Merge #1917

1917: hil: ble_advertising: Pass the transmit buffer on callback r=ppannuto a=alistair23

### Pull Request Overview

Pass the BLE transmit buffer back to the capsule.

### Testing Strategy

### TODO or Help Wanted

### Documentation Updated

- [X] Updated the relevant files in `/docs`, or no updates are required.

### Formatting

- [X] Ran `make prepush`.


Co-authored-by: Alistair Francis <alistair@alistair23.me>

capsules/src/ble_advertising_driver.rs

@@ -265,10 +265,8 @@ impl App {
                     data[..adv_data_len].copy_from_slice(adv_data_corrected);
                 }
                 let total_len = cmp::min(PACKET_LENGTH, payload_len + 2);
-                let result = ble
-                    .radio
+                ble.radio
                     .transmit_advertisement(kernel_tx, total_len, channel);
-                ble.kernel_tx.replace(result);
                 ReturnCode::SUCCESS
             })
         })
@@ -507,7 +505,8 @@ where
 {
     // The ReturnCode indicates valid CRC or not, not used yet but could be used for
     // re-transmissions for invalid CRCs
-    fn transmit_event(&self, _crc_ok: ReturnCode) {
+    fn transmit_event(&self, buf: &'static mut [u8], _crc_ok: ReturnCode) {
+        self.kernel_tx.replace(buf);
         self.sending_app.map(|appid| {
             let _ = self.app.enter(*appid, |app, _| {
                 match app.process_status {

chips/nrf52/src/ble_radio.rs

@@ -36,6 +36,7 @@
 use core::cell::Cell;
 use core::convert::TryFrom;
 use kernel::common::cells::OptionalCell;
+use kernel::common::cells::TakeCell;
 use kernel::common::registers::{register_bitfields, ReadOnly, ReadWrite, WriteOnly};
 use kernel::common::StaticRef;
 use kernel::hil::ble_advertising;
@@ -533,6 +534,7 @@ pub struct Radio {
     tx_power: Cell<TxPower>,
     rx_client: OptionalCell<&'static dyn ble_advertising::RxClient>,
     tx_client: OptionalCell<&'static dyn ble_advertising::TxClient>,
+    buffer: TakeCell<'static, [u8]>,
 }
 
 pub static mut RADIO: Radio = Radio::new();
@@ -544,6 +546,7 @@ impl Radio {
             tx_power: Cell::new(TxPower::ZerodBm),
             rx_client: OptionalCell::empty(),
             tx_client: OptionalCell::empty(),
+            buffer: TakeCell::empty(),
         }
     }
 
@@ -631,7 +634,8 @@ impl Radio {
                 | nrf5x::constants::RADIO_STATE_TXDISABLE
                 | nrf5x::constants::RADIO_STATE_TX => {
                     self.radio_off();
-                    self.tx_client.map(|client| client.transmit_event(result));
+                    self.tx_client
+                        .map(|client| client.transmit_event(self.buffer.take().unwrap(), result));
                 }
                 nrf5x::constants::RADIO_STATE_RXRU
                 | nrf5x::constants::RADIO_STATE_RXIDLE
@@ -795,17 +799,12 @@ impl Radio {
 }
 
 impl ble_advertising::BleAdvertisementDriver for Radio {
-    fn transmit_advertisement(
-        &self,
-        buf: &'static mut [u8],
-        _len: usize,
-        channel: RadioChannel,
-    ) -> &'static mut [u8] {
+    fn transmit_advertisement(&self, buf: &'static mut [u8], _len: usize, channel: RadioChannel) {
         let res = self.replace_radio_buffer(buf);
+        self.buffer.replace(res);
         self.ble_initialize(channel);
         self.tx();
         self.enable_interrupts();
-        res
     }
 
     fn receive_advertisement(&self, channel: RadioChannel) {

kernel/src/hil/ble_advertising.rs

@@ -50,12 +50,7 @@
 use crate::returncode::ReturnCode;
 
 pub trait BleAdvertisementDriver {
-    fn transmit_advertisement(
-        &self,
-        buf: &'static mut [u8],
-        len: usize,
-        channel: RadioChannel,
-    ) -> &'static mut [u8];
+    fn transmit_advertisement(&self, buf: &'static mut [u8], len: usize, channel: RadioChannel);
     fn receive_advertisement(&self, channel: RadioChannel);
     fn set_receive_client(&self, client: &'static dyn RxClient);
     fn set_transmit_client(&self, client: &'static dyn TxClient);
@@ -70,7 +65,7 @@ pub trait RxClient {
 }
 
 pub trait TxClient {
-    fn transmit_event(&self, result: ReturnCode);
+    fn transmit_event(&self, buf: &'static mut [u8], result: ReturnCode);
 }
 
 // Bluetooth Core Specification:Vol. 6. Part B, section 1.4.1 Advertising and Data Channel Indices