rust: add Hardware Random Number Generator subsystem

[m-falkowski1]

This patch adds abstractions over the hwrng subsystem:

• trait hwrng::Operations that defines operations of a hwrng driver.
• declare_hwrng_operations!() macro that populates callback pointers
  located in hwrng structure.
• Registration structure for hwrng's drivers.

This patch is a dependency of a Samsung Exynos trng driver provided initially in #554.

Changes v5 -> v6:

• Replaced &'static CStr in favor of CString to support names created at runtime,
• Safety comment fixes rust: add Hardware Random Number Generator subsystem #592 (comment),
• Applied type inference as *const core::ffi::c_void -> as *const _. rust: add Hardware Random Number Generator subsystem #592 (comment),
• core::ffi:c_void -> c_types::c_void, rust: add Hardware Random Number Generator subsystem #592 (comment),
• Replaced [i8] with [u8].

Changes v4 -> v5:

• Added SPDX license identifier rust: add Hardware Random Number Generator subsystem #592 (comment),
• Removed dependency of hwrng::Operations::Data on Self (replaced with ()) and added Sync and Send requirements,
  Removed Sized + 'static requirements for hwrng::Operations rust: add Hardware Random Number Generator subsystem #592 (comment),
• ScopeGuard uses properly T::Data::from_pointer() method rust: add Hardware Random Number Generator subsystem #592 (comment),
• <T::Data as PointerWrapper>::into_pointer(data) => data.into_pointer() rust: add Hardware Random Number Generator subsystem #592 (comment),
• Added 'static to &CStr rust: add Hardware Random Number Generator subsystem #592 (comment),
• Implemented cleanup of T::Data in cleanup callback. T::Data is moved to the callback and
  Send is implemented for T::Data rust: add Hardware Random Number Generator subsystem #592 (comment),
• Callbacks moved to impl Registration rust: add Hardware Random Number Generator subsystem #592 (comment),
• Added #[allow(clippy::needless_update)] rust: add Hardware Random Number Generator subsystem #592 (comment),
• _p: PhantomData::default() => _p: PhantomData, rust: add Hardware Random Number Generator subsystem #592 (comment),
• Implemented Send trait for hwrng::Registration that
  has additional #[allow(clippy::non_send_fields_in_send_ty)] (see 334eb69).

Changes v3 -> v4:

• Added missing safety comments
• Deleted unnecessary clone of &CStr reference.

Changes v2 -> v3:

• Changed register() method so it now accepts self: Pin<&mut Self>. rust: add Hardware Random Number Generator subsystem #592 (comment)
• &mut *self.hwrng.get() -> self.hwrng.get(). rust: add Hardware Random Number Generator subsystem #592 (comment)
• Changed file name hw_random.rs -> hwrng.rs. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Changed HwrngOperations into hwrng::Operations. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Removed lifetime in a name parameter: name: &'a CStr -> name: &CStr. rust: add Hardware Random Number Generator subsystem #592 (comment)
• register() function makes a copy of the name argument. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Added new() and register() as public methods of Registration<T>. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Added ScopeGuard to prevent leaking registration state on failure. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Init of bindings::hwrng is done after the structure is pinned. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Used to_result() method instead of checking error code explicitly. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Added new boolean field registered to Registration<T> to check if driver was registered
  in Drop implementation.
• Changed returned type of read method in hwrng::Operations to unsigned. rust: add Hardware Random Number Generator subsystem #592 (comment)
• Typo & docs fixes.

Changes v1 (#554) -> v2:

• Removed unneded prefix _ in trait's method declaration Add Samsung Exynos true random number generator driver #554 (comment)
• Ported to use generic associated types from PR: Use generic associated types (GATs) to implement PointerWrapper. #556
• Various documentation fixes.

Signed-off-by: Maciej Falkowski [email protected]

[m-falkowski1]

The new version has just been uploaded. Feel free to review.

[m-falkowski1]

v5 posted.

[m-falkowski1]

CI failes somehow randomly on arm64 run. On my local repo CI completes correctly https://github.com/m-falkowski1/linux/actions/runs/1813535226. The same thing applies to the other patch I posted today.

[ojeda]

Yeah, there are a couple intermittent issues with the CI since the move to containers; I am taking a look. Meanwhile, I will rerun the CI for you.

[ojeda]

The arm64 issue, which was the prevalent one, is solved now.

[m-falkowski1]

That went quickly, I just saw #667, thanks!

[m-falkowski1]

v6 posted.

[m-falkowski1]

misc fix for v6.

[wedsonaf]

Very nice, thanks for putting this together!