On 3/7/23 11:25, Asahi Lina wrote:
The DRM shmem helper includes common code useful for drivers which allocate GEM objects as anonymous shmem. Add a Rust abstraction for this. Drivers can choose the raw GEM implementation or the shmem layer, depending on their needs.
Signed-off-by: Asahi Lina lina@asahilina.net
drivers/gpu/drm/Kconfig | 5 + rust/bindings/bindings_helper.h | 2 + rust/helpers.c | 67 +++++++ rust/kernel/drm/gem/mod.rs | 3 + rust/kernel/drm/gem/shmem.rs | 381 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 458 insertions(+)
[...]
+unsafe extern "C" fn gem_create_object<T: DriverObject>(
- raw_dev: *mut bindings::drm_device,
- size: usize,
+) -> *mut bindings::drm_gem_object {
- // SAFETY: GEM ensures the device lives as long as its objects live,
- // so we can conjure up a reference from thin air and never drop it.
- let dev = ManuallyDrop::new(unsafe { device::Device::from_raw(raw_dev) });
- let inner = match T::new(&*dev, size) {
Ok(v) => v,Err(e) => return e.to_ptr(),- };
- let p = unsafe {
bindings::krealloc(core::ptr::null(),Object::<T>::SIZE,bindings::GFP_KERNEL | bindings::__GFP_ZERO,) as *mut Object<T>- };
- if p.is_null() {
return ENOMEM.to_ptr();- }
- // SAFETY: p is valid as long as the alloc succeeded
- unsafe {
addr_of_mut!((*p).dev).write(dev);addr_of_mut!((*p).inner).write(inner);- }
- // SAFETY: drm_gem_shmem_object is safe to zero-init, and
- // the rest of Object has been initialized
- let new: &mut Object<T> = unsafe { &mut *(p as *mut _) };
- new.obj.base.funcs = &Object::<T>::VTABLE;
- &mut new.obj.base
+}
It would be nice to allow to set wc inside the gem_create_object callback, as some drivers do it so, like v3d, vc4, panfrost, lima...
Best Regards, - Maíra Canal
+unsafe extern "C" fn free_callback<T: DriverObject>(obj: *mut bindings::drm_gem_object) {
- // SAFETY: All of our objects are Object<T>.
- let p = crate::container_of!(obj, Object<T>, obj) as *mut Object<T>;
- // SAFETY: p is never used after this
- unsafe {
core::ptr::drop_in_place(&mut (*p).inner);- }
- // SAFETY: This pointer has to be valid, since p is valid
- unsafe {
bindings::drm_gem_shmem_free(&mut (*p).obj);- }
+}
+impl<T: DriverObject> Object<T> {
- /// The size of this object's structure.
- const SIZE: usize = mem::size_of::<Self>();
- /// `drm_gem_object_funcs` vtable suitable for GEM shmem objects.
- const VTABLE: bindings::drm_gem_object_funcs = bindings::drm_gem_object_funcs {
free: Some(free_callback::<T>),open: Some(super::open_callback::<T, Object<T>>),close: Some(super::close_callback::<T, Object<T>>),print_info: Some(bindings::drm_gem_shmem_object_print_info),export: None,pin: Some(bindings::drm_gem_shmem_object_pin),unpin: Some(bindings::drm_gem_shmem_object_unpin),get_sg_table: Some(bindings::drm_gem_shmem_object_get_sg_table),vmap: Some(bindings::drm_gem_shmem_object_vmap),vunmap: Some(bindings::drm_gem_shmem_object_vunmap),mmap: Some(bindings::drm_gem_shmem_object_mmap),vm_ops: &SHMEM_VM_OPS,- };
- // SAFETY: Must only be used with DRM functions that are thread-safe
- unsafe fn mut_shmem(&self) -> *mut bindings::drm_gem_shmem_object {
&self.obj as *const _ as *mut _- }
- /// Create a new shmem-backed DRM object of the given size.
- pub fn new(dev: &device::Device<T::Driver>, size: usize) -> Result<gem::UniqueObjectRef<Self>> {
// SAFETY: This function can be called as long as the ALLOC_OPS are set properly// for this driver, and the gem_create_object is called.let p = unsafe { bindings::drm_gem_shmem_create(dev.raw() as *mut _, size) };let p = crate::container_of!(p, Object<T>, obj) as *mut _;// SAFETY: The gem_create_object callback ensures this is a valid Object<T>,// so we can take a unique reference to it.let obj_ref = gem::UniqueObjectRef { ptr: p };Ok(obj_ref)- }
- /// Returns the `Device` that owns this GEM object.
- pub fn dev(&self) -> &device::Device<T::Driver> {
&self.dev- }
- /// Creates (if necessary) and returns a scatter-gather table of DMA pages for this object.
- ///
- /// This will pin the object in memory.
- pub fn sg_table(&self) -> Result<SGTable<T>> {
// SAFETY: drm_gem_shmem_get_pages_sgt is thread-safe.let sgt = from_kernel_err_ptr(unsafe {bindings::drm_gem_shmem_get_pages_sgt(self.mut_shmem())})?;Ok(SGTable {sgt,_owner: self.reference(),})- }
- /// Creates and returns a virtual kernel memory mapping for this object.
- pub fn vmap(&self) -> Result<VMap<T>> {
let mut map: MaybeUninit<bindings::iosys_map> = MaybeUninit::uninit();// SAFETY: drm_gem_shmem_vmap is thread-safeto_result(unsafe { bindings::drm_gem_shmem_vmap(self.mut_shmem(), map.as_mut_ptr()) })?;// SAFETY: if drm_gem_shmem_vmap did not fail, map is initialized nowlet map = unsafe { map.assume_init() };Ok(VMap {map,owner: self.reference(),})- }
- /// Set the write-combine flag for this object.
- ///
- /// Should be called before any mappings are made.
- pub fn set_wc(&mut self, map_wc: bool) {
unsafe { (*self.mut_shmem()).map_wc = map_wc };- }
+}
+impl<T: DriverObject> Deref for Object<T> {
- type Target = T;
- fn deref(&self) -> &Self::Target {
&self.inner- }
+}
+impl<T: DriverObject> DerefMut for Object<T> {
- fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.inner- }
+}
+impl<T: DriverObject> crate::private::Sealed for Object<T> {}
+impl<T: DriverObject> gem::IntoGEMObject for Object<T> {
- type Driver = T::Driver;
- fn gem_obj(&self) -> *mut bindings::drm_gem_object {
&self.obj.base as *const _ as *mut _- }
- fn from_gem_obj(obj: *mut bindings::drm_gem_object) -> *mut Object<T> {
crate::container_of!(obj, Object<T>, obj) as *mut Object<T>- }
+}
+impl<T: DriverObject> drv::AllocImpl for Object<T> {
- const ALLOC_OPS: drv::AllocOps = drv::AllocOps {
gem_create_object: Some(gem_create_object::<T>),prime_handle_to_fd: Some(bindings::drm_gem_prime_handle_to_fd),prime_fd_to_handle: Some(bindings::drm_gem_prime_fd_to_handle),gem_prime_import: None,gem_prime_import_sg_table: Some(bindings::drm_gem_shmem_prime_import_sg_table),gem_prime_mmap: Some(bindings::drm_gem_prime_mmap),dumb_create: Some(bindings::drm_gem_shmem_dumb_create),dumb_map_offset: None,dumb_destroy: None,- };
+}
+/// A virtual mapping for a shmem-backed GEM object in kernel address space. +pub struct VMap<T: DriverObject> {
- map: bindings::iosys_map,
- owner: gem::ObjectRef<Object<T>>,
+}
+impl<T: DriverObject> VMap<T> {
- /// Returns a const raw pointer to the start of the mapping.
- pub fn as_ptr(&self) -> *const core::ffi::c_void {
// SAFETY: The shmem helpers always return non-iomem mapsunsafe { self.map.__bindgen_anon_1.vaddr }- }
- /// Returns a mutable raw pointer to the start of the mapping.
- pub fn as_mut_ptr(&mut self) -> *mut core::ffi::c_void {
// SAFETY: The shmem helpers always return non-iomem mapsunsafe { self.map.__bindgen_anon_1.vaddr }- }
- /// Returns a byte slice view of the mapping.
- pub fn as_slice(&self) -> &[u8] {
// SAFETY: The vmap maps valid memory up to the owner sizeunsafe { slice::from_raw_parts(self.as_ptr() as *const u8, self.owner.size()) }- }
- /// Returns mutable a byte slice view of the mapping.
- pub fn as_mut_slice(&mut self) -> &mut [u8] {
// SAFETY: The vmap maps valid memory up to the owner sizeunsafe { slice::from_raw_parts_mut(self.as_mut_ptr() as *mut u8, self.owner.size()) }- }
- /// Borrows a reference to the object that owns this virtual mapping.
- pub fn owner(&self) -> &gem::ObjectRef<Object<T>> {
&self.owner- }
+}
+impl<T: DriverObject> Drop for VMap<T> {
- fn drop(&mut self) {
// SAFETY: This function is thread-safeunsafe {bindings::drm_gem_shmem_vunmap(self.owner.mut_shmem(), &mut self.map);}- }
+}
+/// SAFETY: `iosys_map` objects are safe to send across threads. +unsafe impl<T: DriverObject> Send for VMap<T> {} +unsafe impl<T: DriverObject> Sync for VMap<T> {}
+/// A single scatter-gather entry, representing a span of pages in the device's DMA address space. +/// +/// For devices not behind a standalone IOMMU, this corresponds to physical addresses. +#[repr(transparent)] +pub struct SGEntry(bindings::scatterlist);
+impl SGEntry {
- /// Returns the starting DMA address of this span
- pub fn dma_address(&self) -> usize {
(unsafe { bindings::sg_dma_address(&self.0) }) as usize- }
- /// Returns the length of this span in bytes
- pub fn dma_len(&self) -> usize {
(unsafe { bindings::sg_dma_len(&self.0) }) as usize- }
+}
+/// A scatter-gather table of DMA address spans for a GEM shmem object. +/// +/// # Invariants +/// `sgt` must be a valid pointer to the `sg_table`, which must correspond to the owned +/// object in `_owner` (which ensures it remains valid). +pub struct SGTable<T: DriverObject> {
- sgt: *const bindings::sg_table,
- _owner: gem::ObjectRef<Object<T>>,
+}
+impl<T: DriverObject> SGTable<T> {
- /// Returns an iterator through the SGTable's entries
- pub fn iter(&'_ self) -> SGTableIter<'_> {
SGTableIter {left: unsafe { (*self.sgt).nents } as usize,sg: unsafe { (*self.sgt).sgl },_p: PhantomData,}- }
+}
+impl<'a, T: DriverObject> IntoIterator for &'a SGTable<T> {
- type Item = &'a SGEntry;
- type IntoIter = SGTableIter<'a>;
- fn into_iter(self) -> Self::IntoIter {
self.iter()- }
+}
+/// SAFETY: `sg_table` objects are safe to send across threads. +unsafe impl<T: DriverObject> Send for SGTable<T> {} +unsafe impl<T: DriverObject> Sync for SGTable<T> {}
+/// An iterator through `SGTable` entries. +/// +/// # Invariants +/// `sg` must be a valid pointer to the scatterlist, which must outlive our lifetime. +pub struct SGTableIter<'a> {
- sg: *mut bindings::scatterlist,
- left: usize,
- _p: PhantomData<&'a ()>,
+}
+impl<'a> Iterator for SGTableIter<'a> {
- type Item = &'a SGEntry;
- fn next(&mut self) -> OptionSelf::Item {
if self.left == 0 {None} else {let sg = self.sg;self.sg = unsafe { bindings::sg_next(self.sg) };self.left -= 1;Some(unsafe { &(*(sg as *const SGEntry)) })}- }
+}