rust: soc: apple: Add Apple mailbox abstractions

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>

Author: WhatAmISupposedToPutHere

drivers/soc/apple/Kconfig

@@ -38,6 +38,12 @@ config APPLE_SART
 
 	  Say 'y' here if you have an Apple SoC.
 
+config RUST_APPLE_MAILBOX
+	bool
+	depends on PM
+	depends on RUST
+	select APPLE_MAILBOX
+
 config RUST_APPLE_RTKIT
 	bool
 	depends on PM

drivers/soc/apple/mailbox.c

@@ -28,9 +28,9 @@
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/soc/apple/mailbox.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
-#include "mailbox.h"
 
 #define APPLE_ASC_MBOX_CONTROL_FULL BIT(16)
 #define APPLE_ASC_MBOX_CONTROL_EMPTY BIT(17)

drivers/soc/apple/rtkit-internal.h

@@ -15,9 +15,9 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/soc/apple/mailbox.h>
 #include <linux/soc/apple/rtkit.h>
 #include <linux/workqueue.h>
-#include "mailbox.h"
 
 #define APPLE_RTKIT_APP_ENDPOINT_START 0x20
 #define APPLE_RTKIT_MAX_ENDPOINTS 0x100

drivers/soc/apple/mailbox.h include/linux/soc/apple/mailbox.hdrivers/soc/apple/mailbox.h renamed to include/linux/soc/apple/mailbox.h

@@ -85,6 +85,7 @@
 #include <linux/sched.h>
 #include <linux/security.h>
 #include <linux/slab.h>
+#include <linux/soc/apple/mailbox.h>
 #include <linux/soc/apple/rtkit.h>
 #include <linux/task_work.h>
 #include <linux/tracepoint.h>

rust/bindings/bindings_helper.h

@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+
+//! Support for Apple ASC Mailbox.
+//!
+//! C header: [`include/linux/soc/apple/mailbox.h`](../../../../include/linux/gpio/driver.h)
+
+use crate::{
+    bindings,
+    device,
+    error::{
+        from_err_ptr,
+        to_result, //
+    },
+    prelude::*,
+    str::CStrExt,
+    types::{
+        ForeignOwnable,
+        ScopeGuard, //
+    }, //
+};
+
+use core::marker::PhantomData;
+
+/// 96-bit message. What it means is up to the upper layer
+pub type Message = bindings::apple_mbox_msg;
+
+/// Mailbox receive callback
+pub trait MailCallback {
+    /// Callback context
+    type Data: ForeignOwnable + Send + Sync;
+
+    /// The actual callback. Called in an interrupt context.
+    fn recv_message(data: <Self::Data as ForeignOwnable>::Borrowed<'_>, msg: Message);
+}
+
+/// Wrapper over `struct apple_mbox *`
+#[repr(transparent)]
+pub struct Mailbox<T: MailCallback> {
+    mbox: *mut bindings::apple_mbox,
+    _p: PhantomData<T>,
+}
+
+extern "C" fn mailbox_rx_callback<T: MailCallback>(
+    _mbox: *mut bindings::apple_mbox,
+    msg: Message,
+    cookie: *mut crate::ffi::c_void,
+) {
+    // SAFETY: cookie came from a call to `into_foreign`
+    T::recv_message(unsafe { T::Data::borrow(cookie.cast()) }, msg);
+}
+
+impl<T: MailCallback> Mailbox<T> {
+    /// Creates a mailbox for the specified name.
+    pub fn new_byname(
+        dev: &device::Device,
+        mbox_name: &'static CStr,
+        data: T::Data,
+    ) -> Result<Mailbox<T>> {
+        let ptr: *mut crate::ffi::c_void = data.into_foreign().cast();
+        let guard = ScopeGuard::new(|| {
+            // SAFETY: `ptr` came from a previous call to `into_foreign`.
+            unsafe { T::Data::from_foreign(ptr.cast()) };
+        });
+        // SAFETY: Just calling the c function, all values are valid.
+        let mbox = unsafe {
+            from_err_ptr(bindings::apple_mbox_get_byname(
+                dev.as_raw(),
+                mbox_name.as_char_ptr(),
+            ))?
+        };
+        // SAFETY: mbox is a valid pointer
+        unsafe {
+            (*mbox).cookie = ptr;
+            (*mbox).rx = Some(mailbox_rx_callback::<T>);
+            to_result(bindings::apple_mbox_start(mbox))?;
+        }
+        guard.dismiss();
+        Ok(Mailbox {
+            mbox,
+            _p: PhantomData,
+        })
+    }
+    /// Sends the specified message
+    pub fn send(&self, msg: Message, atomic: bool) -> Result<()> {
+        // SAFETY: Calling the c function, `mbox` is a valid pointer
+        to_result(unsafe { bindings::apple_mbox_send(self.mbox, msg, atomic) })
+    }
+}
+
+impl<T: MailCallback> Drop for Mailbox<T> {
+    fn drop(&mut self) {
+        // SAFETY: mbox is a valid pointer
+        unsafe { bindings::apple_mbox_stop(self.mbox) };
+        // SAFETY: `cookie` came from `into_foreign`
+        unsafe { T::Data::from_foreign((*self.mbox).cookie.cast()) };
+    }
+}
+
+unsafe impl<T> Sync for Mailbox<T>
+where
+    T: MailCallback,
+    T::Data: Sync,
+{
+}
+
+unsafe impl<T> Send for Mailbox<T>
+where
+    T: MailCallback,
+    T::Data: Send,
+{
+}

rust/kernel/soc/apple/mailbox.rs

@@ -7,3 +7,6 @@ pub mod rtkit;
 
 #[cfg(any(CONFIG_APPLE_AOP = "y", CONFIG_APPLE_AOP = "m"))]
 pub mod aop;
+
+#[cfg(CONFIG_RUST_APPLE_MAILBOX = "y")]
+pub mod mailbox;