Introduce a buffer object type (KernelBo) for internal driver allocations that are managed by the kernel rather than userspace.
KernelBo wraps a GEM shmem object and automatically handles GPU virtual address space mapping during creation and unmapping on drop. This provides a safe and convenient way for the driver to both allocate and clean up internal buffers for kernel-managed resources. Co-developed-by: Boris Brezillon <[email protected]> Signed-off-by: Boris Brezillon <[email protected]> Signed-off-by: Deborah Brouwer <[email protected]> --- drivers/gpu/drm/tyr/gem.rs | 101 +++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 97 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/tyr/gem.rs b/drivers/gpu/drm/tyr/gem.rs index c28be61a01bb..47a05a33388e 100644 --- a/drivers/gpu/drm/tyr/gem.rs +++ b/drivers/gpu/drm/tyr/gem.rs @@ -4,18 +4,29 @@ //! This module provides buffer object (BO) management functionality using //! DRM's GEM subsystem with shmem backing. +use core::ops::Range; + use kernel::{ drm::gem::{ self, shmem, // }, prelude::*, - sync::aref::ARef, // + sync::{ + aref::ARef, + Arc, // + }, // }; -use crate::driver::{ - TyrDrmDevice, - TyrDrmDriver, // +use crate::{ + driver::{ + TyrDrmDevice, + TyrDrmDriver, // + }, + vm::{ + Vm, + VmMapFlags, // + }, }; /// Tyr's DriverObject type for GEM objects. @@ -56,3 +67,85 @@ pub(crate) fn new_dummy_object(ddev: &TyrDrmDevice) -> Result<ARef<Bo>> { Ok(bo) } + +/// Specifies how to choose a GPU virtual address for a [`KernelBo`]. +/// An automatic VA allocation strategy will be added in the future. +pub(crate) enum KernelBoVaAlloc { + /// Explicit VA address specified by the caller. + #[expect(dead_code)] + Explicit(u64), +} + +/// A kernel-owned buffer object with automatic GPU virtual address mapping. +/// +/// This structure represents a buffer object that is created and managed entirely +/// by the kernel driver, as opposed to userspace-created GEM objects. It combines +/// a GEM object with automatic GPU virtual address (VA) space mapping and cleanup. +/// +/// When dropped, the buffer is automatically unmapped from the GPU VA space. +pub(crate) struct KernelBo<'bound> { + /// The underlying GEM buffer object. + #[expect(dead_code)] + pub(crate) bo: ARef<Bo>, + /// The GPU VM this buffer is mapped into. + vm: Arc<Vm<'bound>>, + /// The GPU VA range occupied by this buffer. + va_range: Range<u64>, +} + +impl<'bound> KernelBo<'bound> { + /// Creates a new kernel-owned buffer object and maps it into GPU VA space. + /// + /// This function allocates a new shmem-backed GEM object and immediately maps + /// it into the specified GPU virtual memory space. The mapping is automatically + /// cleaned up when the [`KernelBo`] is dropped. + #[expect(dead_code)] + pub(crate) fn new( + ddev: &TyrDrmDevice, + vm: Arc<Vm<'bound>>, + size: u64, + va_alloc: KernelBoVaAlloc, + flags: VmMapFlags, + ) -> Result<Self> { + if size == 0 { + pr_err!("Cannot create KernelBo with size 0\n"); + return Err(EINVAL); + } + + let KernelBoVaAlloc::Explicit(va) = va_alloc; + + let bo = Bo::new( + ddev, + size as usize, + shmem::ObjectConfig { + map_wc: true, + parent_resv_obj: None, + }, + BoCreateArgs { flags: 0 }, + )?; + + vm.map_bo_range(&bo, 0, size, va, flags)?; + + Ok(KernelBo { + bo, + vm, + va_range: va..(va + size), + }) + } +} + +impl Drop for KernelBo<'_> { + fn drop(&mut self) { + let va = self.va_range.start; + let size = self.va_range.end - self.va_range.start; + + if let Err(e) = self.vm.unmap_range(va, size) { + pr_err!( + "Failed to unmap KernelBo range {:#x}..{:#x}: {:?}\n", + self.va_range.start, + self.va_range.end, + e + ); + } + } +} -- 2.54.0
