Refine _bleio

This PR refines the _bleio API. It was originally motivated by
the addition of a new CircuitPython service that enables reading
and modifying files on the device. Moving the BLE lifecycle outside
of the VM motivated a number of changes to remove heap allocations
in some APIs.

It also motivated unifying connection initiation to the Adapter class
rather than the Central and Peripheral classes which have been removed.
Adapter now handles the GAP portion of BLE including advertising, which
has moved but is largely unchanged, and scanning, which has been enhanced
to return an iterator of filtered results.

Once a connection is created (either by us (aka Central) or a remote
device (aka Peripheral)) it is represented by a new Connection class.
This class knows the current connection state and can discover and
instantiate remote Services along with their Characteristics and
Descriptors.

Relates to #586

Author: tannewt

lib/utils/interrupt_char.c

@@ -49,7 +49,7 @@ void mp_keyboard_interrupt(void) {
 
 // Check to see if we've been CTRL-C'ed by autoreload or the user.
 bool mp_hal_is_interrupted(void) {
-    return MP_STATE_VM(mp_pending_exception) == MP_OBJ_FROM_PTR(&MP_STATE_VM(mp_kbd_exception));
+    return MP_STATE_VM(mp_pending_exception) != NULL;
 }
 
 #endif

main.c

@@ -69,6 +69,11 @@
 #include "shared-module/board/__init__.h"
 #endif
 
+#if CIRCUITPY_BLEIO
+#include "shared-bindings/_bleio/__init__.h"
+#include "supervisor/shared/bluetooth.h"
+#endif
+
 void do_str(const char *src, mp_parse_input_kind_t input_kind) {
     mp_lexer_t *lex = mp_lexer_new_from_str_len(MP_QSTR__lt_stdin_gt_, src, strlen(src), 0);
     if (lex == NULL) {
@@ -439,6 +444,10 @@ int __attribute__((used)) main(void) {
     // Start serial and HID after giving boot.py a chance to tweak behavior.
     serial_init();
 
+    #if CIRCUITPY_BLEIO
+    supervisor_start_bluetooth();
+    #endif
+
     // Boot script is finished, so now go into REPL/main mode.
     int exit_code = PYEXEC_FORCED_EXIT;
     bool skip_repl = true;
@@ -475,6 +484,10 @@ void gc_collect(void) {
     displayio_gc_collect();
     #endif
 
+    #if CIRCUITPY_BLEIO
+    common_hal_bleio_gc_collect();
+    #endif
+
     // This naively collects all object references from an approximate stack
     // range.
     gc_collect_root((void**)sp, ((uint32_t)port_stack_get_top() - sp) / sizeof(uint32_t));

ports/nrf/background.c

@@ -41,6 +41,10 @@
 #include "common-hal/audiopwmio/PWMAudioOut.h"
 #endif
 
+#if CIRCUITPY_BLEIO
+#include "supervisor/shared/bluetooth.h"
+#endif
+
 static bool running_background_tasks = false;
 
 void background_tasks_reset(void) {
@@ -62,6 +66,9 @@ void run_background_tasks(void) {
     i2s_background();
 #endif
 
+#if CIRCUITPY_BLEIO
+    supervisor_bluetooth_background();
+#endif
 
     #if CIRCUITPY_DISPLAYIO
     displayio_background();

ports/nrf/bluetooth/ble_drv.c

@@ -38,6 +38,8 @@
 #include "py/misc.h"
 #include "py/mpstate.h"
 
+#include "supervisor/shared/bluetooth.h"
+
 nrf_nvic_state_t nrf_nvic_state = { 0 };
 
 // Flag indicating progress of internal flash operation.
@@ -52,6 +54,14 @@ void ble_drv_reset() {
     sd_flash_operation_status = SD_FLASH_OPERATION_DONE;
 }
 
+void ble_drv_add_event_handler_entry(ble_drv_evt_handler_entry_t* entry, ble_drv_evt_handler_t func, void *param) {
+    entry->next = MP_STATE_VM(ble_drv_evt_handler_entries);
+    entry->param = param;
+    entry->func = func;
+
+    MP_STATE_VM(ble_drv_evt_handler_entries) = entry;
+}
+
 void ble_drv_add_event_handler(ble_drv_evt_handler_t func, void *param) {
     ble_drv_evt_handler_entry_t *it = MP_STATE_VM(ble_drv_evt_handler_entries);
     while (it != NULL) {
@@ -64,11 +74,7 @@ void ble_drv_add_event_handler(ble_drv_evt_handler_t func, void *param) {
 
     // Add a new handler to the front of the list
     ble_drv_evt_handler_entry_t *handler = m_new_ll(ble_drv_evt_handler_entry_t, 1);
-    handler->next = MP_STATE_VM(ble_drv_evt_handler_entries);
-    handler->param = param;
-    handler->func = func;
-
-    MP_STATE_VM(ble_drv_evt_handler_entries) = handler;
+    ble_drv_add_event_handler_entry(handler, func, param);
 }
 
 void ble_drv_remove_event_handler(ble_drv_evt_handler_t func, void *param) {
@@ -127,10 +133,20 @@ void SD_EVT_IRQHandler(void) {
             break;
         }
 
+        ble_evt_t* event = (ble_evt_t *)m_ble_evt_buf;
+
+        if (supervisor_bluetooth_hook(event)) {
+            continue;
+        }
+
         ble_drv_evt_handler_entry_t *it = MP_STATE_VM(ble_drv_evt_handler_entries);
+        bool done = false;
         while (it != NULL) {
-            it->func((ble_evt_t *)m_ble_evt_buf, it->param);
+            done = it->func(event, it->param) || done;
             it = it->next;
         }
+        if (!done) {
+            //mp_printf(&mp_plat_print, "Unhandled ble event: 0x%04x\n", event->header.evt_id);
+        }
     }
 }

ports/nrf/bluetooth/ble_drv.h

@@ -29,6 +29,8 @@
 #ifndef MICROPY_INCLUDED_NRF_BLUETOOTH_BLE_DRV_H
 #define MICROPY_INCLUDED_NRF_BLUETOOTH_BLE_DRV_H
 
+#include <stdbool.h>
+
 #include "ble.h"
 
 #define MAX_TX_IN_PROGRESS 10
@@ -48,7 +50,7 @@
 #define UNIT_1_25_MS  (1250)
 #define UNIT_10_MS    (10000)
 
-typedef void (*ble_drv_evt_handler_t)(ble_evt_t*, void*);
+typedef bool (*ble_drv_evt_handler_t)(ble_evt_t*, void*);
 
 typedef enum {
     SD_FLASH_OPERATION_DONE,
@@ -69,4 +71,7 @@ void ble_drv_reset(void);
 void ble_drv_add_event_handler(ble_drv_evt_handler_t func, void *param);
 void ble_drv_remove_event_handler(ble_drv_evt_handler_t func, void *param);
 
+// Allow for user provided entries to prevent allocations outside the VM.
+void ble_drv_add_event_handler_entry(ble_drv_evt_handler_entry_t* entry, ble_drv_evt_handler_t func, void *param);
+
 #endif // MICROPY_INCLUDED_NRF_BLUETOOTH_BLE_DRV_H

ports/nrf/boards/adafruit_nrf52840_s140_v6.ld

@@ -16,6 +16,7 @@
     0x00000000..0x00000FFF   (4KB) Master Boot Record
 */
 
+
 /* Specify the memory areas (S140 6.x.x) */
 MEMORY
 {
@@ -26,7 +27,10 @@ MEMORY
     FLASH_FATFS (r) : ORIGIN = 0x000AD000, LENGTH = 0x040000
 
     /* 0x2000000 - RAM:ORIGIN is reserved for Softdevice */
-    RAM (xrw)       : ORIGIN = 0x20004000, LENGTH = 0x20040000 - 0x20004000
+    /* SoftDevice 6.1.0 takes 0x1628 bytes (5.54 kb) minimum. */
+    /* To measure the minimum required amount of memory for given configuration, set this number
+       high enough to work and then check the mutation of the value done by sd_ble_enable. */
+    RAM (xrw)       : ORIGIN = 0x20000000 + 16K, LENGTH = 256K - 16K
 }
 
 /* produce a link error if there is not this amount of RAM for these sections */
@@ -38,7 +42,8 @@ _minimum_heap_size = 0;
 /*_stack_end = ORIGIN(RAM) + LENGTH(RAM);*/
 _estack = ORIGIN(RAM) + LENGTH(RAM);
 
-/* RAM extents for the garbage collector */
+/* RAM extents for the garbage collector and soft device init */
+_ram_start = ORIGIN(RAM);
 _ram_end = ORIGIN(RAM) + LENGTH(RAM);
 _heap_end = 0x20020000; /* tunable */