From patchwork Mon Sep 30 23:09:53 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Lyude Paul X-Patchwork-Id: 13817263 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9D79FCEB2CD for ; Mon, 30 Sep 2024 23:38:48 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 25D8F10E498; Mon, 30 Sep 2024 23:38:48 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="CnAN1Cck"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id 622B310E498 for ; Mon, 30 Sep 2024 23:38:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1727739526; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JlrhV03R2ar0qDWbNL3ocjtNNVJ3Ps0MyvSIOpYYekY=; b=CnAN1Cck4bloD3jmRGEF9xu4XhHB3rOyy8fqUogdkTu0Z1IZwnk0bm+Zx62xffHpLihWGE OK314QfaOUssM5Q8Tfvc9Qd7Ktun606fAGQx5WObdy0sNkPYdxImAXP651Ox46Lw1UPv4o 9R/XB3a8wCpTk1lyMOT4S6AL2R2MYjM= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-628-B90LovqUMrGEpOIDcW1CJw-1; Mon, 30 Sep 2024 19:38:43 -0400 X-MC-Unique: B90LovqUMrGEpOIDcW1CJw-1 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (unknown [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 48B401955F09; Mon, 30 Sep 2024 23:38:40 +0000 (UTC) Received: from chopper.redhat.com (unknown [10.22.32.36]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9E0E33003E4D; Mon, 30 Sep 2024 23:38:36 +0000 (UTC) From: Lyude Paul To: dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org Cc: Asahi Lina , Danilo Krummrich , mcanal@igalia.com, airlied@redhat.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , linux-kernel@vger.kernel.org (open list) Subject: [WIP RFC v2 10/35] rust: drm/kms: Add DriverConnector::get_mode callback Date: Mon, 30 Sep 2024 19:09:53 -0400 Message-ID: <20240930233257.1189730-11-lyude@redhat.com> In-Reply-To: <20240930233257.1189730-1-lyude@redhat.com> References: <20240930233257.1189730-1-lyude@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Next up is filling out some of the basic connector hotplugging callbacks - which we'll need for setting up the fbdev helpers for KMS devices. Note that connector hotplugging in DRM follows a BFL scheme: pretty much all probing is protected under the mighty drm_device->mode_config.lock, which of course is a bit counter-intuitive to rust's locking schemes where data is always associated with its lock. Since that lock is embedded in an FFI type and not a rust type, we need to introduce our own wrapper type that acts as a lock acquisition for this. This brings us to introducing a few new types: * ModeConfigGuard - the most basic lock guard, as long as this object is alive we are guaranteed to be holding drm_device->mode_config.lock. This object doesn't do much else on its own currently. * ConnectorGuard - an object which corresponds to a specific typed DRM connector. This can only be acquired with a ModeConfigGuard, and will be used to allow calling methods that are only safe to call with drm_device->mode_config.lock held. Since it implements Deref> as well, it can also be used for any other operations that would normally be available on a DRM connector. And finally, we add the DriverConnector::get_modes() trait method which drivers can use to implement the drm_connector_helper_funcs.get_modes callback. Note that while we make this trait method mandatory, we only do so for the time being since VKMS doesn't do very much with DRM connectors - and as such we have no need yet to implement alternative connector probing schemes outside of get_modes(). Signed-off-by: Lyude Paul --- rust/kernel/drm/kms.rs | 70 ++++++++++++++++++++++++++++++++ rust/kernel/drm/kms/connector.rs | 57 ++++++++++++++++++++++++-- 2 files changed, 124 insertions(+), 3 deletions(-) diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs index d5cad598f016f..d74267c78864f 100644 --- a/rust/kernel/drm/kms.rs +++ b/rust/kernel/drm/kms.rs @@ -18,6 +18,8 @@ types::*, error::to_result, private::Sealed, + sync::{Mutex, MutexGuard}, + container_of }; use core::{ ops::Deref, @@ -233,6 +235,21 @@ impl KmsDriver for T T: Driver, K: Kms {} +impl Device { + /// Retrieve a pointer to the mode_config mutex + #[inline] + pub(crate) fn mode_config_mutex(&self) -> &Mutex<()> { + // SAFETY: This lock is initialized for as long as `Device` is exposed to users + unsafe { Mutex::from_raw(&mut (*self.as_raw()).mode_config.mutex) } + } + + /// Acquire the [`mode_config.mutex`] for this [`Device`]. + #[inline] + pub fn mode_config_lock(&self) -> ModeConfigGuard<'_, T> { + ModeConfigGuard(self.mode_config_mutex().lock(), PhantomData) + } +} + /// A modesetting object in DRM. /// /// This is any type of object where the underlying C object contains a [`struct drm_mode_object`]. @@ -339,3 +356,56 @@ unsafe fn dec_ref(obj: ptr::NonNull) { unsafe { bindings::drm_mode_object_put(obj.as_ref().raw_mode_obj()) } } } + +/// A mode config guard. +/// +/// This is an exclusive primitive that represents when [`drm_device.mode_config.mutex`] is held - as +/// some modesetting operations (particularly ones related to [`connectors`](connector)) are still +/// protected under this single lock. The lock will be dropped once this object is dropped. +/// +/// # Invariants +/// +/// - `self.0` is contained within a [`struct drm_mode_config`], which is contained within a +/// [`struct drm_device`]. +/// - The [`KmsDriver`] implementation of that [`struct drm_device`] is always `T`. +/// - This type proves that [`drm_device.mode_config.mutex`] is acquired. +/// +/// [`struct drm_mode_config`]: (srctree/include/drm/drm_device.h) +/// [`drm_device.mode_config.mutex`]: (srctree/include/drm/drm_device.h) +/// [`struct drm_device`]: (srctree/include/drm/drm_device.h) +pub struct ModeConfigGuard<'a, T: KmsDriver>(MutexGuard<'a, ()>, PhantomData); + +impl<'a, T: KmsDriver> ModeConfigGuard<'a, T> { + /// Construct a new [`ModeConfigGuard`]. + /// + /// # Safety + /// + /// The caller must ensure that [`drm_device.mode_config.mutex`] is acquired. + /// + /// [`drm_device.mode_config.mutex`]: (srctree/include/drm/drm_device.h) + pub(crate) unsafe fn new(drm: &'a Device) -> Self { + // SAFETY: Our safety contract fulfills the requirements of `MutexGuard::new()` + Self(unsafe { MutexGuard::new(drm.mode_config_mutex(), ()) }, PhantomData) + } + + /// Return the [`Device`] that this [`ModeConfigGuard`] belongs to. + pub fn drm_dev(&self) -> &'a Device { + // SAFETY: + // - `self` is embedded within a `drm_mode_config` via our type invariants + // - `self.0.lock` has an equivalent data type to `mutex` via its type invariants. + let mode_config = unsafe { container_of!(self.0.lock, bindings::drm_mode_config, mutex) }; + + // SAFETY: And that `drm_mode_config` lives in a `drm_device` via type invariants. + unsafe { Device::borrow(container_of!(mode_config, bindings::drm_device, mode_config)) } + } + + /// Assert that the given device is the owner of this mode config guard. + /// + /// # Panics + /// + /// Panics if `dev` is different from the owning device for this mode config guard. + #[inline] + pub(crate) fn assert_owner(&self, dev: &Device) { + assert!(ptr::eq(self.drm_dev(), dev)); + } +} diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs index 54457b327c365..57ab29473c344 100644 --- a/rust/kernel/drm/kms/connector.rs +++ b/rust/kernel/drm/kms/connector.rs @@ -19,7 +19,7 @@ use core::{ marker::*, ptr::null_mut, - mem, + mem::{self, ManuallyDrop}, ptr::{self, NonNull, addr_of_mut}, ffi::*, ops::*, @@ -28,6 +28,7 @@ use super::{ ModeObject, RcModeObject, + ModeConfigGuard, encoder::*, KmsDriver, }; @@ -93,7 +94,7 @@ pub trait DriverConnector: Send + Sync + Sized { destroy: Some(connector_destroy_callback::), force: None, detect: None, - fill_modes: None, + fill_modes: Some(bindings::drm_helper_probe_single_connector_modes), debugfs_init: None, oob_hotplug_event: None, atomic_duplicate_state: Some(atomic_duplicate_state_callback::), @@ -101,7 +102,7 @@ pub trait DriverConnector: Send + Sync + Sized { helper_funcs: bindings::drm_connector_helper_funcs { mode_valid: None, atomic_check: None, - get_modes: None, + get_modes: Some(get_modes_callback::), detect_ctx: None, enable_hpd: None, disable_hpd: None, @@ -132,6 +133,12 @@ pub trait DriverConnector: Send + Sync + Sized { /// /// Drivers may use this to instantiate their [`DriverConnector`] object. fn new(device: &Device, args: Self::Args) -> impl PinInit; + + /// Retrieve a list of available display modes for this [`Connector`]. + fn get_modes<'a>( + connector: ConnectorGuard<'a, Self>, + guard: &ModeConfigGuard<'a, Self::Driver> + ) -> i32; } /// The generated C vtable for a [`DriverConnector`]. @@ -229,6 +236,19 @@ pub fn new( }) } + /// Acquire a [`ConnectorGuard`] for this connector from a [`ModeConfigGuard`]. + /// + /// This verifies using the provided reference that the given guard is actually for the same + /// device as this connector's parent. + /// + /// # Panics + /// + /// Panics if `guard` is not a [`ModeConfigGuard`] for this connector's parent [`Device`]. + pub fn guard<'a>(&'a self, guard: &ModeConfigGuard<'a, T::Driver>) -> ConnectorGuard<'a, T> { + guard.assert_owner(self.drm_dev()); + ConnectorGuard(self) + } + /// Attach an encoder to this [`Connector`]. /// /// TODO: Move this to an `UnregisteredConnector` interface somehow… @@ -327,6 +347,37 @@ unsafe fn from_raw<'a>(ptr: *mut bindings::drm_connector) -> &'a Self { drop(unsafe { Box::from_raw(connector as *mut Connector) }); } +unsafe extern "C" fn get_modes_callback( + connector: *mut bindings::drm_connector, +) -> c_int { + // SAFETY: This is safe via `DriverConnector`s type invariants. + let connector = unsafe { Connector::::from_raw(connector) }; + + // SAFETY: This FFI callback is only called while `mode_config.lock` is held + let guard = ManuallyDrop::new(unsafe { ModeConfigGuard::new(connector.drm_dev()) }); + + T::get_modes(connector.guard(&guard), &guard) +} + +/// A privileged [`Connector`] obtained while holding a [`ModeConfigGuard`]. +/// +/// This provides access to various methods for [`Connector`] that must happen under lock, such as +/// setting resolution preferences and adding display modes. +/// +/// # Invariants +/// +/// Shares the invariants of [`ModeConfigGuard`]. +#[derive(Copy, Clone)] +pub struct ConnectorGuard<'a, T: DriverConnector>(&'a Connector); + +impl Deref for ConnectorGuard<'_, T> { + type Target = Connector; + + fn deref(&self) -> &Self::Target { + self.0 + } +} + // SAFETY: DRM expects this struct to be zero-initialized unsafe impl Zeroable for bindings::drm_connector_state {}