[rust] a few intertwined rust build details

-Separate the two pl011 drivers so they do not need to be aware of each
other:
  - make sure the platform selects the right one
  - have the rust one make a copy of the header for C code to interact
    with
- Make the top level rust modules (app/rust_hello, rust/dev-pl011) use
  the LK module.mk which can now deal with empty modules. This cleans up
  the deps a little bit and uses existing machinery to add include
  paths.
- Move the logic to select rust modules into the qemu-virt-arm64 project
  and have it conditionally include a new virtual project file that
  encapsulates rust deps. Will need to refacto this a bit later as more
  platform/projects make use of rust, but at least moves it up to the
  project level instead of down in a single platform.

Author: travisg

app/rust_hello/rules.mk

@@ -5,6 +5,6 @@ $(info "Adding rust crate $(LOCAL_DIR)")
 
 MODULE := $(LOCAL_DIR)
 
-MODULES += $(MODULE)
+MODULE_DEPS := lib/rust_support
 
-MODULE :=
+include make/module.mk

dev/uart/pl011/include/dev/uart/pl011.h

@@ -7,7 +7,6 @@
  */
 #pragma once
 
-#include <dev/uart.h>
 #include <stdint.h>
 
 // Set this flag if the UART is a debug UART, which routes input

dev/uart/pl011/uart.c

@@ -7,9 +7,6 @@
  */
 #include "dev/uart/pl011.h"
 
-/* If rust is in use, use the Rust implementation of this driver. */
-#if !HAVE_RUST
-
 #include <assert.h>
 #include <dev/uart.h>
 #include <kernel/thread.h>
@@ -230,5 +227,3 @@ void uart_flush_rx(int port) {
 // TODO collapse this into the early/regular init routines
 void uart_init_port(int port, uint baud) {
 }
-
-#endif /* not HAVE_RUST */

platform/qemu-virt-arm/platform.c

@@ -15,7 +15,6 @@
 #include <dev/interrupt/arm_gic.h>
 #include <dev/power/psci.h>
 #include <dev/timer/arm_generic.h>
-#include <dev/uart/pl011.h>
 #include <dev/virtio.h>
 #include <dev/virtio/net.h>
 #include <lib/fdtwalk.h>
@@ -29,6 +28,12 @@
 #if WITH_LIB_MINIP
 #include <lib/minip.h>
 #endif
+#if WITH_DEV_UART_PL011
+#include <dev/uart/pl011.h>
+#endif
+#if WITH_RUST_DEV_PL011
+#include <rust/dev-pl011.h>
+#endif
 
 #define LOCAL_TRACE 0
 

platform/qemu-virt-arm/rules.mk

@@ -30,7 +30,6 @@ MODULE_DEPS += \
     dev/interrupt/arm_gic \
     dev/power/psci \
     dev/timer/arm_generic \
-    dev/uart/pl011 \
     dev/virtio/9p \
     dev/virtio/block \
     dev/virtio/gpu \
@@ -39,11 +38,11 @@ MODULE_DEPS += \
     lib/fdtwalk \
     lib/fs/9p \
 
-USE_RUST ?= 0
-
-ifeq ($(USE_RUST),1)
+ifeq ($(call TOBOOL,$(USE_RUST)),true)
 MODULE_DEPS += lib/rust_support
 MODULE_DEPS += rust/dev-pl011
+else
+MODULE_DEPS += dev/uart/pl011
 endif
 
 GLOBAL_DEFINES += \

project/qemu-virt-arm64-test.mk

@@ -1,10 +1,16 @@
 # main project for qemu-aarch64
 MODULES += \
 	app/shell \
-	app/rust_hello \
-    lib/uefi \
+    lib/uefi
 
 include project/virtual/test.mk
 include project/virtual/fs.mk
 include project/virtual/minip.mk
 include project/target/qemu-virt-arm64.mk
+
+USE_RUST ?= 0
+
+ifeq ($(call TOBOOL,$(USE_RUST)),true)
+$(info "Including rust support")
+include project/virtual/rust.mk
+endif

project/virtual/rust.mk

@@ -0,0 +1,5 @@
+# modules related to building rust support
+
+MODULES += lib/rust_support
+
+USE_RUST := 1

rust/dev-pl011/include/rust/dev-pl011.h

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2024 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#pragma once
+
+#include <stdint.h>
+
+// Set this flag if the UART is a debug UART, which routes input
+// directly into the console buffer if present.
+#define PL011_FLAG_DEBUG_UART (1u << 0)
+
+struct pl011_config {
+    uintptr_t base;
+    uint32_t irq;
+    uint32_t flag;
+};
+
+// pl011 specific initialization routines called from platform code.
+// The driver will otherwise implement the uart_* interface.
+void pl011_init_early(int port, const struct pl011_config *config);
+void pl011_init(int port);

rust/dev-pl011/rules.mk

@@ -1,3 +1,10 @@
 LOCAL_DIR := $(GET_LOCAL_DIR)
+MODULE := $(LOCAL_DIR)
+
 RUST_CRATES += $(LOCAL_DIR)
-MODULES += $(LOCAL_DIR)
+
+# add any dependencies needed for rust support
+MODULE_DEPS += lib/rust_support
+
+# make sure the local include directory is in the global include path
+include make/module.mk