Implement ForLt and CovariantForLt for IoMem<'static, SIZE> and ExclusiveIoMem<'static, SIZE> so that DevresLt can shorten the stored 'static lifetime back to the caller's borrow lifetime.
CovariantForLt is sound because both types only hold &'a Device<Bound>, which is covariant over 'a. Since DevresLt::new() handles the lifetime transmutation internally, into_devres() no longer needs an explicit transmute to 'static. Add DevresIoMem<SIZE> and DevresExclusiveIoMem<SIZE> type aliases. Signed-off-by: Danilo Krummrich <[email protected]> --- drivers/pwm/pwm_th1520.rs | 5 ++- rust/kernel/io/mem.rs | 65 +++++++++++++++++++++++++++------------ 2 files changed, 47 insertions(+), 23 deletions(-) diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs index 48808cd80737..7e3a06ed369f 100644 --- a/drivers/pwm/pwm_th1520.rs +++ b/drivers/pwm/pwm_th1520.rs @@ -24,9 +24,8 @@ use kernel::{ clk::Clk, device::{Bound, Core, Device}, - devres, io::{ - mem::IoMem, + mem::DevresIoMem, Io, // }, of, platform, @@ -92,7 +91,7 @@ struct Th1520WfHw { #[pin_data(PinnedDrop)] struct Th1520PwmDriverData { #[pin] - iomem: devres::Devres<IoMem<'static, TH1520_PWM_REG_SIZE>>, + iomem: DevresIoMem<TH1520_PWM_REG_SIZE>, clk: Clk, } diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs index fc2a3e24f8d5..4691a01a3cf7 100644 --- a/rust/kernel/io/mem.rs +++ b/rust/kernel/io/mem.rs @@ -9,7 +9,7 @@ Bound, Device, // }, - devres::Devres, + devres::DevresLt, io::{ self, resource::{ @@ -20,6 +20,10 @@ MmioRaw, // }, prelude::*, + types::{ + CovariantForLt, + ForLt, // + }, }; /// An IO request for a specific device and resource. @@ -172,6 +176,19 @@ pub struct ExclusiveIoMem<'a, const SIZE: usize> { _region: Region, } +impl<const SIZE: usize> ForLt for ExclusiveIoMem<'static, SIZE> { + type Of<'a> = ExclusiveIoMem<'a, SIZE>; +} + +// SAFETY: `ExclusiveIoMem<'a, SIZE>` is covariant over `'a`; it holds an `IoMem<'a, SIZE>`, +// which holds `&'a Device<Bound>`, which is covariant. +unsafe impl<const SIZE: usize> CovariantForLt for ExclusiveIoMem<'static, SIZE> {} + +/// A device-managed exclusive I/O memory region. +/// +/// See [`ExclusiveIoMem::into_devres`]. +pub type DevresExclusiveIoMem<const SIZE: usize> = DevresLt<ExclusiveIoMem<'static, SIZE>>; + impl<'a, const SIZE: usize> ExclusiveIoMem<'a, SIZE> { /// Creates a new `ExclusiveIoMem` instance. fn ioremap(dev: &'a Device<Bound>, resource: &Resource) -> Result<Self> { @@ -198,15 +215,13 @@ fn ioremap(dev: &'a Device<Bound>, resource: &Resource) -> Result<Self> { /// Consume the `ExclusiveIoMem` and register it as a device-managed resource. /// - /// The returned `Devres<ExclusiveIoMem<'static, SIZE>>` can outlive the original lifetime - /// `'a`. Access to the I/O memory is revoked when the device is unbound. - pub fn into_devres(self) -> Result<Devres<ExclusiveIoMem<'static, SIZE>>> { - // SAFETY: Casting to `'static` is sound because `Devres` guarantees the - // `ExclusiveIoMem` does not actually outlive the device -- access is revoked and the - // resource is released when the device is unbound. - let iomem: ExclusiveIoMem<'static, SIZE> = unsafe { core::mem::transmute(self) }; - let dev = iomem.iomem.dev; - Devres::new(dev, iomem) + /// The returned [`DevresExclusiveIoMem`] can outlive the original borrow and be stored in + /// driver data. Access to the I/O memory is revoked automatically when the device is unbound. + pub fn into_devres(self) -> Result<DevresExclusiveIoMem<SIZE>> { + let dev = self.iomem.dev; + // SAFETY: `ExclusiveIoMem` only holds a device reference and an I/O mapping, both of + // which remain valid for the device's full bound scope, not just for `'a`. + unsafe { DevresLt::new(dev, self) } } } @@ -232,6 +247,19 @@ pub struct IoMem<'a, const SIZE: usize = 0> { io: MmioRaw<SIZE>, } +impl<const SIZE: usize> ForLt for IoMem<'static, SIZE> { + type Of<'a> = IoMem<'a, SIZE>; +} + +// SAFETY: `IoMem<'a, SIZE>` is covariant over `'a`; it holds `&'a Device<Bound>`, +// which is covariant. +unsafe impl<const SIZE: usize> CovariantForLt for IoMem<'static, SIZE> {} + +/// A device-managed I/O memory region. +/// +/// See [`IoMem::into_devres`]. +pub type DevresIoMem<const SIZE: usize> = DevresLt<IoMem<'static, SIZE>>; + impl<'a, const SIZE: usize> IoMem<'a, SIZE> { fn ioremap(dev: &'a Device<Bound>, resource: &Resource) -> Result<Self> { // Note: Some ioremap() implementations use types that depend on the CPU @@ -271,16 +299,13 @@ fn ioremap(dev: &'a Device<Bound>, resource: &Resource) -> Result<Self> { /// Consume the `IoMem` and register it as a device-managed resource. /// - /// The returned `Devres<IoMem<'static, SIZE>>` can outlive the original - /// lifetime `'a`. Access to the I/O memory is revoked when the device - /// is unbound. - pub fn into_devres(self) -> Result<Devres<IoMem<'static, SIZE>>> { - // SAFETY: Casting to `'static` is sound because `Devres` guarantees the `IoMem` does not - // actually outlive the device -- access is revoked and the resource is released when the - // device is unbound. - let iomem: IoMem<'static, SIZE> = unsafe { core::mem::transmute(self) }; - let dev = iomem.dev; - Devres::new(dev, iomem) + /// The returned [`DevresIoMem`] can outlive the original borrow and be stored in driver data. + /// Access to the I/O memory is revoked automatically when the device is unbound. + pub fn into_devres(self) -> Result<DevresIoMem<SIZE>> { + let dev = self.dev; + // SAFETY: `IoMem` only holds a device reference and an I/O mapping, both of which + // remain valid for the device's full bound scope, not just for `'a`. + unsafe { DevresLt::new(dev, self) } } } -- 2.54.0
