When Rust Binder assigns a new ID, it performs various fallible
operations before it "commits" to actually using the new ID. To support
this pattern, change acquire_next_id() so that it does not immediately
call set_bit(), but instead returns an object that may be used to call
set_bit() later.
The UnusedId type holds a exclusive reference to the IdPool, so it's
guaranteed that nobody else can call find_unused_id() while the UnusedId
object is live.
[Miguel: rust: id_pool: fix example]
Reviewed-by: Burak Emir <bqe@google.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Rust Binder wants to use inline bitmaps whenever possible to avoid
allocations, so introduce a constructor for an IdPool with arbitrary
capacity that stores the bitmap inline.
The existing constructor could be renamed to with_capacity() to match
constructors for other similar types, but it is removed as there is
currently no user for it.
[Miguel: rust: id_pool: fix broken intra-doc link]
Acked-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: Burak Emir <bqe@google.com>
Reviewed-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
We want to change ::new() to take no parameters and produce a pool that
is as large as possible while also being inline because that is the
constructor that Rust Binder actually needs.
However, to avoid complications in examples, we still need the current
constructor. So rename it to with_capacity(), which is the idiomatic
Rust name for this kind constructor.
Reviewed-by: Burak Emir <bqe@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
To avoid hard-coding these values in drivers, define constants for them
that drivers can reference. Also, update all instances in bitmap.rs and
id_pool.rs that use these values to use the new constants.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Burak Emir <bqe@google.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
This is a port of the Binder data structure introduced in commit
15d9da3f81 ("binder: use bitmap for faster descriptor lookup") to
Rust.
Like drivers/android/dbitmap.h, the ID pool abstraction lets
clients acquire and release IDs. The implementation uses a bitmap to
know what IDs are in use, and gives clients fine-grained control over
the time of allocation. This fine-grained control is needed in the
Android Binder. We provide an example that release a spinlock for
allocation and unit tests (rustdoc examples).
The implementation does not permit shrinking below capacity below
BITS_PER_LONG.
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Suggested-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Burak Emir <bqe@google.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
