rust: Add IO polling

Add two new types, Instant and Delta, which represent a specific point
in time and a span of time, respectively, with Rust version of
fsleep().

I dropped patches related with read_poll_timeout() in this version,
which we haven't reached agreement on yet. There are other potential
uses for the Instant and Delta types, so it's better to upstream them
first. Note that I haven't changed the subject to avoid confusion.

Unlike the old rust time branch, this adds a wrapper for fsleep()
instead of msleep(). fsleep() automatically chooses the best sleep
method based on a duration.

v15
- fix the comment and commit message on Ktime
v14: https://lore.kernel.org/lkml/20250422135336.194579-1-fuji...
- rebased on timekeeping-next
- add Ktime type temporarily to hrtimer
v13: https://lore.kernel.org/lkml/20250413104310.162045-1-fuji...
- fix typo in MAINTAINERS file
v12: https://lore.kernel.org/lkml/20250406013445.124688-1-fuji...
- drop #1, #6, and #7 patches, which we haven't reached agreement on yet
- adjust hrtimer code to use Instance for the removal of Ktime
v11: https://lore.kernel.org/lkml/20250220070611.214262-1-fuji...
- use file_len arg name in __might_resched_precision() instead of len for clarity
- remove unnecessary strlen in __might_resched(); just use a large value for the precision
- add more doc and example for read_poll_timeout()
- fix read_poll_timeout() to call __might_sleep() only with CONFIG_DEBUG_ATOMIC_SLEEP enabled
- call might_sleep() instead of __might_sleep() in read_poll_timeout() to match the C version
- Add new sections for the abstractions in MAINTAINERS instead of adding rust files to the existing sections
v10: https://lore.kernel.org/lkml/20250207132623.168854-1-fuji...
- rebased on rust-next
- use Option type for timeout argument for read_poll_timeout()
- remove obsoleted comment on read_poll_timeout()
v9: https://lore.kernel.org/lkml/20250125101854.112261-1-fuji...
- make the might_sleep() changes into as a separate patch
- add as_millis() method to Delta for Binder driver
- make Delta's as_*() methods const (useful in some use cases)
- add Delta::ZERO const; used in fsleep()
- fix typos
- use intra-doc links
- place the #[inline] marker before the documentation
- remove Instant's from_raw() method
- add Invariants to Instant type
- improve Delta's methods documents
- fix fsleep() SAFETY comment
- improve fsleep() documents
- lift T:Copy restriction in read_poll_timeout()
- use MutFn for Cond in read_poll_timeout() instead of Fn
- fix might_sleep() call in read_poll_timeout()
- simplify read_poll_timeout() logic
v8: https://lore.kernel.org/lkml/20250116044100.80679-1-fujit...
- fix compile warnings
v7: https://lore.kernel.org/lkml/20241220061853.2782878-1-fuj...
- rebased on rust-next
- use crate::ffi instead of core::ffi
v6: https://lore.kernel.org/lkml/20241114070234.116329-1-fuji...
- use super::Delta in delay.rs
- improve the comments
- add Delta's is_negative() method
- rename processor.rs to cpu.rs for cpu_relax()
- add __might_sleep_precision() taking pointer to a string with the length
- implement read_poll_timeout as normal function instead of macro
v5: https://lore.kernel.org/lkml/20241101010121.69221-1-fujit...
- set the range of Delta for fsleep function
- update comments
v4: https://lore.kernel.org/lkml/20241025033118.44452-1-fujit...
- rebase on the tip tree's timers/core
- add Instant instead of using Ktime
- remove unused basic methods
- add Delta as_micros_ceil method
- use const fn for Delta from_* methods
- add more comments based on the feedback
- add a safe wrapper for cpu_relax()
- add __might_sleep() macro
v3: https://lore.kernel.org/lkml/20241016035214.2229-1-fujita...
- Update time::Delta methods (use i64 for everything)
- Fix read_poll_timeout to show the proper debug info (file and line)
- Move fsleep to rust/kernel/time/delay.rs
- Round up delta for fsleep
- Access directly ktime_t instead of using ktime APIs
- Add Eq and Ord with PartialEq and PartialOrd
v2: https://lore.kernel.org/lkml/20241005122531.20298-1-fujit...
- Introduce time::Delta instead of core::time::Duration
- Add some trait to Ktime for calculating timeout
- Use read_poll_timeout in QT2025 driver instead of using fsleep directly
v1: https://lore.kernel.org/netdev/20241001112512.4861-1-fuji...

FUJITA Tomonori (6):
  rust: hrtimer: Add Ktime temporarily
  rust: time: Add PartialEq/Eq/PartialOrd/Ord trait to Ktime
  rust: time: Introduce Delta type
  rust: time: Introduce Instant type
  rust: time: Add wrapper for fsleep() function
  MAINTAINERS: rust: Add a new section for all of the time stuff

 MAINTAINERS                         |  11 +-
 rust/helpers/helpers.c              |   1 +
 rust/helpers/time.c                 |   8 ++
 rust/kernel/time.rs                 | 168 +++++++++++++++++++++-------
 rust/kernel/time/delay.rs           |  49 ++++++++
 rust/kernel/time/hrtimer.rs         |  18 ++-
 rust/kernel/time/hrtimer/arc.rs     |   2 +-
 rust/kernel/time/hrtimer/pin.rs     |   2 +-
 rust/kernel/time/hrtimer/pin_mut.rs |   4 +-
 rust/kernel/time/hrtimer/tbox.rs    |   2 +-
 10 files changed, 216 insertions(+), 49 deletions(-)
 create mode 100644 rust/helpers/time.c
 create mode 100644 rust/kernel/time/delay.rs


base-commit: 8ffd015db85fea3e15a77027fda6c02ced4d2444
-- 
2.43.0