path: root/rust/kernel/drm/device.rs

// SPDX-License-Identifier: GPL-2.0 OR MIT

//! DRM device.
//!
//! C header: [`include/drm/drm_device.h`](srctree/include/drm/drm_device.h)

use crate::{
    alloc::allocator::Kmalloc,
    bindings,
    device,
    drm::{
        self,
        driver::AllocImpl,
        private::Sealed, //
    },
    error::from_err_ptr,
    prelude::*,
    sync::aref::{
        ARef,
        AlwaysRefCounted, //
    },
    types::{
        NotThreadSafe,
        Opaque, //
    },
    workqueue::{
        HasDelayedWork,
        HasWork,
        Work,
        WorkItem, //
    }, //
};
use core::{
    alloc::Layout,
    marker::PhantomData,
    mem,
    ops::Deref,
    ptr::{
        self,
        NonNull, //
    },
};

#[cfg(CONFIG_DRM_LEGACY)]
macro_rules! drm_legacy_fields {
    ( $($field:ident: $val:expr),* $(,)? ) => {
        bindings::drm_driver {
            $( $field: $val ),*,
            firstopen: None,
            preclose: None,
            dma_ioctl: None,
            dma_quiescent: None,
            context_dtor: None,
            irq_handler: None,
            irq_preinstall: None,
            irq_postinstall: None,
            irq_uninstall: None,
            get_vblank_counter: None,
            enable_vblank: None,
            disable_vblank: None,
            dev_priv_size: 0,
        }
    }
}

#[cfg(not(CONFIG_DRM_LEGACY))]
macro_rules! drm_legacy_fields {
    ( $($field:ident: $val:expr),* $(,)? ) => {
        bindings::drm_driver {
            $( $field: $val ),*
        }
    }
}

/// A trait implemented by all possible contexts a [`Device`] can be used in.
///
/// Setting up a new [`Device`] is a multi-stage process. Each step of the process that a user
/// interacts with in Rust has a respective [`DeviceContext`] typestate. For example,
/// `Device<T, Registered>` would be a [`Device`] that reached the [`Registered`] [`DeviceContext`].
///
/// Each stage of this process is described below:
///
/// ```text
///        1                     2                         3
/// +--------------+   +------------------+   +-----------------------+
/// |Device created| → |Device initialized| → |Registered w/ userspace|
/// +--------------+   +------------------+   +-----------------------+
///    (Uninit)                                      (Registered)
/// ```
///
/// 1. The [`Device`] is in the [`Uninit`] context and is not guaranteed to be initialized or
///    registered with userspace. Only a limited subset of DRM core functionality is available.
/// 2. The [`Device`] is guaranteed to be fully initialized, but is not guaranteed to be registered
///    with userspace. All DRM core functionality which doesn't interact with userspace is
///    available. We currently don't have a context for representing this.
/// 3. The [`Device`] is guaranteed to be fully initialized, and is guaranteed to have been
///    registered with userspace at some point - thus putting it in the [`Registered`] context.
///
/// An important caveat of [`DeviceContext`] which must be kept in mind: when used as a typestate
/// for a reference type, it can only guarantee that a [`Device`] reached a particular stage in the
/// initialization process _at the time the reference was taken_. No guarantee is made in regards to
/// what stage of the process the [`Device`] is currently in. This means for instance that a
/// `&Device<T, Uninit>` may actually be registered with userspace, it just wasn't known to be
/// registered at the time the reference was taken.
pub trait DeviceContext: Sealed + Send + Sync {}

/// The [`DeviceContext`] of a [`Device`] that was registered with userspace at some point.
///
/// This represents a [`Device`] which is guaranteed to have been registered with userspace at
/// some point in time. Such a DRM device is guaranteed to have been fully-initialized.
///
/// Note: A device in this context is not guaranteed to remain registered with userspace for its
/// entire lifetime, as this is impossible to guarantee at compile-time.
///
/// # Invariants
///
/// A [`Device`] in this [`DeviceContext`] is guaranteed to have been registered with userspace
/// at some point in time.
pub struct Registered;

impl Sealed for Registered {}
impl DeviceContext for Registered {}

/// The [`DeviceContext`] of a [`Device`] that may be unregistered and partly uninitialized.
///
/// A [`Device`] in this context is only guaranteed to be partly initialized, and may or may not
/// be registered with userspace. Thus operations which depend on the [`Device`] being fully
/// initialized, or which depend on the [`Device`] being registered with userspace are not
/// available through this [`DeviceContext`].
///
/// A [`Device`] in this context can be used to create a
/// [`Registration`](drm::driver::Registration).
pub struct Uninit;

impl Sealed for Uninit {}
impl DeviceContext for Uninit {}

/// A [`Device`] which is known at compile-time to be unregistered with userspace.
///
/// This type allows performing operations which are only safe to do before userspace registration,
/// and can be used to create a [`Registration`](drm::driver::Registration) once the driver is ready
/// to register the device with userspace.
///
/// Since DRM device initialization must be single-threaded, this object is not thread-safe.
///
/// # Invariants
///
/// The device in `self.0` is guaranteed to be a newly created [`Device`] that has not yet been
/// registered with userspace until this type is dropped.
pub struct UnregisteredDevice<T: drm::Driver>(ARef<Device<T, Uninit>>, NotThreadSafe);

impl<T: drm::Driver> Deref for UnregisteredDevice<T> {
    type Target = Device<T, Uninit>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl<T: drm::Driver> UnregisteredDevice<T> {
    const fn compute_features() -> u32 {
        let mut features = drm::driver::FEAT_GEM;

        if T::FEAT_RENDER {
            features |= drm::driver::FEAT_RENDER;
        }

        features
    }

    const VTABLE: bindings::drm_driver = drm_legacy_fields! {
        load: None,
        open: Some(drm::File::<T::File>::open_callback),
        postclose: Some(drm::File::<T::File>::postclose_callback),
        unload: None,
        release: Some(Device::<T>::release),
        master_set: None,
        master_drop: None,
        debugfs_init: None,

        // Ignore the Uninit DeviceContext below. It is only provided because it is required by the
        // compiler, and it is not actually used by these functions.
        gem_create_object: T::Object::<Uninit>::ALLOC_OPS.gem_create_object,
        prime_handle_to_fd: T::Object::<Uninit>::ALLOC_OPS.prime_handle_to_fd,
        prime_fd_to_handle: T::Object::<Uninit>::ALLOC_OPS.prime_fd_to_handle,
        gem_prime_import: T::Object::<Uninit>::ALLOC_OPS.gem_prime_import,
        gem_prime_import_sg_table: T::Object::<Uninit>::ALLOC_OPS.gem_prime_import_sg_table,
        dumb_create: T::Object::<Uninit>::ALLOC_OPS.dumb_create,
        dumb_map_offset: T::Object::<Uninit>::ALLOC_OPS.dumb_map_offset,

        show_fdinfo: None,
        fbdev_probe: None,

        major: T::INFO.major,
        minor: T::INFO.minor,
        patchlevel: T::INFO.patchlevel,
        name: crate::str::as_char_ptr_in_const_context(T::INFO.name).cast_mut(),
        desc: crate::str::as_char_ptr_in_const_context(T::INFO.desc).cast_mut(),

        driver_features: Self::compute_features(),
        ioctls: T::IOCTLS.as_ptr(),
        num_ioctls: T::IOCTLS.len() as i32,
        fops: &Self::GEM_FOPS,
    };

    const GEM_FOPS: bindings::file_operations = drm::gem::create_fops();

    /// Create a new `UnregisteredDevice` for a `drm::Driver`.
    ///
    /// This can be used to create a [`Registration`](kernel::drm::Registration).
    pub fn new(dev: &device::Device, data: impl PinInit<T::Data, Error>) -> Result<Self> {
        // `__drm_dev_alloc` uses `kmalloc()` to allocate memory, hence ensure a `kmalloc()`
        // compatible `Layout`.
        let layout = Kmalloc::aligned_layout(Layout::new::<Device<T, Uninit>>());

        // Use a temporary vtable without a `release` callback until `data` is initialized, so
        // init failure can release the DRM device without dropping uninitialized fields.
        let alloc_vtable = bindings::drm_driver {
            release: None,
            ..Self::VTABLE
        };

        // SAFETY:
        // - `alloc_vtable` reference remains valid until no longer used,
        // - `dev` is valid by its type invarants,
        let raw_drm: *mut Device<T, Uninit> = unsafe {
            bindings::__drm_dev_alloc(
                dev.as_raw(),
                &alloc_vtable,
                layout.size(),
                mem::offset_of!(Device<T, Uninit>, dev),
            )
        }
        .cast();
        let raw_drm = NonNull::new(from_err_ptr(raw_drm)?).ok_or(ENOMEM)?;

        // SAFETY: `raw_drm` is a valid pointer to `Self`, given that `__drm_dev_alloc` was
        // successful.
        let drm_dev = unsafe { Device::into_drm_device(raw_drm) };

        // SAFETY: `raw_drm` is a valid pointer to `Self`.
        let raw_data = unsafe { ptr::addr_of_mut!((*raw_drm.as_ptr()).data) };

        // SAFETY:
        // - `raw_data` is a valid pointer to uninitialized memory.
        // - `raw_data` will not move until it is dropped.
        unsafe { data.__pinned_init(raw_data) }.inspect_err(|_| {
            // SAFETY: `__drm_dev_alloc()` was successful, hence `drm_dev` must be valid and the
            // refcount must be non-zero.
            unsafe { bindings::drm_dev_put(drm_dev) };
        })?;

        // SAFETY: `drm_dev` is still private to this function.
        unsafe { (*drm_dev).driver = const { &Self::VTABLE } };

        // SAFETY: The reference count is one, and now we take ownership of that reference as a
        // `drm::Device`.
        // INVARIANT: We just created the device above, but have yet to call `drm_dev_register`.
        // `Self` cannot be copied or sent to another thread - ensuring that `drm_dev_register`
        // won't be called during its lifetime and that the device is unregistered.
        Ok(Self(unsafe { ARef::from_raw(raw_drm) }, NotThreadSafe))
    }
}

/// A typed DRM device with a specific [`drm::Driver`] implementation and [`DeviceContext`].
///
/// Since DRM devices can be used before being ful