Bounded Registers
Overview
A high-assurance memory-mapped register code generation and interaction library.
Getting Started
$ git clone git@github.com:auxoncorp/registers.git
$ cd registers && cargo install
Usage
The macro
register!
The register!
macro generates the code necessary for ergonomic
register access and manipulation. The expected input for the macro is
as follows:
- The register name.
- Its numeric type.
- Its mode, either
RO
(read only),RW
(read write), orWO
(write only). - The register's fields, beginning with
Fields [
, and then a closing]
at the end.
A field constists of its name, its width, and its offset within the
register. Optionally, one may also state enum-like key/value pairs for
the values of the field, nested within the field declaration with
[]
's
The code which this macro generates is a tree of nested modules where
the root is a module called $register_name
. Within $register_name
,
there will be the register itself, as $register_name::Register
, as
well as a child module for each field.
Within each field module, one can find the field itself, as
$register_name::$field_name::Field
, as well as a few helpful aliases
and constants.
$register_name::$field_name::Read
: In order to read a field, an instance of that field must be given to have access to its mask and offset.Read
can be used as an argument toget_field
so one does not have to construct an arbitrary one when doing a read.$register_name::$field_name::Clear
: A field whose value is zero. Passing it tomodify
will clear that field in the register.$register_name::$field_name::Set
: A field whose value is$field_max
. Passing it tomodify
will set that field to its max value in the register. This is useful particularly in the case of single-bit wide fields.$register_name::$field_name::$enum_kvs
: constants mapping the enum like field names to values.
Interacting with registers
Through a constructor
In this example, we initialize a register with the value 0
and then
set the Dead
bit—the second field—which should produce the value 2
when interpreting this word-sized register as a u32
.
Through a register block
Here we take a known address, one we may find in a developer's manual, and interpret that address as a register block. We can then dereference that pointer and use the register API to access the registers in the block.
register!
register!
register!
You can then implement Deref
and DerefMut
for a type which holds
onto the address of such a register block. This fills in the gaps for
method lookup (during typechecking) so that you can ergonomically use
this type to interact with the register block:
The Register API
The register API code is generated with docs, but you'll have to build
the rustdoc documentation for your library that uses
bounded-registers
to be able to see it. For convenience, I've
extrapolated it here:
Theory
bounded-registers
employs values—specifically numbers—at the type-level in
order to get compile time assertions on interactions with a
register. Each field's width is used to determine a maximum value, and
then reading from and writing to those fields is either checked at
compile time, through the checked
function, or is expected to
/carry/ a proof, which uses the aforementioned bound to construct a
value at runtime which is known to not contravene it.
License
bounded-registers
is licensed under the MIT License (MIT) unless
otherwise noted. Please see LICENSE for more details.