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+//! Memory management and buffer functionality that the DRM subsystem exposes.
+//!
+//! # Summary
+//!
+//! The DRM subsystem exposes functionality for managing memory on modern GPU
+//! devices using a system called the Graphics Execution Manager (GEM). This
+//! system manages GPU buffers and exposes them to userspace using 32-bit
+//! handles. These handles are automatically reference counted in the kernel.
+//!
+//! GEM provides a small API for sharing buffers between processes. However, it
+//! does not provide any generic API for creating these. Instead, each driver
+//! provides its own method of creating these buffers. The `libgbm` library
+//! (part of the mesa project) provides a driver agnostic method of creating
+//! these buffers.
+//!
+//! There are two methods of sharing a GEM handle between processes:
+//!
+//! 1. Using `Flink` to globally publish a handle using a 32-bit 'name'. This
+//! requires either holding the DRM Master lock or having the process'
+//! [`AuthToken`](struct@crate::AuthToken) authenticated. However, any process can
+//! open these handles if they know (or even guess) the global name.
+//!
+//! 2. Converting the GEM handle into a PRIME file descriptor, and passing it
+//! like a regular one. This allows better control and security, and is the
+//! recommended method of sharing buffers.
+
+use crate::control;
+pub use drm_fourcc::{DrmFourcc, DrmModifier, DrmVendor, UnrecognizedFourcc, UnrecognizedVendor};
+
+/// A handle to a GEM buffer
+///
+/// # Notes
+///
+/// There are no guarantees that this handle is valid. It is up to the user
+/// to make sure this handle does not outlive the underlying buffer, and to
+/// prevent buffers from leaking by properly closing them after they are done.
+#[repr(transparent)]
+#[derive(Copy, Clone, Hash, PartialEq, Eq)]
+pub struct Handle(control::RawResourceHandle);
+
+// Safety: Handle is repr(transparent) over NonZeroU32
+unsafe impl bytemuck::ZeroableInOption for Handle {}
+unsafe impl bytemuck::PodInOption for Handle {}
+
+impl From<Handle> for control::RawResourceHandle {
+ fn from(handle: Handle) -> Self {
+ handle.0
+ }
+}
+
+impl From<Handle> for u32 {
+ fn from(handle: Handle) -> Self {
+ handle.0.into()
+ }
+}
+
+impl From<control::RawResourceHandle> for Handle {
+ fn from(handle: control::RawResourceHandle) -> Self {
+ Handle(handle)
+ }
+}
+
+impl std::fmt::Debug for Handle {
+ fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+ f.debug_tuple("buffer::Handle").field(&self.0).finish()
+ }
+}
+
+/// The name of a GEM buffer.
+///
+/// # Notes
+///
+/// There are no guarantees that this name is valid. It is up to the user
+/// to make sure this name does not outlive the underlying buffer, and to
+/// prevent buffers from leaking by properly closing them after they are done.
+#[repr(transparent)]
+#[derive(Copy, Clone, Hash, PartialEq, Eq)]
+pub struct Name(u32);
+
+impl From<Name> for u32 {
+ fn from(name: Name) -> u32 {
+ name.0
+ }
+}
+
+impl std::fmt::Debug for Name {
+ fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+ f.debug_tuple("buffer::Name").field(&self.0).finish()
+ }
+}
+
+/// Common functionality of all regular buffers.
+pub trait Buffer {
+ /// The width and height of the buffer.
+ fn size(&self) -> (u32, u32);
+ /// The format of the buffer.
+ fn format(&self) -> DrmFourcc;
+ /// The pitch of the buffer.
+ fn pitch(&self) -> u32;
+ /// The handle to the buffer.
+ fn handle(&self) -> Handle;
+}
+
+/// Planar buffers are buffers where each channel/plane is in its own buffer.
+///
+/// Each plane has their own handle, pitch, and offsets.
+pub trait PlanarBuffer {
+ /// The width and height of the buffer.
+ fn size(&self) -> (u32, u32);
+ /// The format of the buffer.
+ fn format(&self) -> DrmFourcc;
+ /// The modifier of the buffer.
+ fn modifier(&self) -> Option<DrmModifier>;
+ /// The pitches of the buffer.
+ fn pitches(&self) -> [u32; 4];
+ /// The handles to the buffer.
+ fn handles(&self) -> [Option<Handle>; 4];
+ /// The offsets of the buffer.
+ fn offsets(&self) -> [u32; 4];
+}