linux-kernel - Re: [PATCH 2/4] WIP: drm: Introduce rvkms

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Date: Wed, 27 Mar 2024 21:06:42 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Lyude Paul <lyude@...hat.com>, dri-devel@...ts.freedesktop.org
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 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>, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 2/4] WIP: drm: Introduce rvkms

On 22.03.24 23:03, Lyude Paul wrote:
> diff --git a/drivers/gpu/drm/rvkms/connector.rs b/drivers/gpu/drm/rvkms/connector.rs
> new file mode 100644
> index 0000000000000..40f84d38437ee
> --- /dev/null
> +++ b/drivers/gpu/drm/rvkms/connector.rs
> @@ -0,0 +1,55 @@
> +// TODO: License and stuff
> +// Contain's rvkms's drm_connector implementation
> +
> +use super::{RvkmsDriver, RvkmsDevice, MAX_RES, DEFAULT_RES};
> +use kernel::{
> +    prelude::*,
> +    drm::{
> +        device::Device,
> +        kms::{
> +            connector::{self, ConnectorGuard},
> +            ModeConfigGuard
> +        }
> +    },
> +    prelude::*
> +};
> +use core::marker::PhantomPinned;
> +
> +#[pin_data]
> +pub(crate) struct DriverConnector {
> +    #[pin]
> +    _p: PhantomPinned
> +}

This struct does not need to be annotated with `#[pin_data]`, this
should just work:

pub(crate) struct DriverConnector;

> +
> +pub(crate) type Connector = connector::Connector<DriverConnector>;
> +
> +impl connector::DriverConnector for DriverConnector {
> +    type Initializer = impl PinInit<Self, Error>;
> +
> +    type State = ConnectorState;
> +
> +    type Driver = RvkmsDriver;
> +
> +    type Args = ();
> +
> +    fn new(dev: &Device<Self::Driver>, args: Self::Args) -> Self::Initializer {

And then here just return `Self`.

This works, since there is a blanket impl `PinInit<T, E> for T`.

Looking at how you use this API, I am not sure if you actually need
pin-init for the type that implements `DriverConnector`.
Do you need to store eg `Mutex<T>` or something else that needs
pin-init in here in a more complex driver?

-- 
Cheers,
Benno

> +        try_pin_init!(Self { _p: PhantomPinned })
> +    }
> +
> +    fn get_modes(
> +        connector: ConnectorGuard<'_, Self>,
> +        _guard: &ModeConfigGuard<'_, Self::Driver>
> +    ) -> i32 {
> +        let count = connector.add_modes_noedid(MAX_RES);
> +
> +        connector.set_preferred_mode(DEFAULT_RES);
> +        count
> +    }
> +}
> +
> +#[derive(Clone, Default)]
> +pub(crate) struct ConnectorState;
> +
> +impl connector::DriverConnectorState for ConnectorState {
> +    type Connector = DriverConnector;
> +}