document #[app]

1 files changed, 188 insertions, 0 deletions

diff --git a/macros/src/lib.rs b/macros/src/lib.rs
index 7a436e7b..6675765b 100644
--- a/macros/src/lib.rs
+++ b/macros/src/lib.rs
@@ -13,6 +13,194 @@ mod codegen;
 #[cfg(test)]
 mod tests;
 
+/// Attribute used to declare a RTFM application
+///
+/// This attribute must be applied to a `const` item of type `()`. The `const` item is effectively
+/// used as a `mod` item: its value must be a block that contains items commonly found in modules,
+/// like functions and `static` variables.
+///
+/// The `app` attribute has one mandatory argument:
+///
+/// - `device = <path>`. The path must point to a device crate generated using [`svd2rust`]
+/// **v0.14.x**.
+///
+/// [`svd2rust`]: https://crates.io/crates/svd2rust
+///
+/// and several optional arguments:
+///
+/// - `peripherals = <bool>`. Indicates whether the runtime takes the device peripherals and makes
+/// them available to the `init` context.
+///
+/// - `monotonic = <path>`. This is a path to a zero-sized structure (e.g. `struct Foo;`) that
+/// implements the `Monotonic` trait. This argument must be provided to use the `schedule` API.
+///
+/// The items allowed in the block value of the `const` item are specified below:
+///
+/// # 1. `struct Resources`
+///
+/// This structure contains the declaration of all the resources used by the application. Each field
+/// in this structure corresponds to a different resource. Each resource may optionally be given an
+/// initial value using the `#[init(<value>)]` attribute. Resources with no compile-time initial
+/// value as referred to as *late* resources.
+///
+/// # 2. `fn`
+///
+/// Functions must contain *one* of the following attributes: `init`, `idle` or `task`. The
+/// attribute defines the role of the function in the application.
+///
+/// ## a. `#[init]`
+///
+/// This attribute indicates that the function is to be used as the *initialization function*. There
+/// must be exactly one instance of the `init` attribute inside the `app` pseudo-module. The
+/// signature of the `init` function must be `fn (<fn-name>::Context) [-> <fn-name>::LateResources]`
+/// where `<fn-name>` is the name of the function adorned with the `#[init]` attribute.
+///
+/// The `init` function runs after memory (RAM) is initialized and runs with interrupts disabled.
+/// Interrupts are re-enabled after `init` returns.
+///
+/// The `init` attribute accepts the following optional arguments:
+///
+/// - `resources = [resource_a, resource_b, ..]`. This is the list of resources this context has
+/// access to.
+///
+/// - `schedule = [task_a, task_b, ..]`. This is the list of *software* tasks that this context can
+/// schedule to run in the future. *IMPORTANT*: This argument is accepted only if the `monotonic`
+/// argument is passed to the `#[app]` attribute.
+///
+/// - `spawn = [task_a, task_b, ..]`. This is the list of *software* tasks that this context can
+/// immediately spawn.
+///
+/// The first argument of the function, `<fn-name>::Context`, is a structure that contains the
+/// following fields:
+///
+/// - `core`. Exclusive access to core peripherals. The type of this field is [`rtfm::Peripherals`]
+/// when the `schedule` API is used and [`cortex_m::Peripherals`] when it's not.
+///
+/// [`rtfm::Peripherals`]: ../rtfm/struct.Peripherals.html
+/// [`cortex_m::Peripherals`]: https://docs.rs/cortex-m/0.6/cortex_m/peripheral/struct.Peripherals.html
+///
+/// - `device: <device>::Peripherals`. Exclusive access to device-specific peripherals. This
+/// field is only present when the `peripherals` argument of the `#[app]` attribute is set to
+/// `true`. `<device>` is the path to the device crate specified in the top `app` attribute.
+///
+/// - `start: <Instant>`. The `start` time of the system: `<Instant>::zero()`. `<Instant>` is the
+/// `Instant` type associated to the `Monotonic` implementation specified in the top `#[app]`
+/// attribute. **NOTE**: this field is only present when the `schedule` is used.
+///
+/// - `resources: <fn-name>::Resources`. A `struct` that contains all the resources that can be
+/// accessed from this context. Each field is a different resource; each resource may appear as a
+/// reference (`&[mut]-`) or as proxy structure that implements the [`rftm::Mutex`] trait.
+///
+/// [`rtfm::Mutex`]: ../rtfm/trait.Mutex.html
+///
+/// - `schedule: <fn-name>::Schedule`. A `struct` that can be used to schedule *software* tasks.
+///
+/// - `spawn: <fn-name>::Spawn`. A `struct` that can be used to spawn *software* tasks.
+///
+/// The return type `<fn-name>::LateResources` must only be specified when late resources, resources
+/// with no initial value declared at compile time, are used. `<fn-name>::LateResources` is a
+/// structure where each field corresponds to a different late resource. The
+/// `<fn-name>::LateResources` value returned by the `#[init]` function is used to initialize the
+/// late resources before `idle` or any task can start.
+///
+/// Other properties:
+///
+/// - The `static mut` variables declared at the beginning of this function will be transformed into
+/// `&'static mut` references that are safe to access. For example, `static mut FOO: u32 = 0` will
+/// become `FOO: &'static mut u32`.
+///
+/// ## b. `#[idle]`
+///
+/// This attribute indicates that the function is to be used as the *idle task*. There can be at
+/// most once instance of the `idle` attribute inside the `app` pseudo-module. The signature of the
+/// `idle` function must be `fn(<fn-name>::Context) -> !` where `<fn-name>` is the name of the
+/// function adorned with the `#[idle]` attribute.
+///
+/// The `idle` task is a special task that always runs in the background. The `idle` task runs at
+/// the lowest priority of `0`. If the `idle` task is not defined then the runtime sets the
+/// [SLEEPONEXIT] bit after executing `init`.
+///
+/// [SLEEPONEXIT]: https://developer.arm.com/products/architecture/cpu-architecture/m-profile/docs/100737/0100/power-management/sleep-mode/sleep-on-exit-bit
+///
+/// The `idle` attribute accepts the following optional arguments:
+///
+/// - `resources = (..)`. Same meaning / function as [`#[init].resources`](#a-init).
+///
+/// - `schedule = (..)`. Same meaning / function as [`#[init].schedule`](#a-init).
+///
+/// - `spawn = (..)`. Same meaning / function as [`#[init].spawn`](#a-init).
+///
+/// The first argument of the function, `idle::Context`, is a structure that contains the following
+/// fields:
+///
+/// - `resources: _`. Same meaning / function as [`<init>::Context.resources`](#a-init).
+///
+/// - `schedule: idle::Schedule`. Same meaning / function as [`<init>::Context.schedule`](#a-init).
+///
+/// - `spawn: idle::Spawn`. Same meaning / function as [`<init>::Context.spawn`](#a-init).
+///
+/// Other properties:
+///
+/// - The `static mut` variables declared at the beginning of this function will be transformed into
+/// `&'static mut` references that are safe to access. For example, `static mut FOO: u32 = 0` will
+/// become `FOO: &'static mut u32`.
+///
+/// ## c. `#[task]`
+///
+/// This attribute indicates that the function is either a hardware task or a software task. The
+/// signature of hardware tasks must be `fn(<fn-name>::Context)` whereas the signature of software
+/// tasks must be `fn(<fn-name>::Context, <inputs>)`. `<fn-name>` refers to the name of the function
+/// adorned with the `#[task]` attribute.
+///
+/// The `task` attribute accepts the following optional arguments.
+///
+/// - `binds = <interrupt-name>`. Binds this task to a particular interrupt. When this argument is
+/// present the task is treated as a hardware task; when it's omitted the task treated is treated as
+/// a software task.
+///
+/// - `priority = <integer>`. This is the static priority of the exception handler. The value must
+/// be in the range `1..=(1 << <device-path>::NVIC_PRIO_BITS)` where `<device-path>` is the path to
+/// the device crate specified in the top `app` attribute. If this argument is omitted the priority
+/// is assumed to be 1.
+///
+/// - `resources = (..)`. Same meaning / function as [`#[init].resources`](#a-init).
+///
+/// - `schedule = (..)`. Same meaning / function as [`#[init].schedule`](#a-init).
+///
+/// - `spawn = (..)`. Same meaning / function as [`#[init].spawn`](#a-init).
+///
+/// The first argument of the function, `<fn-name>::Context`, is a structure that contains the
+/// following fields:
+///
+/// - `start: <Instant>`. For hardware tasks this is the time at which this handler started
+/// executing. For software tasks this is the time at which the task was scheduled to run. **NOTE**:
+/// only present when the `schedule` API is used.
+///
+/// - `resources: _`. Same meaning / function as [`<init>::Context.resources`](#a-init).
+///
+/// - `schedule: <exception-name>::Schedule`. Same meaning / function as
+/// [`<init>::Context.schedule`](#a-init).
+///
+/// - `spawn: <exception-name>::Spawn`.  Same meaning / function as
+/// [`<init>::Context.spawn`](#a-init).
+///
+/// Other properties / constraints:
+///
+/// - The `static mut` variables declared at the beginning of this function will be transformed into
+/// *non*-static `&mut` references that are safe to access. For example, `static mut FOO: u32 = 0`
+/// will become `FOO: &mut u32`.
+///
+/// # 3. `extern` block
+///
+/// This `extern` block contains a list of interrupts which are *not* used by the application as
+/// hardware tasks. These interrupts will be used to dispatch software tasks. Each interrupt will be
+/// used to dispatch *multiple* software tasks *at the same priority level*.
+///
+/// This `extern` block must only contain functions with signature `fn ()`. The names of these
+/// functions must match the names of the target device interrupts.
+///
+/// Attributes can be applied to the functions inside this block. These attributes will be forwarded
+/// to the interrupt handlers generated by the `app` attribute.
 #[proc_macro_attribute]
 pub fn app(args: TokenStream, input: TokenStream) -> TokenStream {
     let mut settings = Settings::default();