{"id":2225770,"url":"http://patchwork.ozlabs.org/api/patches/2225770/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/patch/20260421-io_projection-v2-5-4c251c692ef4@garyguo.net/","project":{"id":28,"url":"http://patchwork.ozlabs.org/api/projects/28/?format=json","name":"Linux PCI development","link_name":"linux-pci","list_id":"linux-pci.vger.kernel.org","list_email":"linux-pci@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260421-io_projection-v2-5-4c251c692ef4@garyguo.net>","list_archive_url":null,"date":"2026-04-21T14:56:16","name":"[v2,05/11] rust: io: restrict untyped IO access and `register!` to `Region`","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"15fbcbf39bb258a6cea9e99f966340c37738de4f","submitter":{"id":76823,"url":"http://patchwork.ozlabs.org/api/people/76823/?format=json","name":"Gary Guo","email":"gary@garyguo.net"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-pci/patch/20260421-io_projection-v2-5-4c251c692ef4@garyguo.net/mbox/","series":[{"id":500833,"url":"http://patchwork.ozlabs.org/api/series/500833/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/list/?series=500833","date":"2026-04-21T14:56:19","name":"rust: I/O type generalization and projection","version":2,"mbox":"http://patchwork.ozlabs.org/series/500833/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2225770/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2225770/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=garyguo.net header.i=@garyguo.net header.a=rsa-sha256\n header.s=selector1 header.b=cm+4JCk3;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c15:e001:75::12fc:5321; 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Wysocki\" , Danilo Krummrich ,\n Miguel Ojeda , Boqun Feng ,\n Gary Guo ,\n =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= ,\n Benno Lossin , Andreas Hindborg ,\n Alice Ryhl , Trevor Gross ,\n Daniel Almeida ,\n Bjorn Helgaas ,\n =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= ,\n Abdiel Janulgue ,\n Robin Murphy ,\n Alexandre Courbot , David Airlie ,\n Simona Vetter ","Cc":"driver-core@lists.linux.dev, rust-for-linux@vger.kernel.org,\n linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,\n nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org","X-Mailer":"b4 0.15.1","X-Developer-Signature":"v=1; a=ed25519-sha256; t=1776783386; l=13259;\n i=gary@garyguo.net; s=20221204; h=from:subject:message-id;\n bh=5GVZfqmlRD7YS7IuSASRsDrAHqXip3Elc7FIgJl4J90=;\n b=c1qQ5DpiFXu6Q0zRPZm7320fqpB78rfHQksb0sudcivMAAKQYhzpxwNBIUibr1/TiYsVppY+p\n 7AbPH/XqylgBDkvynB8TgT9tMoNc/xeftqQZz0KLpoay1KVl9dinsf4","X-Developer-Key":"i=gary@garyguo.net; a=ed25519;\n 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8a6122e1-0478-49c1-b797-08de9fb62b1e","X-MS-Exchange-CrossTenant-AuthSource":"LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM","X-MS-Exchange-CrossTenant-AuthAs":"Internal","X-MS-Exchange-CrossTenant-OriginalArrivalTime":"21 Apr 2026 14:56:29.0683\n (UTC)","X-MS-Exchange-CrossTenant-FromEntityHeader":"Hosted","X-MS-Exchange-CrossTenant-Id":"bbc898ad-b10f-4e10-8552-d9377b823d45","X-MS-Exchange-CrossTenant-MailboxType":"HOSTED","X-MS-Exchange-CrossTenant-UserPrincipalName":"\n 6vlJU61SMvVn1TYtMLIxUaMkpVCJ4xodcqxXU3/UsitaErlu79WNV+uwfUMdnb8hZTwGpTeq5urd7eoD2N4Xwg==","X-MS-Exchange-Transport-CrossTenantHeadersStamped":"CWLP265MB5674"},"content":"Currently the `Io` trait exposes a bunch of untyped IO accesses, but if the\n`Io` region itself is typed, then it might be weird to have\n\n let io: Mmio = /* ... */;\n io.read8(1);\n\nwhile not unsound, it is surely strange. Thus, restrict the untyped methods\nand also the register macro to `Region` type only.\n\nThe way it is implemented is by adding a generic type to `IoLoc`. This also\npaves the way to add typed register blocks in the future; for example, we\ncould use this mechanism to block driver A's `register!()` generated macro\nfrom being used on driver B's MMIO. The same mechanism could be used for\nrelative IO registers. These are future opoortunities, and for this patch I\njust restricted everything to require `IoLoc, _>`.\n\nSuggested-by: Alexandre Courbot \nLink: https://lore.kernel.org/rust-for-linux/DHLB3RO3OSF5.2R7F27U99BKLN@nvidia.com/\nSigned-off-by: Gary Guo \n---\n rust/kernel/io.rs | 47 +++++++++++++++++++++++++++++++---------------\n rust/kernel/io/register.rs | 21 ++++++++++++---------\n 2 files changed, 44 insertions(+), 24 deletions(-)","diff":"diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs\nindex c6d30c5b4e10..a13be8c5fd2d 100644\n--- a/rust/kernel/io.rs\n+++ b/rust/kernel/io.rs\n@@ -238,15 +238,16 @@ pub trait IoCapable {\n /// (for primitive types like [`u32`]) and typed ones (like those generated by the [`register!`]\n /// macro).\n ///\n-/// An `IoLoc` carries three pieces of information:\n+/// An `IoLoc` carries the following pieces of information:\n ///\n+/// - The valid `Base` to operate on. For most registers, this should be [`Region`].\n /// - The offset to access (returned by [`IoLoc::offset`]),\n /// - The width of the access (determined by [`IoLoc::IoType`]),\n /// - The type `T` in which the raw data is returned or provided.\n ///\n /// `T` and `IoLoc::IoType` may differ: for instance, a typed register has `T` = the register type\n /// with its bitfields, and `IoType` = its backing primitive (e.g. `u32`).\n-pub trait IoLoc {\n+pub trait IoLoc {\n /// Size ([`u8`], [`u16`], etc) of the I/O performed on the returned [`offset`](IoLoc::offset).\n type IoType: Into + From;\n \n@@ -254,12 +255,12 @@ pub trait IoLoc {\n fn offset(self) -> usize;\n }\n \n-/// Implements [`IoLoc<$ty>`] for [`usize`], allowing [`usize`] to be used as a parameter of\n-/// [`Io::read`] and [`Io::write`].\n+/// Implements [`IoLoc, $ty>`] for [`usize`], allowing [`usize`] to be used as a\n+/// parameter of [`Io::read`] and [`Io::write`].\n macro_rules! impl_usize_ioloc {\n ($($ty:ty),*) => {\n $(\n- impl IoLoc<$ty> for usize {\n+ impl IoLoc, $ty> for usize {\n type IoType = $ty;\n \n #[inline(always)]\n@@ -328,6 +329,7 @@ fn io_addr(&self, offset: usize) -> Result<*mut U> {\n #[inline(always)]\n fn try_read8(&self, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_read(offset)\n@@ -337,6 +339,7 @@ fn try_read8(&self, offset: usize) -> Result\n #[inline(always)]\n fn try_read16(&self, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_read(offset)\n@@ -346,6 +349,7 @@ fn try_read16(&self, offset: usize) -> Result\n #[inline(always)]\n fn try_read32(&self, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_read(offset)\n@@ -355,6 +359,7 @@ fn try_read32(&self, offset: usize) -> Result\n #[inline(always)]\n fn try_read64(&self, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_read(offset)\n@@ -364,6 +369,7 @@ fn try_read64(&self, offset: usize) -> Result\n #[inline(always)]\n fn try_write8(&self, value: u8, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_write(offset, value)\n@@ -373,6 +379,7 @@ fn try_write8(&self, value: u8, offset: usize) -> Result\n #[inline(always)]\n fn try_write16(&self, value: u16, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_write(offset, value)\n@@ -382,6 +389,7 @@ fn try_write16(&self, value: u16, offset: usize) -> Result\n #[inline(always)]\n fn try_write32(&self, value: u32, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_write(offset, value)\n@@ -391,6 +399,7 @@ fn try_write32(&self, value: u32, offset: usize) -> Result\n #[inline(always)]\n fn try_write64(&self, value: u64, offset: usize) -> Result\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.try_write(offset, value)\n@@ -400,6 +409,7 @@ fn try_write64(&self, value: u64, offset: usize) -> Result\n #[inline(always)]\n fn read8(&self, offset: usize) -> u8\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.read(offset)\n@@ -409,6 +419,7 @@ fn read8(&self, offset: usize) -> u8\n #[inline(always)]\n fn read16(&self, offset: usize) -> u16\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.read(offset)\n@@ -418,6 +429,7 @@ fn read16(&self, offset: usize) -> u16\n #[inline(always)]\n fn read32(&self, offset: usize) -> u32\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.read(offset)\n@@ -427,6 +439,7 @@ fn read32(&self, offset: usize) -> u32\n #[inline(always)]\n fn read64(&self, offset: usize) -> u64\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.read(offset)\n@@ -436,6 +449,7 @@ fn read64(&self, offset: usize) -> u64\n #[inline(always)]\n fn write8(&self, value: u8, offset: usize)\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.write(offset, value)\n@@ -445,6 +459,7 @@ fn write8(&self, value: u8, offset: usize)\n #[inline(always)]\n fn write16(&self, value: u16, offset: usize)\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.write(offset, value)\n@@ -454,6 +469,7 @@ fn write16(&self, value: u16, offset: usize)\n #[inline(always)]\n fn write32(&self, value: u32, offset: usize)\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.write(offset, value)\n@@ -463,6 +479,7 @@ fn write32(&self, value: u32, offset: usize)\n #[inline(always)]\n fn write64(&self, value: u64, offset: usize)\n where\n+ usize: IoLoc,\n Self: IoCapable,\n {\n self.write(offset, value)\n@@ -494,7 +511,7 @@ fn write64(&self, value: u64, offset: usize)\n #[inline(always)]\n fn try_read(&self, location: L) -> Result\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n {\n let address = self.io_addr::(location.offset())?;\n@@ -529,7 +546,7 @@ fn try_read(&self, location: L) -> Result\n #[inline(always)]\n fn try_write(&self, location: L, value: T) -> Result\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n {\n let address = self.io_addr::(location.offset())?;\n@@ -576,8 +593,8 @@ fn try_write(&self, location: L, value: T) -> Result\n #[inline(always)]\n fn try_write_reg(&self, value: V) -> Result\n where\n- L: IoLoc,\n- V: LocatedRegister,\n+ L: IoLoc,\n+ V: LocatedRegister,\n Self: IoCapable,\n {\n let (location, value) = value.into_io_op();\n@@ -610,7 +627,7 @@ fn try_write_reg(&self, value: V) -> Result\n #[inline(always)]\n fn try_update(&self, location: L, f: F) -> Result\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n F: FnOnce(T) -> T,\n {\n@@ -650,7 +667,7 @@ fn try_update(&self, location: L, f: F) -> Result\n #[inline(always)]\n fn read(&self, location: L) -> T\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n {\n let address = self.io_addr_assert::(location.offset());\n@@ -683,7 +700,7 @@ fn read(&self, location: L) -> T\n #[inline(always)]\n fn write(&self, location: L, value: T)\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n {\n let address = self.io_addr_assert::(location.offset());\n@@ -727,8 +744,8 @@ fn write(&self, location: L, value: T)\n #[inline(always)]\n fn write_reg(&self, value: V)\n where\n- L: IoLoc,\n- V: LocatedRegister,\n+ L: IoLoc,\n+ V: LocatedRegister,\n Self: IoCapable,\n {\n let (location, value) = value.into_io_op();\n@@ -761,7 +778,7 @@ fn write_reg(&self, value: V)\n #[inline(always)]\n fn update(&self, location: L, f: F)\n where\n- L: IoLoc,\n+ L: IoLoc,\n Self: IoCapable,\n F: FnOnce(T) -> T,\n {\ndiff --git a/rust/kernel/io/register.rs b/rust/kernel/io/register.rs\nindex 1a407fc35edc..5a7d44c51477 100644\n--- a/rust/kernel/io/register.rs\n+++ b/rust/kernel/io/register.rs\n@@ -113,6 +113,8 @@\n \n use kernel::build_assert;\n \n+use super::Region;\n+\n /// Trait implemented by all registers.\n pub trait Register: Sized {\n /// Backing primitive type of the register.\n@@ -129,7 +131,7 @@ pub trait FixedRegister: Register {}\n \n /// Allows `()` to be used as the `location` parameter of [`Io::write`](super::Io::write) when\n /// passing a [`FixedRegister`] value.\n-impl IoLoc for ()\n+impl IoLoc, T> for ()\n where\n T: FixedRegister,\n {\n@@ -143,7 +145,7 @@ fn offset(self) -> usize {\n \n /// A [`FixedRegister`] carries its location in its type. Thus `FixedRegister` values can be used\n /// as an [`IoLoc`].\n-impl IoLoc for T\n+impl IoLoc, T> for T\n where\n T: FixedRegister,\n {\n@@ -168,7 +170,7 @@ pub const fn new() -> Self {\n }\n }\n \n-impl IoLoc for FixedRegisterLoc\n+impl IoLoc, T> for FixedRegisterLoc\n where\n T: FixedRegister,\n {\n@@ -239,7 +241,8 @@ const fn offset(self) -> usize {\n }\n }\n \n-impl IoLoc for RelativeRegisterLoc\n+// FIXME: Make use of `Base` type parameter of `Region` directly.\n+impl IoLoc, T> for RelativeRegisterLoc\n where\n T: RelativeRegister,\n B: RegisterBase + ?Sized,\n@@ -283,7 +286,7 @@ pub fn try_new(idx: usize) -> Option {\n }\n }\n \n-impl IoLoc for RegisterArrayLoc\n+impl IoLoc, T> for RegisterArrayLoc\n where\n T: RegisterArray,\n {\n@@ -370,7 +373,7 @@ pub fn try_at(self, idx: usize) -> Option> {\n }\n }\n \n-impl IoLoc for RelativeRegisterArrayLoc\n+impl IoLoc, T> for RelativeRegisterArrayLoc\n where\n T: RelativeRegisterArray,\n B: RegisterBase + ?Sized,\n@@ -387,18 +390,18 @@ fn offset(self) -> usize {\n /// which to write it.\n ///\n /// Implementors can be used with [`Io::write_reg`](super::Io::write_reg).\n-pub trait LocatedRegister {\n+pub trait LocatedRegister {\n /// Register value to write.\n type Value: Register;\n /// Full location information at which to write the value.\n- type Location: IoLoc;\n+ type Location: IoLoc;\n \n /// Consumes `self` and returns a `(location, value)` tuple describing a valid I/O write\n /// operation.\n fn into_io_op(self) -> (Self::Location, Self::Value);\n }\n \n-impl LocatedRegister for T\n+impl LocatedRegister> for T\n where\n T: FixedRegister,\n {\n","prefixes":["v2","05/11"]}