Add read_poll_count_atomic function which polls periodically until a
condition is met, an error occurs, or the attempt limit is reached.

This helper is used to wait for a condition in atomic context,
mirroring the C's read_poll_timeout_atomic().

In atomic context, the timekeeping infrastructure is unavailable, so
reliable time-based timeouts cannot be implemented. So instead, the
helper accepts a maximum number of attempts and busy-waits (udelay +
cpu_relax) between tries.

v1: https://lore.kernel.org/lkml/20250821035710.3692455-1-fujita.tomonori@gmail.com/
- use the attempt limit instead of timeout
- rename the function to read_poll_count_atomic
- add the comment about C's udelay behavior.


FUJITA Tomonori (2):
  rust: add udelay() function
  rust: Add read_poll_count_atomic function

 rust/helpers/time.c       |  5 +++
 rust/kernel/io/poll.rs    | 80 ++++++++++++++++++++++++++++++++++++++-
 rust/kernel/time/delay.rs | 37 ++++++++++++++++++
 3 files changed, 121 insertions(+), 1 deletion(-)


base-commit: e6901808a3b28d8bdabfa98a618b2eab6f8798e8
-- 
2.43.0