| Message ID | 475bc73d8d11290446a4135af76aea123c6d80ee.1744366571.git.viresh.kumar@linaro.org (mailing list archive) |
|---|---|
| State | Under Review |
| Headers | show |
| Series | Rust abstractions for clk, cpumask, cpufreq, OPP | expand |
On Fri, Apr 11, 2025 at 04:25:08PM +0530, Viresh Kumar wrote: > This implements cpu::from_cpu(), which returns a reference to > Device for a CPU. The C struct is created at initialization time for > CPUs and is never freed and so ARef isn't returned from this function. > > The new helper will be used by Rust based cpufreq drivers. > > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> > --- > MAINTAINERS | 1 + > rust/bindings/bindings_helper.h | 1 + > rust/kernel/cpu.rs | 31 +++++++++++++++++++++++++++++++ > rust/kernel/lib.rs | 1 + > 4 files changed, 34 insertions(+) > create mode 100644 rust/kernel/cpu.rs > > diff --git a/MAINTAINERS b/MAINTAINERS > index 12cde55579a0..475abf72869c 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -6155,6 +6155,7 @@ F: include/linux/cpuhotplug.h > F: include/linux/smpboot.h > F: kernel/cpu.c > F: kernel/smpboot.* > +F: rust/kernel/cpu.rs > > CPU IDLE TIME MANAGEMENT FRAMEWORK > M: "Rafael J. Wysocki" <rafael@kernel.org> > diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h > index f53d6e1a21f2..ac92c67d2c38 100644 > --- a/rust/bindings/bindings_helper.h > +++ b/rust/bindings/bindings_helper.h > @@ -11,6 +11,7 @@ > #include <linux/blk_types.h> > #include <linux/blkdev.h> > #include <linux/clk.h> > +#include <linux/cpu.h> > #include <linux/cpumask.h> > #include <linux/cred.h> > #include <linux/device/faux.h> > diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs > new file mode 100644 > index 000000000000..3054165d3818 > --- /dev/null > +++ b/rust/kernel/cpu.rs > @@ -0,0 +1,31 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +//! Generic CPU definitions. > +//! > +//! C header: [`include/linux/cpu.h`](srctree/include/linux/cpu.h) > + > +use crate::{bindings, device::Device, error::Result, prelude::ENODEV}; > + > +/// Creates a new instance of CPU's device. > +/// > +/// # Safety > +/// > +/// Reference counting is not implemented for the CPU device in the C code. When a CPU is > +/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory > +/// is not freed. > +/// > +/// Callers must ensure that the CPU device is not used after it has been unregistered. > +/// This can be achieved, for example, by registering a CPU hotplug notifier and removing > +/// any references to the CPU device within the notifier's callback. > +pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> { > + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to > + // a `struct device` and is never freed by the C code. > + let ptr = unsafe { bindings::get_cpu_device(cpu) }; > + if ptr.is_null() { > + return Err(ENODEV); > + } > + > + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to > + // a `struct device` and is never freed by the C code. If you think that writing the same thing twice would help in SAFETY department, I'd recommend you to write it for a couple more times. > + Ok(unsafe { Device::as_ref(ptr) }) > +} > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs > index f4dcfefe94be..db372f806875 100644 > --- a/rust/kernel/lib.rs > +++ b/rust/kernel/lib.rs > @@ -44,6 +44,7 @@ > pub mod build_assert; > #[cfg(CONFIG_COMMON_CLK)] > pub mod clk; > +pub mod cpu; > pub mod cpumask; > pub mod cred; > pub mod device; > -- > 2.31.1.272.g89b43f80a514
On Fri, Apr 11, 2025 at 12:18:26PM -0400, Yury Norov wrote: > On Fri, Apr 11, 2025 at 04:25:08PM +0530, Viresh Kumar wrote: > > +/// Creates a new instance of CPU's device. > > +/// > > +/// # Safety > > +/// > > +/// Reference counting is not implemented for the CPU device in the C code. When a CPU is > > +/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory > > +/// is not freed. > > +/// > > +/// Callers must ensure that the CPU device is not used after it has been unregistered. > > +/// This can be achieved, for example, by registering a CPU hotplug notifier and removing > > +/// any references to the CPU device within the notifier's callback. > > +pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> { > > + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to > > + // a `struct device` and is never freed by the C code. > > + let ptr = unsafe { bindings::get_cpu_device(cpu) }; You don't need to justify the return value here, you need to justify why cpu is a valid value to call get_cpu_device() with. > > + if ptr.is_null() { > > + return Err(ENODEV); > > + } > > + > > + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to > > + // a `struct device` and is never freed by the C code. Here, the comment is good. > If you think that writing the same thing twice would help in SAFETY > department, I'd recommend you to write it for a couple more times. Fixing the above, should also fix the duplication. :) > > + Ok(unsafe { Device::as_ref(ptr) })
diff --git a/MAINTAINERS b/MAINTAINERS index 12cde55579a0..475abf72869c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6155,6 +6155,7 @@ F: include/linux/cpuhotplug.h F: include/linux/smpboot.h F: kernel/cpu.c F: kernel/smpboot.* +F: rust/kernel/cpu.rs CPU IDLE TIME MANAGEMENT FRAMEWORK M: "Rafael J. Wysocki" <rafael@kernel.org> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index f53d6e1a21f2..ac92c67d2c38 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -11,6 +11,7 @@ #include <linux/blk_types.h> #include <linux/blkdev.h> #include <linux/clk.h> +#include <linux/cpu.h> #include <linux/cpumask.h> #include <linux/cred.h> #include <linux/device/faux.h> diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs new file mode 100644 index 000000000000..3054165d3818 --- /dev/null +++ b/rust/kernel/cpu.rs @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Generic CPU definitions. +//! +//! C header: [`include/linux/cpu.h`](srctree/include/linux/cpu.h) + +use crate::{bindings, device::Device, error::Result, prelude::ENODEV}; + +/// Creates a new instance of CPU's device. +/// +/// # Safety +/// +/// Reference counting is not implemented for the CPU device in the C code. When a CPU is +/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory +/// is not freed. +/// +/// Callers must ensure that the CPU device is not used after it has been unregistered. +/// This can be achieved, for example, by registering a CPU hotplug notifier and removing +/// any references to the CPU device within the notifier's callback. +pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> { + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to + // a `struct device` and is never freed by the C code. + let ptr = unsafe { bindings::get_cpu_device(cpu) }; + if ptr.is_null() { + return Err(ENODEV); + } + + // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to + // a `struct device` and is never freed by the C code. + Ok(unsafe { Device::as_ref(ptr) }) +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index f4dcfefe94be..db372f806875 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -44,6 +44,7 @@ pub mod build_assert; #[cfg(CONFIG_COMMON_CLK)] pub mod clk; +pub mod cpu; pub mod cpumask; pub mod cred; pub mod device;
This implements cpu::from_cpu(), which returns a reference to Device for a CPU. The C struct is created at initialization time for CPUs and is never freed and so ARef isn't returned from this function. The new helper will be used by Rust based cpufreq drivers. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- MAINTAINERS | 1 + rust/bindings/bindings_helper.h | 1 + rust/kernel/cpu.rs | 31 +++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 1 + 4 files changed, 34 insertions(+) create mode 100644 rust/kernel/cpu.rs