From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5CA4D2EBDE0; Tue, 22 Jul 2025 15:01:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753196484; cv=none; b=hV881vHPDqb/avgKcUCMzyKRaA9ngxtG6iwJIGxxpAk7AEQAfc48Bs/QDmy4Ftm7EsyLDqfwPWPUXL/FDna/z6vpfTHTyto+MdBLnOxwmNfsFsJnMj9yGNRx1Xp7WUQxnntTQxbCAmt0lUrAzuNtOEyI6vYv2HMw9DdlY851t10= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753196484; c=relaxed/simple; bh=kbZWRBa133EyVivWNfo1Ul3K7i+pBTVUEjE7NjH9MBc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I+uI6ibcxH8OL5YAzKRYEKfWx2dsr+JirGXoqqomsCJvRlffrGCLaxYLfirD7TG3GVBWF9zKkralgJkLwh0VcoRxF8mmNpCI93uGnng/PsW1VNXhy33M2u+3D1BhpEgNTwsCZF3u65o7lgqSyLbXA6oIzorgZDx5lj9z2UvBYTs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=i8Z4wTCf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="i8Z4wTCf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A4B1C4CEF6; Tue, 22 Jul 2025 15:01:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1753196483; bh=kbZWRBa133EyVivWNfo1Ul3K7i+pBTVUEjE7NjH9MBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i8Z4wTCf0+vYr2bTPcGLUdO4gDQBfhPmmiAfSstCLmqcGos4IavqLT3+le8QZ7wKJ cbSnyAWGasW5aem4f/Cv9CWfB3AnQVwepNevQf3zrNTIoRis+hYDXx2qbrDL35f/fK dEDnQSl1LsBnLbQgBEOZMKJvOsLpZv4x7XiKO2S55DrSxUfMzflwpNiC1vW8e4ttdL spmFP8Lns9tpszA7e4AS1xfQDdUNfFLR1Atq2fOItNJ9zsn1QO0/5eFjSysxlCy4Mv 2uYC5Sbfv15kqdcgKSJZyffcFe2PiS2w4MjcfoCsK095PbZ8vPoR7jjRnMR8DiDe4/ +uC+rIl15wpcw== From: Danilo Krummrich To: gregkh@linuxfoundation.org, rafael@kernel.org, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Danilo Krummrich Subject: [PATCH v2 1/3] device: rust: expand documentation for DeviceContext Date: Tue, 22 Jul 2025 16:59:59 +0200 Message-ID: <20250722150110.23565-2-dakr@kernel.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250722150110.23565-1-dakr@kernel.org> References: <20250722150110.23565-1-dakr@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Expand the documentation around DeviceContext states and types, in order to provide detailed information about their purpose and relationship with each other. Reviewed-by: Greg Kroah-Hartman Signed-off-by: Danilo Krummrich --- rust/kernel/device.rs | 69 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 58 insertions(+), 11 deletions(-) diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index ca82926fd67f..f5d1db568f00 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -311,28 +311,75 @@ unsafe impl Send for Device {} // synchronization in `struct device`. unsafe impl Sync for Device {} -/// Marker trait for the context of a bus specific device. +/// Marker trait for the context or scope of a bus specific device. /// -/// Some functions of a bus specific device should only be called from a certain context, i.e. bus -/// callbacks, such as `probe()`. +/// [`DeviceContext`] is a marker trait for types representing the context of a bus specific +/// [`Device`]. /// -/// This is the marker trait for structures representing the context of a bus specific device. +/// The specific device context types are: [`CoreInternal`], [`Core`], [`Bound`] and [`Normal`]. +/// +/// [`DeviceContext`] types are hierarchical, which means that there is a strict hierarchy that +/// defines which [`DeviceContext`] type can be derived from another. For instance, any +/// [`Device`] can dereference to a [`Device`]. +/// +/// The following enunumeration illustrates the dereference hierarchy of [`DeviceContext`] types. +/// +/// - [`CoreInternal`] => [`Core`] => [`Bound`] => [`Normal`] +/// +/// Bus devices can automatically implement the dereference hierarchy by using +/// [`impl_device_context_deref`]. +/// +/// Note that the guarantee for a [`Device`] reference to have a certain [`DeviceContext`] comes +/// from the specific scope the [`Device`] reference is valid in. +/// +/// [`impl_device_context_deref`]: kernel::impl_device_context_deref pub trait DeviceContext: private::Sealed {} -/// The [`Normal`] context is the context of a bus specific device when it is not an argument of -/// any bus callback. +/// The [`Normal`] context is the default [`DeviceContext`] of any [`Device`]. +/// +/// The normal context does not indicate any specific context. Any `Device` is also a valid +/// [`Device`]. It is the only [`DeviceContext`] for which it is valid to implement +/// [`AlwaysRefCounted`] for. +/// +/// [`AlwaysRefCounted`]: kernel::types::AlwaysRefCounted pub struct Normal; -/// The [`Core`] context is the context of a bus specific device when it is supplied as argument of -/// any of the bus callbacks, such as `probe()`. +/// The [`Core`] context is the context of a bus specific device when it appears as argument of +/// any bus specific callback, such as `probe()`. +/// +/// The core context indicates that the [`Device`] reference's scope is limited to the bus +/// callback it appears in. It is intended to be used for synchronization purposes. Bus device +/// implementations can implement methods for [`Device`], such that they can only be called +/// from bus callbacks. pub struct Core; -/// Semantically the same as [`Core`] but reserved for internal usage of the corresponding bus +/// Semantically the same as [`Core`], but reserved for internal usage of the corresponding bus +/// abstraction. +/// +/// The internal core context is intended to be used in exactly the same way as the [Core] context, +/// with the difference that this [`DeviceContext`] is internal to the corresponding bus /// abstraction. +/// +/// This context mainly exists to share generic [`Device`] infrastructure that should only be called +/// from bus callbacks with bus abstractions, but without making them accessible for drivers. pub struct CoreInternal; -/// The [`Bound`] context is the context of a bus specific device reference when it is guaranteed to -/// be bound for the duration of its lifetime. +/// The [`Bound`] context is the [`DeviceContext`] of a bus specific device when it is guaranteed to +/// be bound to a driver. +/// +/// The bound context indicates that for the entire duration of the lifetime of a [`Device`] +/// reference, the [`Device`] is guaranteed to be bound to a driver. +/// +/// Some APIs, such as [`dma::CoherentAllocation`] or [`Devres`] rely on the [`Device`] to be bound, +/// which can be proven with the [`Bound`] device context. +/// +/// Any abstraction that can guarantee a scope where the corresponding bus device is bound, should +/// provide a [`Device`] reference to its users for this scope. This allows users to benefit +/// from optimizations for accessing device resources, see also [`Devres::access`]. +/// +/// [`Devres`]: kernel::devres::Devres +/// [`Devres::access`]: kernel::devres::Devres::access +/// [`dma::CoherentAllocation`]: kernel::dma::CoherentAllocation pub struct Bound; mod private { -- 2.50.0