Re: [PATCH v2 4/4] rust: serdev: remove `serdev::Timeout`

[Markus Probst]

On Sat, 2026-07-18 at 16:02 +0100, Gary Guo wrote:
> On Sat Jul 18, 2026 at 1:47 PM BST, Markus Probst wrote:
> > Instead of relying on its own timeout types, the abstraction should make
> > use of `impl Into<Jiffies>`.
> > 
> > Suggested-by: Gary Guo <gary@xxxxxxxxxxx>
> > Link: https://lore.kernel.org/rust-for-linux/DK0SX3P5K1J6.1OV4ETJMXW83R@xxxxxxxxxxx/
> > Signed-off-by: Markus Probst <markus.probst@xxxxxxxxx>
> > ---
> >  rust/kernel/serdev.rs | 55 +++++++++++++++++----------------------------------
> >  1 file changed, 18 insertions(+), 37 deletions(-)
> > 
> > diff --git a/rust/kernel/serdev.rs b/rust/kernel/serdev.rs
> > index a78dfa6e2c27..0fdb37cff15d 100644
> > --- a/rust/kernel/serdev.rs
> > +++ b/rust/kernel/serdev.rs
> > @@ -20,11 +20,7 @@
> >          aref::AlwaysRefCounted,
> >          Mutex, //
> >      },
> > -    time::{
> > -        msecs_to_jiffies,
> > -        Jiffies,
> > -        Msecs, //
> > -    },
> > +    time::Jiffies,
> >      types::{
> >          Opaque,
> >          ScopeGuard, //
> > @@ -35,7 +31,6 @@
> >      cell::UnsafeCell,
> >      marker::PhantomData,
> >      mem::{offset_of, MaybeUninit},
> > -    num::NonZero,
> >      ptr::NonNull, //
> >  };
> >  
> > @@ -50,30 +45,6 @@ pub enum Parity {
> >      Odd = bindings::serdev_parity_SERDEV_PARITY_ODD,
> >  }
> >  
> > -/// Timeout in Jiffies.
> > -pub enum Timeout {
> > -    /// Wait for a specific amount of [`Jiffies`].
> > -    Jiffies(NonZero<Jiffies>),
> > -    /// Wait for a specific amount of [`Msecs`].
> > -    Milliseconds(NonZero<Msecs>),
> > -    /// Wait as long as possible.
> > -    ///
> > -    /// This is equivalent to [`kernel::task::MAX_SCHEDULE_TIMEOUT`].
> > -    Max,
> > -}
> > -
> > -impl Timeout {
> > -    fn into_jiffies(self) -> isize {
> > -        match self {
> > -            Self::Jiffies(value) => value.get().try_into().unwrap_or_default(),
> > -            Self::Milliseconds(value) => {
> > -                msecs_to_jiffies(value.get()).try_into().unwrap_or_default()
> > -            }
> > -            Self::Max => 0,
> > -        }
> > -    }
> > -}
> > -
> >  /// An adapter for the registration of serial device bus device drivers.
> >  pub struct Adapter<T: Driver>(T);
> >  
> > @@ -379,7 +350,7 @@ macro_rules! module_serdev_device_driver {
> >  ///         _id_info: Option<&'bound Self::IdInfo>,
> >  ///     ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
> >  ///         sdev.set_baudrate(115200);
> > -///         sdev.write_all(b"Hello\n", serdev::Timeout::Max)?;
> > +///         sdev.write_all(b"Hello\n", 0usize)?;
> 
> Note that the jiffies type is being converted to a new type (in fact,
> `Into<Jiffies>` only make sense with it being a new type.
I assume it won't take long for the patch series for the new type to be
merged. Currently there is no user for any other timeout than 0 (which
corrosponds to MAX_SCHEDULE_TIMEOUT in serdev).

Or should I revert to `serdev::Timeout` until then?

Thanks
- Markus Probst

> 
> Best,
> Gary
> 
> >  ///         Ok(MyDriver)
> >  ///     }
> >  /// }
> > @@ -505,11 +476,13 @@ pub fn set_parity(&self, parity: Parity) -> Result {
> >      /// [`Device::wait_until_sent`] to make sure the controller write buffer has actually been
> >      /// emptied.
> >      ///
> > +    /// Use a timeout of 0 to wait indefinitely.
> > +    ///
> >      /// Returns the number of bytes written (less than `data.len()` if interrupted).
> >      /// [`kernel::error::code::ETIMEDOUT`] or [`kernel::error::code::ERESTARTSYS`] if interrupted
> > -    /// before any bytes were written.
> > +    /// before any bytes were written. [`kernel::error::code::EINVAL`] if `data.len() > i32::MAX`.
> >      #[inline]
> > -    pub fn write_all(&self, data: &[u8], timeout: Timeout) -> Result<usize> {
> > +    pub fn write_all(&self, data: &[u8], timeout: impl Into<Jiffies>) -> Result<usize> {
> >          if data.len() > i32::MAX as usize {
> >              return Err(EINVAL);
> >          }
> > @@ -523,7 +496,7 @@ pub fn write_all(&self, data: &[u8], timeout: Timeout) -> Result<usize> {
> >                  self.as_raw(),
> >                  data.as_ptr(),
> >                  data.len(),
> > -                timeout.into_jiffies(),
> > +                isize::try_from(timeout.into()).unwrap_or_default(),
> >              )
> >          };
> >          // CAST: negative return values are guaranteed to be between `-MAX_ERRNO` and `-1`,
> > @@ -570,11 +543,19 @@ pub fn write_flush(&self) {
> >  
> >      /// Wait for the data to be sent.
> >      ///
> > -    /// After this function, the write buffer of the controller should be empty.
> > +    /// After this function, the write buffer of the controller should be empty or the timeout
> > +    /// elapsed.
> > +    ///
> > +    /// Use a timeout of 0 to wait indefinitely.
> >      #[inline]
> > -    pub fn wait_until_sent(&self, timeout: Timeout) {
> > +    pub fn wait_until_sent(&self, timeout: impl Into<Jiffies>) {
> >          // SAFETY: `self.as_raw()` is guaranteed to be a pointer to a valid `serdev_device`.
> > -        unsafe { bindings::serdev_device_wait_until_sent(self.as_raw(), timeout.into_jiffies()) };
> > +        unsafe {
> > +            bindings::serdev_device_wait_until_sent(
> > +                self.as_raw(),
> > +                isize::try_from(timeout.into()).unwrap_or_default(),
> > +            )
> > +        };
> >      }
> >  }
> >  
>

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