* [PATCH 1/2] rust: impl_flags: add conversion functions
2026-02-15 20:22 [PATCH 0/2] rust: impl_flags: add convenience functions Andreas Hindborg
@ 2026-02-15 20:22 ` Andreas Hindborg
2026-02-15 20:53 ` Miguel Ojeda
2026-02-15 20:22 ` [PATCH 2/2] rust: impl_flags: add bitwise operations with the underlying type Andreas Hindborg
2026-02-27 14:20 ` [PATCH 0/2] rust: impl_flags: add convenience functions Gary Guo
2 siblings, 1 reply; 6+ messages in thread
From: Andreas Hindborg @ 2026-02-15 20:22 UTC (permalink / raw)
To: Miguel Ojeda, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Alice Ryhl, Trevor Gross, Danilo Krummrich
Cc: rust-for-linux, linux-kernel, Andreas Hindborg
Add two conversion functions to the `impl_flags!` macro:
- A `From<_>` implementation to convert from the flag value enum to
underlying type.
- A `TryFrom<_> implementation to convert from the underlying
representation to flag container type.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/impl_flags.rs | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/rust/kernel/impl_flags.rs b/rust/kernel/impl_flags.rs
index 9160e8ce2e126..f34ecbe870d80 100644
--- a/rust/kernel/impl_flags.rs
+++ b/rust/kernel/impl_flags.rs
@@ -102,6 +102,26 @@ fn from(value: $flags) -> Self {
}
}
+ impl ::core::convert::From<$flag> for $ty {
+ #[inline]
+ fn from(value: $flag) -> Self {
+ // SAFETY: All `$flag` values are valid for use as `$ty`.
+ unsafe { core::mem::transmute::<$flag, $ty>(value) }
+ }
+ }
+
+ impl ::core::convert::TryFrom<$ty> for $flags {
+ type Error = ::kernel::error::Error;
+
+ fn try_from(value: $ty) -> Result<Self, Self::Error> {
+ match value & !$flags::all_bits() == 0 {
+ // SAFETY: We checked above that `value` is a valid bit pattern for `$flags`.
+ true => Ok(unsafe {::core::mem::transmute::<$ty, $flags>(value)}),
+ false => Err(::kernel::error::code::EINVAL),
+ }
+ }
+ }
+
impl ::core::ops::BitOr for $flags {
type Output = Self;
#[inline]
--
2.51.2
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 1/2] rust: impl_flags: add conversion functions
2026-02-15 20:22 ` [PATCH 1/2] rust: impl_flags: add conversion functions Andreas Hindborg
@ 2026-02-15 20:53 ` Miguel Ojeda
2026-05-12 8:05 ` Andreas Hindborg
0 siblings, 1 reply; 6+ messages in thread
From: Miguel Ojeda @ 2026-02-15 20:53 UTC (permalink / raw)
To: Andreas Hindborg
Cc: Miguel Ojeda, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Alice Ryhl, Trevor Gross, Danilo Krummrich,
rust-for-linux, linux-kernel
On Sun, Feb 15, 2026 at 9:23 PM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
> + impl ::core::convert::From<$flag> for $ty {
> + #[inline]
> + fn from(value: $flag) -> Self {
> + // SAFETY: All `$flag` values are valid for use as `$ty`.
> + unsafe { core::mem::transmute::<$flag, $ty>(value) }
> + }
> + }
Why do we need the transmute instead of a cast? Did you notice a difference?
Same in the other one -- why not constructing the object normally?
Also, you can use `Self` for `$ty` and `$flags` to make it easier to read.
In addition, I would suggest an early return with a simple `if`.
Finally, it wouldn't hurt adding a one-liner example for each at the top.
Thanks!
Cheers,
Miguel
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH 1/2] rust: impl_flags: add conversion functions
2026-02-15 20:53 ` Miguel Ojeda
@ 2026-05-12 8:05 ` Andreas Hindborg
0 siblings, 0 replies; 6+ messages in thread
From: Andreas Hindborg @ 2026-05-12 8:05 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Miguel Ojeda, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Alice Ryhl, Trevor Gross, Danilo Krummrich,
rust-for-linux, linux-kernel
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> writes:
> On Sun, Feb 15, 2026 at 9:23 PM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> + impl ::core::convert::From<$flag> for $ty {
>> + #[inline]
>> + fn from(value: $flag) -> Self {
>> + // SAFETY: All `$flag` values are valid for use as `$ty`.
>> + unsafe { core::mem::transmute::<$flag, $ty>(value) }
>> + }
>> + }
>
> Why do we need the transmute instead of a cast? Did you notice a difference?
No, I did not think of using `as`. I can do that.
> Same in the other one -- why not constructing the object normally?
Will do.
> Also, you can use `Self` for `$ty` and `$flags` to make it easier to read.
Ok.
>
> In addition, I would suggest an early return with a simple `if`.
Ok.
>
> Finally, it wouldn't hurt adding a one-liner example for each at the top.
I'll add an example.
Best regards,
Andreas Hindborg
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/2] rust: impl_flags: add bitwise operations with the underlying type
2026-02-15 20:22 [PATCH 0/2] rust: impl_flags: add convenience functions Andreas Hindborg
2026-02-15 20:22 ` [PATCH 1/2] rust: impl_flags: add conversion functions Andreas Hindborg
@ 2026-02-15 20:22 ` Andreas Hindborg
2026-02-27 14:20 ` [PATCH 0/2] rust: impl_flags: add convenience functions Gary Guo
2 siblings, 0 replies; 6+ messages in thread
From: Andreas Hindborg @ 2026-02-15 20:22 UTC (permalink / raw)
To: Miguel Ojeda, Boqun Feng, Gary Guo, Björn Roy Baron,
Benno Lossin, Alice Ryhl, Trevor Gross, Danilo Krummrich
Cc: rust-for-linux, linux-kernel, Andreas Hindborg
Add bitwise or operations between the flag value enum and the underlying
type. This is useful when manipulating flags from C API without round
tripping into the Rust flag container type:
let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() };
...
if self.write_cache {
lim.features |= request::Feature::WriteCache;
}
The above code would be needlessly verbose without this direct assignment
option.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/impl_flags.rs | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/rust/kernel/impl_flags.rs b/rust/kernel/impl_flags.rs
index f34ecbe870d80..f829be815885e 100644
--- a/rust/kernel/impl_flags.rs
+++ b/rust/kernel/impl_flags.rs
@@ -245,6 +245,22 @@ fn bitxor(self, rhs: $flag) -> Self::Output {
}
}
+ impl ::core::ops::BitOr<$flag> for $ty {
+ type Output = Self;
+
+ #[inline]
+ fn bitor(self, rhs: $flag) -> Self::Output {
+ self | <$flag as Into<Self>>::into(rhs)
+ }
+ }
+
+ impl ::core::ops::BitOrAssign<$flag> for $ty {
+ #[inline]
+ fn bitor_assign(&mut self, rhs: $flag) {
+ *self = *self | <$flag as Into<Self>>::into(rhs)
+ }
+ }
+
impl $flags {
/// Returns an empty instance of `type` where no flags are set.
#[inline]
--
2.51.2
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 0/2] rust: impl_flags: add convenience functions
2026-02-15 20:22 [PATCH 0/2] rust: impl_flags: add convenience functions Andreas Hindborg
2026-02-15 20:22 ` [PATCH 1/2] rust: impl_flags: add conversion functions Andreas Hindborg
2026-02-15 20:22 ` [PATCH 2/2] rust: impl_flags: add bitwise operations with the underlying type Andreas Hindborg
@ 2026-02-27 14:20 ` Gary Guo
2 siblings, 0 replies; 6+ messages in thread
From: Gary Guo @ 2026-02-27 14:20 UTC (permalink / raw)
To: Andreas Hindborg, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Alice Ryhl, Trevor Gross,
Danilo Krummrich
Cc: rust-for-linux, linux-kernel
On Sun Feb 15, 2026 at 8:22 PM GMT, Andreas Hindborg wrote:
> Add a few convenience functions that makes it easier to work with the
> `impl_flags` module and C APIs.
I am not sure that we want to encourage direct manipulation of the underlying
bits. Adding these impls would add a surface of misuse.
Best,
Gary
>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> Andreas Hindborg (2):
> rust: impl_flags: add conversion functions
> rust: impl_flags: add bitwise operations with the underlying type
>
> rust/kernel/impl_flags.rs | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
> ---
> base-commit: e9ec05addd1a067fc7cb218f20ecdc1b1b0898c0
> change-id: 20260215-impl-flags-additions-0340ffcba5b9
> prerequisite-change-id: 20250304-feat-add-bitmask-macro-6424b1c317e2:v8
> prerequisite-patch-id: 05dfcf648017dee65c356604e4f99959e76ff64d
> prerequisite-change-id: 20260212-impl-flags-inner-c61974b27b18:v1
> prerequisite-patch-id: edebc37750dccd8d19db0b8fbd5f69f9877675a2
>
> Best regards,
^ permalink raw reply [flat|nested] 6+ messages in thread