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[Tracking/Asahi] Rust DRM abstractions #969

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These are the Rust DRM abstractions (and some related changes to the C side) which I use in the Asahi GPU driver. This branch is based on AsahiLinux:gpu/rust-for-later, which is #964.

The Asahi GPU driver compiles successfully on top of this branch.

sulix and others added 30 commits February 17, 2023 00:50
@sulix @asahilina
rust: kernel: Mark rust_fmt_argument as extern "C"
38717bd 
The rust_fmt_argument function is called from printk() to handle the %pA
format specifier.

Since it's called from C, we should mark it extern "C" to make sure it's
ABI compatible.

Cc: [email protected]
Fixes: 247b365 ("rust: add `kernel` crate")
Signed-off-by: David Gow <[email protected]>
Link: Rust-for-Linux#967
Reviewed-by: Björn Roy Baron <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
[Applied `rustfmt`]
Signed-off-by: Miguel Ojeda <[email protected]>
@asahilina
soc: apple: rtkit: Add a private pointer to apple_rtkit_shmem
bcfd851 
This allows downstream consumers to keep track of private data for shmem
mappings. In particular, the Rust abstraction will use this to safely
drop data associated with a mapping when it is unmapped.

Signed-off-by: Asahi Lina <[email protected]>
Reviewed-by: Sven Peter <[email protected]>
Reviewed-by: Eric Curtin <[email protected]>
Signed-off-by: Hector Martin <[email protected]>
@asahilina
soc: apple: rtkit: Export non-devm init/free functions
5f9a6ba 
While we normally encourage devm usage by drivers, some consumers (and
in particular the upcoming Rust abstractions) might want to manually
manage memory. Export the raw functions to make this possible.

Signed-off-by: Asahi Lina <[email protected]>
Reviewed-by: Sven Peter <[email protected]>
Reviewed-by: Eric Curtin <[email protected]>
Signed-off-by: Hector Martin <[email protected]>
@asahilina
drm/gem-shmem: Fix locking for drm_gem_shmem_get_pages_sgt()
3c3f227 
Other functions touching shmem->sgt take the pages lock, so do that here
too. drm_gem_shmem_get_pages() & co take the same lock, so move to the
_locked() variants to avoid recursive locking.

Signed-off-by: Asahi Lina <[email protected]>
@ojeda @asahilina
arm64: rust: Enable Rust support for AArch64
a38c023 
This commit provides the build flags for Rust for AArch64. The core Rust
support already in the kernel does the rest.

The Rust samples have been tested with this commit.

[jcunliffe: Arm specific parts taken from Miguel's upstream tree]

Signed-off-by: Miguel Ojeda <[email protected]>
Co-developed-by: Jamie Cunliffe <[email protected]>
Signed-off-by: Jamie Cunliffe <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
Signed-off-by: Vincenzo Palazzo <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
@JamieCunliffe @asahilina
arm64: rust: Enable PAC support for Rust.
135e133 
Enable the PAC ret and BTI options in the Rust build flags to match
the options that are used when building C.

Signed-off-by: Jamie Cunliffe <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
@JamieCunliffe @asahilina
arm64: rust: Disable neon and fp target features.
3ca7478 
Disable the neon and fp target features to avoid fp & simd
registers. The use of fp-armv8 will cause a warning from rustc about
an unknown feature that is specified. The target feature is still
passed through to LLVM, this behaviour is documented as part of the
warning. This will be fixed in a future version of the rustc
toolchain.

Signed-off-by: Jamie Cunliffe <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
@fbq @asahilina
rust: sync: impl {Debug,Display} for {Unique,}Arc
4c9658b 
This allows printing the inner data of `Arc` and its friends if the
inner data implements `Display` or `Debug`. It's useful for logging and
debugging purpose.

Signed-off-by: Boqun Feng <[email protected]>
Reviwed-by: Vincenzo Palazzo <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Björn Roy Baron <[email protected]>
@fbq @asahilina
sample: rust: print: Add sampe code for Arc printing
a0fe4ac 
This both demonstrates the usage of different print format in Rust and
serves as a selftest for the `Display` and `Debug` implementation of
`Arc` and its friends.

Signed-off-by: Boqun Feng <[email protected]>
Reviewed-by: Björn Roy Baron <[email protected]>
Reviewed-by: Finn Behrens <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
@asahilina
rust: time: New module for timekeeping functions
05228e7 
This module is intended to contain functions related to kernel
timekeeping and time. Initially, this just wraps ktime_get() and
ktime_get_boottime() and returns them as core::time::Duration instances.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: macros: Make expect_punct() return the Punct directly
ea1e536 
This makes it mirror the way expect_ident() works, and means we can more
easily push the result back into the token stream.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: concat_idents: Allow :: paths in first argument
5341cab 
This makes things like concat_idents!(bindings::foo, bar) work.
Otherwise, there is no way to concatenate two idents and then use the
result as part of a type path.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: macros: Allow specifying multiple module aliases
b41f846 
Modules can (and usually do) have multiple alias tags, in order to
specify multiple possible device matches for autoloading. Allow this by
changing the alias ModuleInfo field to an Option<Vec<String>>.

Note: For normal device IDs this is autogenerated by modpost (which is
not properly integrated with Rust support yet), so it is useful to be
able to manually add device match aliases for now, and should still be
useful in the future for corner cases that modpost does not handle.

This pulls in the expect_group() helper from the rfl/rust branch
(with credit to authors).

Co-developed-by: Miguel Ojeda <[email protected]>
Co-developed-by: Finn Behrens <[email protected]>
Co-developed-by: Sumera Priyadarsini <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: ioctl: Add ioctl number manipulation functions
8f9792c 
Add simple 1:1 wrappers of the C ioctl number manipulation functions.
Since these are macros we cannot bindgen them directly, and since they
should be usable in const context we cannot use helper wrappers, so
we'll have to reimplement them in Rust. Thankfully, the C headers do
declare defines for the relevant bitfield positions, so we don't need
to duplicate that.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: sync: arc: implement Arc<dyn Any + Send + Sync>::downcast()
4c2677a 
This mirrors the standard library's alloc::sync::Arc::downcast().

Based on the Rust standard library implementation, ver 1.62.0,
licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.62.0/library/alloc/src

For copyright details, please see:

        https://github.com/rust-lang/rust/blob/1.62.0/COPYRIGHT

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: Enable feature new_uninit for the kernel crate
7402be1 
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: sync: arc: Add UniqueArc<MaybeUninit<T>::assume_init()
b5907a1 
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: error: Add Error::to_ptr()
d898a36 
This is the Rust equivalent to ERR_PTR(), for use in C callbacks.
Marked as #[allow(dead_code)] for now, since it does not have any
consumers yet.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: error: Add Error::from_kernel_errno()
8b14bb1 
Add a function to create `Error` values out of a kernel error return,
which safely upholds the invariant that the error code is well-formed
(negative and greater than -MAX_ERRNO). If a malformed code is passed
in, it will be converted to EINVAL.

Imported from rust-for-linux/rust as authored by Miguel and Fox with
refactoring from Wedson.

Co-developed-by: Miguel Ojeda <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: error: Add to_result() helper
86dcd64 
Add a to_result() helper to convert kernel C return values to a Rust
Result, mapping >=0 values to Ok(()) and negative values to Err(...),
with Error::from_kernel_errno() ensuring that the errno is within range.

Imported from rust-for-linux/rust, originally developed by Wedson as part of the
AMBA device driver support.

Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: error: Add a helper to convert a C ERR_PTR to a Result
b376b28 
Some kernel C API functions return a pointer which embeds an optional
`errno`. Callers are supposed to check the returned pointer with
`IS_ERR()` and if this returns `true`, retrieve the `errno` using
`PTR_ERR()`.

Create a Rust helper function to implement the Rust equivalent:
transform a `*mut T` to `Result<*mut T>`.

Lina: Imported from rust-for-linux/linux, with subsequent refactoring
and contributions squashed in and attributed below. Replaced usage of
from_kernel_errno_unchecked() with an open-coded constructor, since this
is the only user anyway.

Co-developed-by: Boqun Feng <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Co-developed-by: Miguel Ojeda <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Gary Guo <[email protected]>
Signed-off-by: Gary Guo <[email protected]>
Signed-off-by: Sven Van Asbroeck <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: error: Add from_kernel_result!() macro
f325dc8 
Add a helper macro to easily return C result codes from a Rust function
that calls functions which return a Result<T>.

Imported from rust-for-linux/rust, originally developed by Wedson as
part of file_operations.rs.

Co-developed-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Co-developed-by: Fox Chen <[email protected]>
Signed-off-by: Fox Chen <[email protected]>
Co-developed-by: Miguel Ojeda <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: Import upstream alloc::vec::set_len_on_drop module
834ba12 
This is a subset of the Rust standard library `alloc` crate,
version 1.66.0, licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.66.0/library/alloc/src

The file is copied as-is, with no modifications whatsoever
(not even adding the SPDX identifiers).

For copyright details, please see:

    https://github.com/rust-lang/rust/blob/1.66.0/COPYRIGHT

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: Import upstream alloc::vec::spec_extend module
25c7313 
This is a subset of the Rust standard library `alloc` crate,
version 1.66.0, licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.66.0/library/alloc/src

The file is copied as-is, with no modifications whatsoever
(not even adding the SPDX identifiers).

For copyright details, please see:

    https://github.com/rust-lang/rust/blob/1.66.0/COPYRIGHT

Signed-off-by: Asahi Lina <[email protected]>
@ojeda @asahilina
rust: alloc: vec: Add some try_* methods we need
bdeae64 
Add some missing fallible methods that we need.

They are all marked as:

    #[stable(feature = "kernel", since = "1.0.0")]

for easy identification.

Lina: Extracted from 487d757 ("rust: alloc: add some `try_*`
methods we need") in rust-for-linux/rust.

Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: xarray: Add an abstraction for XArray
9a99c88 
The XArray is an abstract data type which behaves like a very large
array of pointers. Add a Rust abstraction for this data type.

The initial implementation uses explicit locking on get operations and
returns a guard which blocks mutation, ensuring that the referenced
object remains alive. To avoid excessive serialization, users are
expected to use an inner type that can be efficiently cloned (such as
Arc<T>), and eagerly clone and drop the guard to unblock other users
after a lookup.

Future variants may support using RCU instead to avoid mutex locking.

This abstraction also introduces a reservation mechanism, which can be
used by alloc-capable XArrays to reserve a free slot without immediately
filling it, and then do so at a later time. If the reservation is
dropped without being filled, the slot is freed again for other users,
which eliminates the need for explicit cleanup code.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: Add a Sealed trait
3a1cbaa 
Some traits exposed by the kernel crate may not be intended to be
implemented by downstream modules. Add a Sealed trait to allow avoiding
this using the sealed trait pattern.

Signed-off-by: Asahi Lina <[email protected]>
@wedsonaf @asahilina
rust: device: Add an abstraction for devices
8d62ad9 
Add a RawDevice trait which can be implemented by any type representing
a device class (such as a PlatformDevice), and a Device type which
represents an owned reference to a generic struct device.

Lina: Rewrote commit message, dropped the Amba bits, and squashed in
simple changes to the core RawDevice/Device code from latter commits
in rust-for-linux/rust. Also include the rust_helper_dev_get_drvdata
helper which will be needed by consumers later on.

Co-developed-by: Miguel Ojeda <[email protected]>
Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Wedson Almeida Filho <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: io_pgtable: Add io_pgtable abstraction
6f5b56e 
The io_pgtable subsystem implements page table management for various
IOMMU page table formats. This abstraction allows Rust drivers for
devices with an embedded MMU to use this shared code.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: soc: apple: rtkit: Add Apple RTKit abstraction
07df4ec 
RTKit is Apple's proprietary real-time operating system framework, used
across many subdevices on Apple Silicon platforms including NVMe, system
management, GPU, etc. Add Rust abstractions for this subsystem, so that
it can be used by upcoming Rust drivers.

Note: Although ARM64 support is not yet merged, this can be built on amd64
with CONFIG_COMPILE_TEST=y.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
drm/gem-shmem: Export VM ops functions
a640ef1 
There doesn't seem to be a way for the Rust bindings to get a
compile-time constant reference to drm_gem_shmem_vm_ops, so we need to
duplicate that structure in Rust... this isn't nice...

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: drm: gem: shmem: Add DRM shmem helper abstraction
36a79c2 
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 <[email protected]>
@asahilina
rust: drm: mm: Add DRM MM Range Allocator abstraction
bc228ef 
drm_mm provides a simple range allocator, useful for managing virtual
address ranges. Add a Rust abstraction to expose this module to Rust
drivers.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: dma_fence: Add DMA Fence abstraction
fe6eb9c 
DMA fences are the internal synchronization primitive used for DMA
operations like GPU rendering, video en/decoding, etc. Add an
abstraction to allow Rust drivers to interact with this subsystem.

Note: This uses a raw spinlock living next to the fence, since we do
not interact with it other than for initialization.
TODO: Expose this to the user at some point with a safe abstraction.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: drm: syncobj: Add DRM Sync Object abstraction
3b08232 
DRM Sync Objects are a container for a DMA fence, and can be waited on
signaled, exported, and imported from userspace. Add a Rust abstraction
so Rust DRM drivers can support this functionality.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
drm/sched: Add can_run_job callback
6fbf03a 
Some hardware may require more complex resource utilization accounting
than the simple job count supported by drm_sched internally. Add a
can_run_job callback to allow drivers to implement more logic before
deciding whether to run a GPU job.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: drm: sched: Add GPU scheduler abstraction
689f400 
The GPU scheduler manages scheduling GPU jobs and dependencies between
them. This Rust abstraction allows Rust DRM drivers to use this
functionality.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
drm/gem: Add a flag to control whether objects can be exported
62bdaa1 
Drivers may want to support driver-private objects, which cannot be
shared. This allows them to share a single lock and enables other
optimizations.

Add an `exportable` field to drm_gem_object, which blocks PRIME export
if set to false. It is initialized to true in
drm_gem_private_object_init.

Signed-off-by: Asahi Lina <[email protected]>
@asahilina
rust: drm: gem: Add set_exportable() method
e37ed51 
This allows drivers to control whether a given GEM object is allowed to
be exported via PRIME to other drivers.
@ojeda ojeda force-pushed the rust-next branch 4 times, most recently from ffa6a7f to 1944caa Compare April 12, 2023 16:49
@MageiaLinuxOnSiliconDevices
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I don't mean to sound rude and I'm certainly not an expert, but shouldn't the conflicts be dealt with as well?

@y86-dev
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y86-dev commented Apr 29, 2023 •
edited
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The development of the Linux kernel happens on the LKML (Linux Kernel Mailing List). There a patch based approach is used that are based on a common ancestor (often an -rcX release or rust-next). Any PRs to the rust-next branch are only for tracking who is working on what and quickly iterating on code.

Maintainers will fix conflicts for patches that have been fully reviewed and will put them into their respective next branch.

So having conflicts in GH does not really mean anything.

@ojeda
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ojeda commented Apr 29, 2023

Also, please see https://rust-for-linux.com/contributing and https://rust-for-linux.com/branches.

@ojeda ojeda force-pushed the rust-next branch 3 times, most recently from c9b5ce6 to ce1c54f Compare October 9, 2024 22:37
@ojeda ojeda force-pushed the rust-next branch 3 times, most recently from 9ee7197 to 6ce162a Compare October 15, 2024 21:11
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8 participants
@asahilina @MageiaLinuxOnSiliconDevices @y86-dev @ojeda @sulix @JamieCunliffe @fbq @wedsonaf