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Message-ID: <0785452f-7714-4384-838b-879e0b224c3c@proton.me>
Date: Wed, 27 Mar 2024 20:50:41 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Lyude Paul <lyude@...hat.com>, dri-devel@...ts.freedesktop.org
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Andreas Hindborg <a.hindborg@...sung.com>, Alice Ryhl <aliceryhl@...gle.com>, Asahi Lina <lina@...hilina.net>, Martin Rodriguez Reboredo <yakoyoku@...il.com>, FUJITA Tomonori <fujita.tomonori@...il.com>, Danilo Krummrich <dakr@...hat.com>, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 1/4] WIP: rust: Add basic KMS bindings
Hi,
I just took a quick look and commented on the things that stuck
out to me. Some general things:
- several `unsafe` blocks have missing SAFETY comments,
- missing documentation and examples.
On 22.03.24 23:03, Lyude Paul wrote:
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
> rust/bindings/bindings_helper.h | 4 +
> rust/helpers.c | 17 ++
> rust/kernel/drm/device.rs | 2 +
> rust/kernel/drm/drv.rs | 115 +++++++--
> rust/kernel/drm/kms.rs | 146 +++++++++++
> rust/kernel/drm/kms/connector.rs | 404 +++++++++++++++++++++++++++++++
> rust/kernel/drm/kms/crtc.rs | 300 +++++++++++++++++++++++
> rust/kernel/drm/kms/encoder.rs | 175 +++++++++++++
> rust/kernel/drm/kms/plane.rs | 300 +++++++++++++++++++++++
> rust/kernel/drm/mod.rs | 1 +
> 10 files changed, 1448 insertions(+), 16 deletions(-)
Please try to break this up into smaller patches. It makes review
a lot easier!
[...]
> diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
> new file mode 100644
> index 0000000000000..b55d14415367a
> --- /dev/null
> +++ b/rust/kernel/drm/kms.rs
> @@ -0,0 +1,146 @@
> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> +
> +//! KMS driver abstractions for rust.
> +
> +pub mod connector;
> +pub mod crtc;
> +pub mod encoder;
> +pub mod plane;
> +
> +use crate::{
> + drm::{drv, device::Device},
> + prelude::*,
> + types::ARef,
> + private::Sealed
> +};
> +use core::{
> + ops::Deref,
> + ptr,
> +};
> +use bindings;
> +
> +#[derive(Copy, Clone)]
> +pub struct ModeConfigInfo {
> + /// The minimum (w, h) resolution this driver can support
> + pub min_resolution: (i32, i32),
> + /// The maximum (w, h) resolution this driver can support
> + pub max_resolution: (i32, i32),
> + /// The maximum (w, h) cursor size this driver can support
> + pub max_cursor: (u32, u32),
> + /// The preferred depth for dumb ioctls
> + pub preferred_depth: u32,
> +}
> +
> +// TODO: I am not totally sure about this. Ideally, I'd like a nice way of hiding KMS-specific
> +// functions for DRM drivers which don't implement KMS - so that we don't have to have a bunch of
> +// random modesetting functions all over the DRM device trait. But, unfortunately I don't know of
> +// any nice way of doing that yet :(
I don't follow, can't you put the KMS specific functions into the
KmsDriver trait?
> +
> +/// An atomic KMS driver implementation
> +pub trait KmsDriver: drv::Driver { }
> +
> +impl<T: KmsDriver> Device<T> {
> + pub fn mode_config_reset(&self) {
> + // SAFETY: The previous build assertion ensures this can only be called for devices with KMS
> + // support, which means mode_config is initialized
> + unsafe { bindings::drm_mode_config_reset(self.drm.get()) }
> + }
> +}
> +
> +/// Main trait for a modesetting object in DRM
> +pub trait ModeObject: Sealed + Send + Sync {
> + /// The parent driver for this ModeObject
> + type Driver: KmsDriver;
> +
> + /// Return the `drv::Device` for this `ModeObject`
> + fn drm_dev(&self) -> &Device<Self::Driver>;
> +}
[...]
> diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
> new file mode 100644
> index 0000000000000..88dfa946d306b
> --- /dev/null
> +++ b/rust/kernel/drm/kms/connector.rs
> @@ -0,0 +1,404 @@
> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> +
> +//! Rust bindings for DRM connectors
> +
> +use crate::{
> + bindings,
> + sync::ArcBorrow,
> + drm::{
> + drv::{Driver, FEAT_MODESET},
> + device::Device,
> + },
> + types::{AlwaysRefCounted, Opaque, ARef},
> + prelude::*,
> + init::Zeroable,
> + error::{to_result, from_result},
> + build_error,
> +};
> +use core::{
> + marker::PhantomPinned,
> + ptr::null_mut,
> + mem,
> + ptr::{self, NonNull},
> + ffi::*,
> + ops::Deref,
> +};
> +use super::{
> + ModeObject,
> + ModeConfigGuard,
> + encoder::{Encoder, DriverEncoder},
> + KmsDriver,
> +};
> +use macros::pin_data;
> +
> +// XXX: This is :\, figure out a better way at some point?
> +pub use bindings::{
> + DRM_MODE_CONNECTOR_Unknown,
> + DRM_MODE_CONNECTOR_VGA,
> + DRM_MODE_CONNECTOR_DVII,
> + DRM_MODE_CONNECTOR_DVID,
> + DRM_MODE_CONNECTOR_DVIA,
> + DRM_MODE_CONNECTOR_Composite,
> + DRM_MODE_CONNECTOR_SVIDEO,
> + DRM_MODE_CONNECTOR_LVDS,
> + DRM_MODE_CONNECTOR_Component,
> + DRM_MODE_CONNECTOR_9PinDIN,
> + DRM_MODE_CONNECTOR_DisplayPort,
> + DRM_MODE_CONNECTOR_HDMIA,
> + DRM_MODE_CONNECTOR_HDMIB,
> + DRM_MODE_CONNECTOR_TV,
> + DRM_MODE_CONNECTOR_eDP,
> + DRM_MODE_CONNECTOR_VIRTUAL,
> + DRM_MODE_CONNECTOR_DSI,
> + DRM_MODE_CONNECTOR_DPI,
> + DRM_MODE_CONNECTOR_WRITEBACK,
> + DRM_MODE_CONNECTOR_SPI,
> + DRM_MODE_CONNECTOR_USB,
> +};
> +
> +/// A DRM connector implementation
> +pub trait DriverConnector: Send + Sync + Sized {
> + /// The return type of the new() function. Should be `impl PinInit<Self, Error>`.
> + /// TODO: Remove this when return_position_impl_trait_in_trait is stable.
> + type Initializer: PinInit<Self, Error>;
This has been stabilized in 1.75.0, so now you should be able to write
fn new(dev: &Device<Self::Driver>, args: Self::Args) -> impl PinInit<Self, Error>;
> +
> + /// The data type to use for passing incoming arguments for new `Connector<T>` instances
> + /// Drivers which don't care about this can just use `()`
> + type Args;
> +
> + /// The parent driver for this DRM connector implementation
> + type Driver: KmsDriver;
> +
> + /// The atomic state implementation for this DRM connector implementation
> + type State: DriverConnectorState;
> +
> + /// Create a new instance of the private driver data struct for this connector in-place
> + fn new(dev: &Device<Self::Driver>, args: Self::Args) -> Self::Initializer;
> +
> + /// Retrieve a list of available display modes for this connector
> + fn get_modes<'a>(
> + connector: ConnectorGuard<'a, Self>,
> + guard: &ModeConfigGuard<'a, Self::Driver>
> + ) -> i32;
> +}
[...]
> diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
> new file mode 100644
> index 0000000000000..3d072028a4884
> --- /dev/null
> +++ b/rust/kernel/drm/kms/crtc.rs
> @@ -0,0 +1,300 @@
> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> +
> +//! KMS driver abstractions for rust.
> +
> +use super::{
> + plane::*,
> + ModeObject,
> + StaticModeObject,
> + KmsDriver
> +};
> +use crate::{
> + bindings,
> + drm::{drv::Driver, device::Device},
> + device,
> + prelude::*,
> + types::Opaque,
> + init::Zeroable,
> + sync::Arc,
> + error::to_result,
> +};
> +use core::{
> + cell::UnsafeCell,
> + marker::PhantomPinned,
> + ptr::{null, null_mut},
> + ops::Deref,
> +};
> +use macros::vtable;
> +
> +/// A typed KMS CRTC with a specific driver.
> +#[repr(C)]
> +#[pin_data]
> +pub struct Crtc<T: DriverCrtc> {
> + // The FFI drm_crtc object
> + pub(super) crtc: Opaque<bindings::drm_crtc>,
> + /// The driver's private inner data
> + #[pin]
> + inner: T,
> + #[pin]
> + _p: PhantomPinned,
Instead of adding this field, you can mark the `crtc` field above as
`#[pin]`. This is because of 0b4e3b6f6b79 ("rust: types: make `Opaque`
be `!Unpin`").
--
Cheers,
Benno
> +}
> +
> +/// KMS CRTC object functions, which must be implemented by drivers.
> +pub trait DriverCrtc: Send + Sync + Sized {
> + /// The return type of the new() function. Should be `impl PinInit<Self, Error>`.
> + /// TODO: Remove this when return_position_impl_trait_in_trait is stable.
> + type Initializer: PinInit<Self, Error>;
> +
> + /// The data type to use for passing incoming arguments for new `Crtc<T>` instances
> + /// Drivers which don't care about this can just use `()`
> + type Args;
> +
> + /// The parent driver implementation
> + type Driver: KmsDriver;
> +
> + /// The type for this driver's drm_crtc_state implementation
> + type State: DriverCrtcState;
> +
> + /// Create a new CRTC for this driver
> + fn new(device: &Device<Self::Driver>, args: Self::Args) -> Self::Initializer;
> +}
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