From nobody Fri Oct 10 02:44:38 2025 Received: from mout-p-201.mailbox.org (mout-p-201.mailbox.org [80.241.56.171]) (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 C776D2206AA; Mon, 16 Jun 2025 15:45:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.171 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750088732; cv=none; b=nx2Aph+O5VOI+QcTYfrAvAzdCf8ZbaUBH1USn33htElhJPMP3Fqh0++EsKL/mnOpfziox5z7PTwVZul6WI49WN0EtoMQfu+1QHEKb4ivp8deIcZofwXL+XVSMj7pPdFkbGHyS7Z6/0tGJahKYrHY+PvlgJ1Et3mI/Tpr39VqQLk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750088732; c=relaxed/simple; bh=wCc2MJxokZdRhbLuh4AmtlILrl48Ts3XtGp1UmsQOBg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tpFrYytcpU6iFL5ZrQdxbZ3r65Cad3vG1LpfiIe8rVnPZVEj9AmuYfjIlK8i6UCG358Wqm16UUscrL0n6BEkuZErGF6QSgZa7LRD6Aw96n9zzlZAkf50FWb2R1jG8ORpw0WyH+kMXwaY15ChXz3sjI2iuK5Pg+E8cAOnD2KHIww= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=buenzli.dev; spf=pass smtp.mailfrom=buenzli.dev; arc=none smtp.client-ip=80.241.56.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=buenzli.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=buenzli.dev Received: from smtp102.mailbox.org (smtp102.mailbox.org [IPv6:2001:67c:2050:b231:465::102]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4bLZ8R0rZHz9sTh; Mon, 16 Jun 2025 17:45:27 +0200 (CEST) From: Remo Senekowitsch To: Rob Herring , Saravana Kannan , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Mark Brown , Dirk Behme , Remo Senekowitsch Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH v1 2/3] rust: device: Add property_get_reference_args Date: Mon, 16 Jun 2025 17:45:10 +0200 Message-ID: <20250616154511.1862909-3-remo@buenzli.dev> In-Reply-To: <20250616154511.1862909-1-remo@buenzli.dev> References: <20250616154511.1862909-1-remo@buenzli.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 4bLZ8R0rZHz9sTh Content-Type: text/plain; charset="utf-8" Allow Rust code to read reference args from device properties. The wrapper type `FwNodeReferenceArgs` allows callers to access the buffer of read args safely. Signed-off-by: Remo Senekowitsch --- --- rust/kernel/device/property.rs | 102 +++++++++++++++++++++++++++++++++ 1 file changed, 102 insertions(+) diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs index 04a13d05785a..f56ffbd43a94 100644 --- a/rust/kernel/device/property.rs +++ b/rust/kernel/device/property.rs @@ -246,6 +246,99 @@ pub fn children<'a>(&'a self) -> impl Iterator> + 'a { Some(next) }) } + + /// Finds a reference with arguments. + pub fn property_get_reference_args( + &self, + prop: &CStr, + nargs: NArgs<'_>, + index: u32, + ) -> Result { + let mut out_args =3D FwNodeReferenceArgs::default(); + + let (nargs_prop, nargs) =3D match nargs { + NArgs::Prop(nargs_prop) =3D> (nargs_prop.as_char_ptr(), 0), + NArgs::N(nargs) =3D> (ptr::null(), nargs), + }; + + // SAFETY: + // - `self.0.get()` is valid. + // - `prop.as_char_ptr()` is valid and zero-terminated. + // - `nargs_prop` is valid and zero-terminated if `nargs` + // is zero, otherwise it is allowed to be a null-pointer. + // - The function upholds the type invariants of `out_args`, + // namely: + // - It may fill the field `fwnode` with a valid pointer, + // in which case its refcount is incremented. + // - It may modify the field `nargs`, in which case it + // initializes at least as many elements in `args`. + let ret =3D unsafe { + bindings::fwnode_property_get_reference_args( + self.0.get(), + prop.as_char_ptr(), + nargs_prop, + nargs, + index, + &mut out_args.0, + ) + }; + to_result(ret)?; + + Ok(out_args) + } +} + +/// The return value of [`FwNode::property_get_reference_args`]. +/// +/// This structure represents the Rust abstraction for a C +/// `struct fwnode_reference_args` which was initialized by the C side. +/// +/// # Invariants +/// +/// If the field `fwnode` is valid, it owns an increment of its refcount. +/// +/// The field `args` contains at least as many initialized elements as ind= icated +/// by the field `nargs`. +#[repr(transparent)] +#[derive(Default)] +pub struct FwNodeReferenceArgs(bindings::fwnode_reference_args); + +impl Drop for FwNodeReferenceArgs { + fn drop(&mut self) { + if !self.0.fwnode.is_null() { + // SAFETY: + // - By the type invariants of `FwNodeReferenceArgs`, its field + // `fwnode` owns an increment of its refcount. + // - That increment is relinquished. The underlying object won= 't be + // used anymore because we are dropping it. + let _ =3D unsafe { FwNode::from_raw(self.0.fwnode) }; + } + } +} + +impl FwNodeReferenceArgs { + /// Returns the slice of reference arguments. + pub fn as_slice(&self) -> &[u64] { + // SAFETY: As per the safety invariant of `FwNodeReferenceArgs`, `= nargs` + // is the minimum number of elements in `args` that is valid. + unsafe { core::slice::from_raw_parts(self.0.args.as_ptr(), self.0.= nargs as usize) } + } + + /// Returns the number of reference arguments. + pub fn len(&self) -> usize { + self.0.nargs as usize + } + + /// Returns `true` if there are no reference arguments. + pub fn is_empty(&self) -> bool { + self.0.nargs =3D=3D 0 + } +} + +impl core::fmt::Debug for FwNodeReferenceArgs { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + write!(f, "{:?}", self.as_slice()) + } } =20 // SAFETY: Instances of `FwNode` are always reference-counted. @@ -462,6 +555,15 @@ fn read_from_fwnode_property(fwnode: &FwNode, name: &C= Str) -> Result { i64: fwnode_property_read_u64_array, } =20 +/// The number of arguments of a reference. +pub enum NArgs<'a> { + /// The name of the property of the reference indicating the number of + /// arguments. + Prop(&'a CStr), + /// The known number of arguments. + N(u32), +} + /// A helper for reading device properties. /// /// Use [`Self::required_by`] if a missing property is considered a bug and --=20 2.49.0