I/O type generalization and projection
This series presents a major rework of I/O types, as a summary:
- Make I/O regions typed. The existing untyped region still exists
with a dynamically sized `Region` type.
- Create I/O view types to represent subregion of a full I/O region mapped.
A projection macro is added to allow safely create such subviews.
- Split I/O traits, make I/O views play a central role, avoid
duplicate monomorphization and less `unsafe` code.
- Add a `SysMem` backend, and make `Coherent` implement `Io`.
- Add copying methods (memcpy_{from,to}io and friends).
This series generalize `Mmio` type from just an untyped region to typed
representations (so `MmioRaw<T>` is `__iomem *T`). This allows us to remove
the `IoKnownSize` trait; the information is sourced from just the pointer
from the `KnownSize` trait instead.
Building on top of that, `Mmio` and `ConfigSpace` have been converted to
typed views of I/O regions rather than just a big chunk of untyped I/O
memory. These changes made it possible to implement `Io` trait for
`Coherent<T>`.
Shared system memory, `SysMem` is also added to the series, given it
similarity in implementation compared to `Coherent`. In fact, the series
use `SysMem` to implement `Coherent`'s I/O methods.
Built on these generalization, this series add `io_project!()`.
`io_project!()` performs a safe way to project a bigger view to a small
subviews, and some Nova code has been converted in this series to
demonstrate cleanups possible with this addition.
New `io_read!()`, `io_write!()` has been added that supersedes
`dma_read!()`, `dma_write!()` macro. Although, they work for primitives
only (to be exact, types that the backend is `IoCapable` of).
One feature that was lost from the old `dma_read!()` and `dma_write!()`
series was the ability to read/write a large structs. However, the
semantics was unclear to begin with, as there was no guarantee about their
atomicity even for structs that were small enough to fit in u32.
Suggested-by: Danilo Krummrich <dakr@kernel.org>
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Generic.20I.2FO.20backends/near/571198078
This is a stable tag for other trees to merge.
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Moving a GpuVaAlloc or GpuVmBo between threads currently forces drivers
to write their own unsafe Send and Sync impls. Provide the markers in
the abstraction instead.
GpuVaAlloc wraps only uninitialised memory and exposes none of it.
GpuVmBo hands out the driver data and GEM object by shared reference and
drops them in its deferred put; the DriverGpuVm trait already guarantees
both are Send + Sync, so both impls are unconditional.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://patch.msgid.link/20260611-gpuvm-sync-send-v4-2-6c7f4ab2778a@google.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
DriverGpuVm permitted !Send/!Sync associated data on an abstraction whose
handles are shared and dropped across threads: obtain() runs from many
threads and the VA API performs deferred cross-thread drops. That is
unsound.
Require Send + Sync on the trait and its associated data so the GpuVm and
UniqueRefGpuVm handle impls need no per-impl bounds.
Fixes: 82b78182ea ("rust: drm: add base GPUVM immediate mode abstraction")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://patch.msgid.link/20260611-gpuvm-sync-send-v4-1-6c7f4ab2778a@google.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
IntoGEMObject::from_raw() receives a pointer to struct drm_gem_object,
not a pointer to Self. The previous documentation used Self even though
the function argument is the embedded GEM object pointer.
However, the pointer must not be any arbitrary valid drm_gem_object. The
implementations recover Self with container_of(), so the GEM object must
be embedded in a valid Self instance. This patch documents that requirement
explicitly.
Assisted-by: Codex:GPT-5
Signed-off-by: Yilin Chen <1479826151@qq.com>
Link: https://patch.msgid.link/tencent_4426892E62B77DEA2AE898E899A871940005@qq.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Pass registration data to ioctl handlers via
drm::Device<Registered>::registration_data_with(). The closure's HRTB
ties the lifetime to the closure scope, and the pointer cast shortens it
from 'static internally. The reference is valid for the duration of the
drm_dev_enter/exit critical section held by RegistrationGuard.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-19-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a RegistrationData GAT (Generic Associated Type) to drm::Driver.
The lifetime parameter is tied to the parent bus device binding scope.
Registration<'a, T> takes ownership of the data via Pin<KBox<_>>,
storing it with its real lifetime. The pointer is written to drm::Device
before drm_dev_register() to ensure it is already in place when ioctls
arrive.
Device<T, Registered>::registration_data_with() provides access with the
lifetime shortened from 'static via a pointer cast. Since
Registration::drop() calls drm_dev_unplug(), which performs an SRCU
barrier waiting for all drm_dev_enter() critical sections to complete,
the data is guaranteed to remain valid for the duration of any
RegistrationGuard.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-18-dakr@kernel.org
[ Move registration_data_unchecked() to Device<T, Registered> impl
block. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Make Ioctl handlers receive a &Device<T, Registered> reference, proving
at the type level that the device is registered and its parent bus
device is bound.
This is achieved by calling registration_guard() on the Device<T, Ioctl>
obtained in ioctl dispatch context. If the device has been unplugged,
the ioctl returns -ENODEV without calling the handler.
To resolve the driver type parameter T for type inference, which the
compiler cannot propagate through method resolution and associated-type
projections alone, a dead-code closure and a helper function are used as
a type-inference anchor.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-14-dakr@kernel.org
[ Use imperative mood in commit message; clarify __dev_ctx_cast() doc
comment to reflect Ioctl-to-Registered cast. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
DRM ioctls do not guarantee that the parent bus device is still bound.
However, since DRM device registration is managed through Devres, using
drm_dev_unplug() on unregistration ensures that between drm_dev_enter()
and drm_dev_exit() the parent device must be bound.
Add RegistrationGuard, a guard object representing a drm_dev_enter/exit
SRCU critical section that dereferences to &Device<T, Registered>. The
guard is obtained from Device<T, Ioctl> and proves at runtime that the
device is still registered.
Switch Registration::drop from drm_dev_unregister() to drm_dev_unplug()
to provide the SRCU barrier that RegistrationGuard's safety argument
relies on.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-13-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add the Ioctl DeviceContext for DRM devices that have been registered
with userspace previously.
A Device<T, Ioctl> has been registered at some point, but may be
concurrently unregistering or already unregistered. drm_dev_enter() can
guard against this, ensuring the device remains registered for the
duration of the critical section.
This typestate will be used in ioctl dispatch context where registration
is guaranteed by the DRM core, and RegistrationGuard can safely be
acquired.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-12-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Explicitly annotate the Device reference produced by from_raw() in the
ioctl dispatch macro as Device<_, Normal>. Without this annotation, the
context is inferred from the handler's first parameter type, which would
allow a handler declaring &Device<T, Registered> to obtain a Registered
reference without runtime proof via RegistrationGuard.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-11-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Now that AlwaysRefCounted is restricted to the Normal GEM Object
context, there is no use for instantiating Object<T, C> with a
non-Normal context. Remove the DeviceContext generic parameter from
shmem::Object and all associated types (VMap, VMapRef, VMapOwned,
DmaResvGuard, SGTableMap), simplifying the API.
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-9-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Restrict AlwaysRefCounted for gem::Object and gem::shmem::Object to the
Normal context, since only Normal objects should be independently
reference-counted.
To avoid cascading through IntoGEMObject (which had AlwaysRefCounted as
a supertrait), remove AlwaysRefCounted from IntoGEMObject's supertraits
and instead add it as an explicit bound on lookup_handle(), which is the
only BaseObject method that returns an ARef.
Since Object::new() and shmem::Object::new() return ARef<Self>, move
them to Normal-only impl blocks. Similarly, simplify ObjectConfig and
shmem's parent_resv_obj field to the Normal context.
Remove the DeviceContext generic from DriverObject::new() and
Driver::Object, since GEM objects can only be constructed in the Normal
context. Simplify DriverAllocImpl accordingly.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-8-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Change the default DeviceContext from Registered to Normal for
drm::Device, gem::Object, gem::shmem::Object and
gem::shmem::ObjectConfig.
Normal is the general-purpose, reference-counted context suitable for
most uses; Registered represents a device that was registered with
userspace and will become a non-owning context obtained through a
RegistrationGuard.
Update the create_handle/lookup_handle bounds from Object<Registered> to
Object<Normal> to match the new default context of GEM objects, and
update the driver device type aliases (NovaDevice, TyrDrmDevice) to
default to Normal.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-6-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a ParentDevice associated type to the Driver trait, allowing each
DRM driver to declare its parent bus device type (e.g.
auxiliary::Device, platform::Device).
Change UnregisteredDevice::new() to take &T::ParentDevice<Bound>,
ensuring at the type level that the DRM device's parent matches the
declared bus device type.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-5-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a faux::Device type that wraps struct faux_device and implements
AsBusDevice, enabling faux devices to be used as parent devices for
subsystems that require a bus device, such as DRM.
Update Registration to return &faux::Device<Bound> via AsRef.
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-4-dakr@kernel.org
[ Drop redundant 'struct device' invariant; implied by valid
struct faux_device. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Rename the Uninit DeviceContext to Normal to better reflect its purpose
as the general-purpose, reference-counted device context. The Uninit
name was a leftover from when DRM device private data initialization was
planned to split across UnregisteredDevice::new() and
Registration::new(); with the subsequent introduction of
RegistrationData, this distinction is no longer needed.
This also simplifies the DeviceContext documentation, trimming the
multi-stage initialization description that no longer applies.
Subsequent patches will refine the semantics of the Registered context
accordingly.
No functional change.
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-3-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
References to dev, data, and file in the declare_drm_ioctls! macro are
created via unsafe pointer dereferences, producing unbounded lifetimes.
If an ioctl handler explicitly annotates its parameters with 'static,
the compiler accepts this, allowing the handler to stash references that
outlive the ioctl call.
Fix this by adding a higher-ranked function pointer coercion that
enforces the handler accepts universally quantified lifetimes:
let _: for<'a> fn(&'a _, &'a mut _, &'a _) -> _ = $func;
Since the handler must be coercible to a function pointer accepting any
lifetime 'a, it can no longer demand 'static on any parameter.
Cc: stable@vger.kernel.org
Fixes: 9a69570682 ("rust: drm: ioctl: Add DRM ioctl abstraction")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/all/20260620011346.A47D01F000E9@smtp.kernel.org/
Suggested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260628145406.2107056-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Merge v7.2-rc1 into drm-rust-next to start the next cycle.
Devres now requires T: 'static, which conflicts with shmem::Object using
Devres<SGTableMap<T, C>> without that bound. Resolve by adding 'static
as a supertrait to DriverObject and DeviceContext, which does not
restrict any current use cases since DriverObject is always implemented
on owned, refcounted types and DeviceContext is a sealed marker trait
with only unit-type implementors.
If DriverObject (or DeviceContext) ever becomes lifetime-parameterized
(e.g. via a GAT for TTM backed objects), the 'static supertrait can be
relaxed at that point.
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
In order to do this, we need to be careful to ensure that any interface we
expose for scatterlists ensures that any mappings created from one are
destroyed on driver-unbind. To do this, we introduce a Devres resource into
shmem::Object that we use in order to ensure that we release any SGTable
mappings on driver-unbind.
There's some other slightly unfortunate caveats of this:
* Drivers don't have explicit control at the moment over when unmapping
happens (which is exactly the same as the C side atm, so it might not be
a problem).
* We can't just return `SGTableMap` to the user through an Arc to attempt
to fix the last caveat - because that implies the gem object would need
to hold a reference count to the scatterlist mapping, which just leaves
us with the same problem.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260612194436.585385-5-lyude@redhat.com
If a DriverGpuVm implementation is lifetime-parameterized, its
SmContext<'ctx> type may depend on lifetimes carried by that driver
implementation. In this case, SmContext<'ctx> is only valid if the
driver implementation outlives 'ctx.
Add a Self: 'ctx bound to DriverGpuVm::SmContext<'ctx> to express that
requirement. Then propagate the corresponding T: 'ctx bound to the GPUVM
state machine helper types that store T::SmContext<'ctx>.
This allows drivers to provide lifetime-parameterized implementations of
DriverGpuVm.
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260610-gpuvm_smcontext_lifetime_bound_v1-v1-1-531e7d2ee7b4@collabora.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Since the introduction of DeviceContext, there is no longer a single
driver object type to equate with the GPUVM object type.
Instead of threading DeviceContext through GPUVM, remove the strict
identity between DriverGpuVm::Object and drm::Driver::Object and
instead tighten the requirement that the DriverGpuVm::Object be an
allocatable GEM object associated with the same DRM driver.
Also, make GpuVm::new() generic over DeviceContext so it can accept a
drm::Device<T::Driver, Ctx>.
Fixes: 0023a1e8d0 ("rust/drm/gem: Use DeviceContext with GEM objects")
Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://patch.msgid.link/20260610-gpuvm_device_context_v1-v1-1-01a890b17448@collabora.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
I completely forgot when coming up with this type that #[derive(Default)]
only works if all generics mentioned in the type implement Default (and T
usually doesn't). This being said: We don't use `T` for anything besides
using it for a reference type, so whether or not it implements `Default`
shouldn't actually need to matter.
So, fix this by just manually implementing Default instead of deriving it.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patch.msgid.link/20260603195210.693856-2-lyude@redhat.com
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
One of the tricky things about DRM bindings in Rust is the fact that
initialization of a DRM device is a multi-step process. It's quite normal
for a device driver to start making use of its DRM device for tasks like
creating GEM objects before userspace registration happens. This is an
issue in rust though, since prior to userspace registration the device is
only partly initialized. This means there's a plethora of DRM device
operations we can't yet expose without opening up the door to UB if the DRM
device in question isn't yet registered.
Additionally, this isn't something we can reliably check at runtime. And
even if we could, performing an operation which requires the device be
registered when the device isn't actually registered is a programmer bug,
meaning there's no real way to gracefully handle such a mistake at runtime.
And even if that wasn't the case, it would be horrendously annoying and
noisy to have to check if a device is registered constantly throughout a
driver.
In order to solve this, we first take inspiration from
`kernel::device::DeviceContext` and introduce `kernel::drm::DeviceContext`.
This provides us with a ZST type that we can generalize over to represent
contexts where a device is known to have been registered with userspace at
some point in time (`Registered`), along with contexts where we can't make
such a guarantee (`Uninit`).
It's important to note we intentionally do not provide a `DeviceContext`
which represents an unregistered device. This is because there's no
reasonable way to guarantee that a device with long-living references to
itself will not be registered eventually with userspace. Instead, we
provide a new-type for this: `UnregisteredDevice` which can
provide a guarantee that the `Device` has never been registered with
userspace. To ensure this, we modify `Registration` so that creating a new
`Registration` requires passing ownership of an `UnregisteredDevice`.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://patch.msgid.link/20260507220044.3204919-2-lyude@redhat.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Backmerge to pull in commit 838d852da8 ("rust: allow
`clippy::collapsible_match` globally"), in order to get rid of spurious
warnings messing with developer tooling.
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This provides a mechanism to create (or look up) VMBO instances, which
represent the mapping between GPUVM and GEM objects.
The GpuVmBoRegistered<T> type can be considered like ARef<GpuVm<T>>,
except that no way to increment the refcount is provided.
The GpuVmBoAlloc<T> type is more akin to a pre-allocated GpuVmBo<T>, so
it's not really a GpuVmBo<T> yet. Its destructor could call
drm_gpuvm_bo_destroy_not_in_lists(), but as the type is currently
private and never called anywhere, this perf optimization does not need
to happen now.
Pre-allocating and obtaining the gpuvm_bo object is exposed as a single
step. This could theoretically be a problem if one wanted to call
drm_gpuvm_bo_obtain_prealloc() during the fence signalling critical
path, but that's not a possibility because:
1. Adding the BO to the extobj list requires the resv lock, so it cannot
happen during the fence signalling critical path.
2. obtain() requires that the BO is not in the extobj list, so obtain()
must be called before adding the BO to the extobj list.
Thus, drm_gpuvm_bo_obtain_prealloc() cannot be called during the fence
signalling critical path. (For extobjs at least.)
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260409-gpuvm-rust-v6-2-b16e6ada7261@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Add a GPUVM abstraction to be used by Rust GPU drivers.
GPUVM keeps track of a GPU's virtual address (VA) space and manages the
corresponding virtual mappings represented by "GPU VA" objects. It also
keeps track of the gem::Object<T> used to back the mappings through
GpuVmBo<T>.
This abstraction is only usable by drivers that wish to use GPUVM in
immediate mode. This allows us to build the locking scheme into the API
design. It means that the GEM mutex is used for the GEM gpuva list, and
that the resv lock is used for the extobj list. The evicted list is not
yet used in this version.
This abstraction provides a special handle called the UniqueRefGpuVm,
which is a wrapper around ARef<GpuVm> that provides access to the
interval tree. Generally, all changes to the address space requires
mutable access to this unique handle.
Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Co-developed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Co-developed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260409-gpuvm-rust-v6-1-b16e6ada7261@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
If pinned initialization of drm::Device::Data fails, it calls
drm::Device::release via drm_dev_put. This materializes a reference to
&drm::Device, but it's not fully constructed yet, because initializing
`data` failed. It should not be dropped either. Instead, if pinned
initialization fails, make sure drm::Device::release isn't called.
Fixes: 2e9fdbe5ec ("rust: drm: device: drop_in_place() the drm::Device in release()")
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260501-fix-drm-1-v2-1-5c4f681837bc@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Janne Grunau <j@jananu.net>
Tested-by: Deborah Brouwer <deborah.brouwer@collabora.com>
Link: https://patch.msgid.link/20260316211646.650074-6-lyude@redhat.com
[ * DRM_GEM_SHMEM_HELPER is a tristate; when a module driver selects it,
it becomes =m. The Rust kernel crate and its C helpers are always
built into vmlinux and can't reference symbols from a module,
causing link errors.
Thus, add RUST_DRM_GEM_SHMEM_HELPER bool Kconfig that selects
DRM_GEM_SHMEM_HELPER, forcing it built-in when Rust drivers need it;
use cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER) for the shmem module.
* Add cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), expect(unused))
on pub(crate) use impl_aref_for_gem_obj and BaseObjectPrivate, so
that unused warnings are suppressed when shmem is not enabled.
* Enable const_refs_to_static (stabilized in 1.83) to prevent build
errors with older compilers.
* Use &raw const for bindings::drm_gem_shmem_vm_ops and add
#[allow(unused_unsafe, reason = "Safe since Rust 1.82.0")].
* Fix incorrect C Header path and minor spelling and formatting
issues.
* Drop shmem::Object::sg_table() as the current implementation is
unsound.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
