to
149        //   `Self`.
150        Ok(unsafe { ARef::from_raw(obj.into()) })
151    }
152
153    /// Creates an mmap offset to map the object from userspace.
154    fn create_mmap_offset(&self) -> Result<u64> {
155        // SAFETY: The arguments are valid per the type invariant.
156        to_result(unsafe { bindings::drm_gem_create_mmap_offset(self.as_raw()) })?;
157
158        // SAFETY: The arguments are valid per the type invariant.
159        Ok(unsafe { bindings::drm_vma_node_offset_addr(&raw mut (*self.as_raw()).vma_node) })
160    }
161}
162
163impl<T: IntoGEMObject> BaseObject for T {}
164
165/// A base GEM object.
166///
167/// Invariants
168///
169/// - `self.obj` is a valid instance of a `struct drm_gem_object`.
170#[repr(C)]
171#[pin_data]
172pub struct Object<T: DriverObject + Send + Sync> {
173    obj: Opaque<bindings::drm_gem_object>,
174    #[pin]
175    data: T,
176}
177
178impl<T: DriverObject> Object<T> {
179    const OBJECT_FUNCS: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
180        free: Some(Self::free_callback),
181        open: Some(open_callback::<T>),
182        close: Some(close_callback::<T>),
183        print_info: None,
184        export: None,
185        pin: None,
186        unpin: None,
187        get_sg_table: None,
188        vmap: None,
189        vunmap: None,
190        mmap: None,
191        status: None,
192        vm_ops: core::ptr::null_mut(),
193        evict: None,
194        rss: None,
195    };
196
197    /// Create a new GEM object.
198    pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
199        let obj: Pin<KBox<Self>> = KBox::pin_init(
200            try_pin_init!(Self {
201                obj: Opaque::new(bindings::drm_gem_object::default()),
202                data <- T::new(dev, size),
203            }),
204            GFP_KERNEL,
205        )?;
206
207        // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above.
208        unsafe { (*obj.as_raw()).funcs = &Self::OBJECT_FUNCS };
209
210        // SAFETY: The arguments are all valid per the type invariants.
211        to_result(unsafe { bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size) })?;
212
213        // SAFETY: We never move out of `Self`.
214        let ptr = KBox::into_raw(unsafe { Pin::into_inner_unchecked(obj) });
215
216        // SAFETY: `ptr` comes from `KBox::into_raw` and hence can't be NULL.
217        let ptr = unsafe { NonNull::new_unchecked(ptr) };
218
219        // SAFETY: We take over the initial reference count from `drm_gem_object_init()`.
220        Ok(unsafe { ARef::from_raw(ptr) })
221    }
222
223    /// Returns the `Device` that owns this GEM object.
224    pub fn dev(&self) -> &drm::Device<T::Driver> {
225        // SAFETY:
226        // - `struct drm_gem_object.dev` is initialized and valid for as long as the GEM
227        //   object lives.
228        // - The device we used for creating the gem object is passed as &drm::Device<T::Driver> to
229        //   Object::<T>::new(), so we know that `T::Driver` is the right generic parameter to use
230        //   here.
231        unsafe { drm::Device::from_raw((*self.as_raw()).dev) }
232    }
233
234    fn as_raw(&self) -> *mut bindings::drm_gem_object {
235        self.obj.get()
236    }
237
238    extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
239        let ptr: *mut Opaque<bindings::drm_gem_object> = obj.cast();
240
241        // SAFETY: All of our objects are of type `Object<T>`.
242        let this = unsafe { crate::container_of!(ptr, Self, obj) };
243
244        // SAFETY: The C code only ever calls this callback with a valid pointer to a `struct
245        // drm_gem_object`.
246        unsafe { bindings::drm_gem_object_release(obj) };
247
248        // SAFETY: All of our objects are allocated via `KBox`, and we're in the
249        // free callback which guarantees this object has zero remaining references,
250        // so we can drop it.
251        let _ = unsafe { KBox::from_raw(this) };
252    }
253}
254
255// SAFETY: Instances of `Object<T>` are always reference-counted.
256unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {
257    fn inc_ref(&self) {
258        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
259        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
260    }
261
262    unsafe fn dec_ref(obj: NonNull<Self>) {
263        // SAFETY: `obj` is a valid pointer to an `Object<T>`.
264        let obj = unsafe { obj.as_ref() };
265
266        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
267        unsafe { bindings::drm_gem_object_put(obj.as_raw()) }
268    }
269}
270
271impl<T: DriverObject> super::private::Sealed for Object<T> {}
272
273impl<T: DriverObject> Deref for Object<T> {
274    type Target = T;
275
276    fn deref(&self) -> &Self::Target {
277        &self.data
278    }
279}
280
281impl<T: DriverObject> AllocImpl for Object<T> {
282    type Driver = T::Driver;
283
284    const ALLOC_OPS: AllocOps = AllocOps {
285        gem_create_object: None,
286        prime_handle_to_fd: None,
287        prime_fd_to_handle: None,
288        gem_prime_import: None,
289        gem_prime_import_sg_table: None,
290        dumb_create: None,
291        dumb_map_offset: None,
292    };
293}
294
295pub(super) const fn create_fops() -> bindings::file_operations {
296    // SAFETY: As by the type invariant, it is safe to initialize `bindings::file_operations`
297    // zeroed.
298    let mut fops: bindings::file_operations = unsafe { core::mem::zeroed() };
299
300    fops.owner = core::ptr::null_mut();
301    fops.open = Some(bindings::drm_open);
302    fops.release = Some(bindings::drm_release);
303    fops.unlocked_ioctl = Some(bindings::drm_ioctl);
304    #[cfg(CONFIG_COMPAT)]
305    {
306        fops.compat_ioctl = Some(bindings::drm_compat_ioctl);
307    }
308    fops.poll = Some(bindings::drm_poll);
309    fops.read = Some(bindings::drm_read);
310    fops.llseek = Some(bindings::noop_llseek);
311    fops.mmap = Some(bindings::drm_gem_mmap);
312    fops.fop_flags = bindings::FOP_UNSIGNED_OFFSET;
313
314    fops
315}
kernel/drm/gem/mod.rs

kernel/drm/gem/
mod.rs
