extmod/modopenamp: Implement streaming protocol for endpoints.

iabdalkader · iabdalkader · commit 858259f9a177 · 2024-03-24T16:15:27.000+01:00
This patch implements Endpoint's streaming protocol, allowing endpoints
to be used with select/poll or asyncio. It also implements an
`endpoint.recv()` function, whose behavior matches that of UDP sockets'
recv(). Calling `endpoint.recv()` returns a single message, truncated
to fit the requested number of bytes. If two messages are pending on
the endpoint, the code must do two separate reads to get them both.
The queuing of RPMsg messages is done by holding RPMsg buffers and
releasing them when they are no longer needed (i.e., when `recv` is
called on all of them). This avoids the double copying of buffers,
saves memory, but also allows the host to block the remote if it's not
receiving messages (if the queue size is the same as the number of
buffers in the VRING). Note that the queuing of RPMsg messages is only
enabled if `callback=None` (i.e., when the application is not
processing messages synchronously).

Signed-off-by: iabdalkader &lt;i.abdalkader@gmail.com&gt;
diff --git a/extmod/modopenamp.c b/extmod/modopenamp.c
@@ -32,6 +32,8 @@
 #include "py/obj.h"
 #include "py/nlr.h"
 #include "py/runtime.h"
+#include "py/stream.h"
+#include "py/mperrno.h"
 #include "py/mpprint.h"
 
 #include "metal/sys.h"
@@ -44,6 +46,7 @@
 #include "openamp/open_amp.h"
 #include "openamp/remoteproc.h"
 #include "openamp/remoteproc_loader.h"
+#include "lib/rpmsg/rpmsg_internal.h"
 #include "modopenamp.h"
 
 #if !MICROPY_ENABLE_FINALISER
@@ -128,19 +131,52 @@ static MP_DEFINE_CONST_OBJ_TYPE(
     );
 
 // ###################### RPMsg Endpoint class ######################
+// The number of RPMsg buffers to hold for an Endpoint. Note if this number matches
+// the number of buffers per VRING, a full ring buffer/queue will cause the other
+// side to block, because all buffers will be held by the application. If it's less
+// than the number of buffers in a VRING, messages will be dropped if this side is not
+// receiving messages.
+#define ENDPOINT_RPMSG_RING_SIZE VRING_NUM_BUFFS
 typedef struct _endpoint_obj_t {
     mp_obj_base_t base;
     mp_obj_t name;
     mp_obj_t callback;
     struct rpmsg_endpoint ep;
+    volatile uint32_t head;
+    volatile uint32_t tail;
+    void *rpmsg_buf[ENDPOINT_RPMSG_RING_SIZE];
 } endpoint_obj_t;
 
 static const mp_obj_type_t endpoint_type;
 
+static int endpoint_rpmsg_enqueue(endpoint_obj_t *ept, void *buf) {
+    if (((ept->tail + 1) % ENDPOINT_RPMSG_RING_SIZE) != ept->head) {
+        ept->rpmsg_buf[ept->tail] = buf;
+        ept->tail = (ept->tail + 1) % ENDPOINT_RPMSG_RING_SIZE;
+        rpmsg_hold_rx_buffer(&ept->ep, buf);
+        return 0;
+    }
+    return -1;
+}
+
+static size_t endpoint_rpmsg_dequeue(endpoint_obj_t *ept, void *buf, size_t len) {
+    size_t size = 0;
+    if (ept->head != ept->tail) {
+        void *rpmsg = ept->rpmsg_buf[ept->head];
+        size = MIN(RPMSG_LOCATE_HDR(rpmsg)->len, len);
+        memcpy(buf, rpmsg, size);
+        ept->head = (ept->head + 1) % ENDPOINT_RPMSG_RING_SIZE;
+        rpmsg_release_rx_buffer(&ept->ep, rpmsg);
+    }
+    return size;
+}
+
 static int endpoint_recv_callback(struct rpmsg_endpoint *ept, void *data, size_t len, uint32_t src, void *priv) {
     debug_printf("endpoint_recv_callback() message received src: %lu msg len: %d\n", src, len);
     endpoint_obj_t *self = metal_container_of(ept, endpoint_obj_t, ep);
-    if (self->callback != mp_const_none) {
+    if (self->callback == mp_const_none) {
+        endpoint_rpmsg_enqueue(self, data);
+    } else {
         mp_call_function_2(self->callback, mp_obj_new_int(src), mp_obj_new_bytearray_by_ref(len, data));
     }
     return 0;
@@ -195,6 +231,40 @@ static mp_obj_t endpoint_send(uint n_args, const mp_obj_t *pos_args, mp_map_t *k
 }
 static MP_DEFINE_CONST_FUN_OBJ_KW(endpoint_send_obj, 2, endpoint_send);
 
+static mp_obj_t endpoint_recv(uint n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_timeout };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_timeout, MP_ARG_INT | MP_ARG_KW_ONLY,  {.u_int = 0 } },
+    };
+
+    // Parse args.
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 2, pos_args + 2, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    endpoint_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
+    vstr_t vstr;
+    size_t len = mp_obj_get_int(pos_args[1]);
+    vstr_init_len(&vstr, len);
+
+    mp_int_t timeout = args[ARG_timeout].u_int;
+    for (mp_uint_t start = mp_hal_ticks_ms(); ;) {
+        vstr.len = endpoint_rpmsg_dequeue(self, vstr.buf, len);
+        if (vstr.len > 0) {
+            break;
+        }
+        if (timeout == 0) {
+            break;
+        }
+        if (timeout > 0 && (mp_hal_ticks_ms() - start > timeout)) {
+            mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("timeout waiting for message"));
+        }
+        MICROPY_EVENT_POLL_HOOK
+    }
+
+    return mp_obj_new_bytes_from_vstr(&vstr);
+}
+static MP_DEFINE_CONST_FUN_OBJ_KW(endpoint_recv_obj, 2, endpoint_recv);
+
 static mp_obj_t endpoint_is_ready(mp_obj_t self_in) {
     endpoint_obj_t *self = MP_OBJ_TO_PTR(self_in);
     return is_rpmsg_ept_ready(&self->ep) ? mp_const_true : mp_const_false;
@@ -209,12 +279,13 @@ static mp_obj_t endpoint_deinit(mp_obj_t self_in) {
 static MP_DEFINE_CONST_FUN_OBJ_1(endpoint_deinit_obj, endpoint_deinit);
 
 static mp_obj_t endpoint_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
-    enum { ARG_name, ARG_callback, ARG_src, ARG_dest };
+    enum { ARG_name, ARG_callback, ARG_src, ARG_dest, ARG_buf };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_name, MP_ARG_OBJ | MP_ARG_REQUIRED,  {.u_rom_obj = MP_ROM_NONE } },
-        { MP_QSTR_callback, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE } },
-        { MP_QSTR_src, MP_ARG_INT | MP_ARG_KW_ONLY,  {.u_int = RPMSG_ADDR_ANY } },
-        { MP_QSTR_dest, MP_ARG_INT | MP_ARG_KW_ONLY,  {.u_int = RPMSG_ADDR_ANY } },
+        { MP_QSTR_name, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE } },
+        { MP_QSTR_callback, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE } },
+        { MP_QSTR_src, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = RPMSG_ADDR_ANY } },
+        { MP_QSTR_dest, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = RPMSG_ADDR_ANY } },
+        { MP_QSTR_buf, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 2048 } },
     };
 
     // Parse args.
@@ -224,6 +295,7 @@ static mp_obj_t endpoint_make_new(const mp_obj_type_t *type, size_t n_args, size
     endpoint_obj_t *self = mp_obj_malloc_with_finaliser(endpoint_obj_t, &endpoint_type);
     self->name = args[ARG_name].u_obj;
     self->callback = args[ARG_callback].u_obj;
+    self->head = self->tail = 0;
 
     if (MP_STATE_PORT(virtio_device) == NULL) {
         openamp_init();
@@ -241,15 +313,66 @@ static const mp_rom_map_elem_t endpoint_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_Endpoint) },
     { MP_ROM_QSTR(MP_QSTR___del__), MP_ROM_PTR(&endpoint_deinit_obj) },
     { MP_ROM_QSTR(MP_QSTR_send), MP_ROM_PTR(&endpoint_send_obj) },
+    { MP_ROM_QSTR(MP_QSTR_recv), MP_ROM_PTR(&endpoint_recv_obj) },
     { MP_ROM_QSTR(MP_QSTR_is_ready), MP_ROM_PTR(&endpoint_is_ready_obj) },
 };
 static MP_DEFINE_CONST_DICT(endpoint_locals_dict, endpoint_locals_dict_table);
 
+mp_uint_t endpoint_read(mp_obj_t self_in, void *buf, mp_uint_t size, int *errcode) {
+    endpoint_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    if (!is_rpmsg_ept_ready(&self->ep)) {
+        return MP_STREAM_ERROR;
+    }
+    return endpoint_rpmsg_dequeue(self, buf, size);
+}
+
+mp_uint_t endpoint_write(mp_obj_t self_in, const void *buf, mp_uint_t size, int *errcode) {
+    endpoint_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    int ret = 0;
+    if (!is_rpmsg_ept_ready(&self->ep)) {
+        ret = MP_STREAM_ERROR;
+    } else {
+        ret = rpmsg_send(&self->ep, buf, size);
+        if (ret < 0) {
+            ret = MP_STREAM_ERROR;
+        }
+    }
+    return ret;
+}
+
+mp_uint_t endpoint_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    endpoint_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_uint_t ret = 0;
+    if (request == MP_STREAM_CLOSE) {
+        rpmsg_destroy_ept(&self->ep);
+    } else if (request == MP_STREAM_POLL) {
+        if ((arg & MP_STREAM_POLL_RD) && self->head != self->tail) {
+            ret |= MP_STREAM_POLL_RD;
+        }
+
+        if ((arg & MP_STREAM_POLL_WR) && is_rpmsg_ept_ready(&self->ep)) {
+            ret |= MP_STREAM_POLL_WR;
+        }
+    } else {
+        *errcode = MP_EINVAL;
+        ret = MP_STREAM_ERROR;
+    }
+    return ret;
+}
+
+static const mp_stream_p_t endpoint_stream_p = {
+    .read = endpoint_read,
+    .write = endpoint_write,
+    .ioctl = endpoint_ioctl,
+    .is_text = false,
+};
+
 static MP_DEFINE_CONST_OBJ_TYPE(
     endpoint_type,
     MP_QSTR_Endpoint,
     MP_TYPE_FLAG_NONE,
     make_new, endpoint_make_new,
+    protocol, &endpoint_stream_p,
     locals_dict, &endpoint_locals_dict
     );
 
