wip host_alarmclock

15 files changed, 436 insertions, 199 deletions

diff --git a/libhw/CMakeLists.txt b/libhw/CMakeLists.txt
index 0dee422..1baeee8 100644
--- a/libhw/CMakeLists.txt
+++ b/libhw/CMakeLists.txt
@@ -27,7 +27,8 @@ endif()
 if (PICO_PLATFORM STREQUAL "host")
 	target_include_directories(libhw SYSTEM INTERFACE ${CMAKE_CURRENT_SOURCE_DIR}/host_include)
 	target_sources(libhw INTERFACE
-		host_bootclock.c
+		host_sigrt.c
+		host_alarmclock.c
 		host_net.c
 	)
 endif()
diff --git a/libhw/alarmclock.c b/libhw/alarmclock.c
new file mode 100644
index 0000000..7b311c0
--- /dev/null
+++ b/libhw/alarmclock.c
@@ -0,0 +1,21 @@
+/* libhw/alarmclock.c - Device-independent <libhw/generic/alarmclock.h> utilities
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <libcr/coroutine.h>
+#include <libmisc/vcall.h>
+
+#include <libhw/generic/alarmclock.h>
+
+static void alarmclock_sleep_intrhandler(void *_arg) {
+	cid_t *cid = _arg;
+	cr_unpause_from_intrhandler(*cid);
+}
+
+void alarmclock_sleep_until_ns(implements_alarmclock *clock, uint64_t abstime_ns) {
+	cid_t cid = cr_getcid();
+	struct alarmclock_trigger trigger;
+	VCALL(clock, add_trigger, &trigger, abstime_ns, alarmclock_sleep_intrhandler, &cid);
+}
diff --git a/libhw/common_include/libhw/generic/alarmclock.h b/libhw/common_include/libhw/generic/alarmclock.h
new file mode 100644
index 0000000..bf0d42f
--- /dev/null
+++ b/libhw/common_include/libhw/generic/alarmclock.h
@@ -0,0 +1,98 @@
+/* libhw/generic/alarmclock.h - Device-independent alarmclock definitions
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _LIBHW_GENERIC_ALARMCLOCK_H_
+#define _LIBHW_GENERIC_ALARMCLOCK_H_
+
+#include <stdbool.h> /* for bool */
+#include <stdint.h>  /* for uint{n}_t and UINT{n}_C */
+
+#include <libmisc/private.h>
+#include <libmisc/vcall.h>
+
+/* Useful constants ***********************************************************/
+
+#define NS_PER_S UINT64_C(1000000000) /* needs at least log₂(10⁹) ≈ 29.9 bits */
+#define US_PER_S UINT64_C(1000000)    /* needs at least log₂(10⁶) ≈ 19.9 bits */
+#define MS_PER_S UINT64_C(1000)       /* needs at least log₂(10³) ≈  9.9 bits */
+
+/* Structs ********************************************************************/
+
+struct alarmclock_trigger;
+struct alarmclock_trigger {
+	BEGIN_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
+	void                            *alarmclock;
+	struct alarmclock_trigger       *prev, *next;
+
+	uint64_t                         fire_at_ns;
+	void                             (*cb)(void *);
+	void                            *cb_arg;
+	END_PRIVATE(LIBHW_GENERIC_ALARMCLOCK_H)
+};
+
+/* Interface ******************************************************************/
+
+struct alarmclock_vtable;
+
+typedef struct {
+	struct alarmclock_vtable     *vtable;
+} implements_alarmclock;
+
+struct alarmclock_vtable {
+	/**
+	 * (2⁶⁴-1 nanoseconds is more than 500 years; there is little
+	 * risk of this overflowing)
+	 */
+	uint64_t (*get_time_ns)(implements_alarmclock *self);
+
+	/**
+	 * Returns true on error.
+	 *
+	 * Implementations may return an error if fire_at_ns is more
+	 * than UINT32_MAX µs (72 minutes) in the future.
+	 *
+	 * If fire_at_ns is in the past, then it will fire
+	 * immediately.
+	 */
+	bool     (*add_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger,
+	                        uint64_t   fire_at_ns,
+	                        void       (*cb)(void *),
+	                        void      *cb_arg);
+
+	void     (*del_trigger)(implements_alarmclock *self, struct alarmclock_trigger *trigger);
+};
+
+/* Utilities ******************************************************************/
+
+void alarmclock_sleep_until_ns(implements_alarmclock *clock, uint64_t abstime_ns);
+
+static inline void alarmclock_sleep_for_ns(implements_alarmclock *clock, uint64_t delta_ns) {
+	alarmclock_sleep_until_ns(clock, VCALL(clock, get_time_ns) + delta_ns);
+}
+
+static inline void alarmclock_sleep_for_us(implements_alarmclock *clock, uint64_t delta_us) {
+	alarmclock_sleep_for_ns(clock, delta_us * (NS_PER_S/US_PER_S));
+}
+
+static inline void alarmclock_sleep_for_ms(implements_alarmclock *clock, uint64_t delta_ms) {
+	alarmclock_sleep_for_ns(clock, delta_ms * (NS_PER_S/MS_PER_S));
+}
+
+static inline void alarmclock_sleep_for_s(implements_alarmclock *clock, uint64_t delta_s) {
+	alarmclock_sleep_for_ns(clock, delta_s * NS_PER_S);
+}
+
+/* Globals ********************************************************************/
+
+extern const implements_alarmclock *bootclock;
+
+#define sleep_until_ns(t) alarmclock_sleep_until_ns(bootclock, t)
+#define sleep_for_ns(t)   alarmclock_sleep_for_ns(bootclock, t)
+#define sleep_for_us(t)   alarmclock_sleep_for_us(bootclock, t)
+#define sleep_for_ms(t)   alarmclock_sleep_for_ms(bootclock, t)
+#define sleep_for_s(t)    alarmclock_sleep_for_s(bootclock, t)
+
+#endif /* _LIBHW_GENERIC_ALARMCLOCK_H_ */
diff --git a/libhw/common_include/libhw/generic/bootclock.h b/libhw/common_include/libhw/generic/bootclock.h
deleted file mode 100644
index bea5338..0000000
--- a/libhw/common_include/libhw/generic/bootclock.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/* libhw/generic/bootclock.h - Device-independent clock definitions
- *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
- * SPDX-License-Identifier: AGPL-3.0-or-later
- */
-
-#ifndef _LIBHW_GENERIC_BOOTCLOCK_H_
-#define _LIBHW_GENERIC_BOOTCLOCK_H_
-
-#include <stdint.h> /* for uint{n}_t and UINT{n}_C */
-
-#define NS_PER_S UINT64_C(1000000000) /* needs at least log₂(10⁹) ≈ 29.9 bits */
-#define US_PER_S UINT64_C(1000000)    /* needs at least log₂(10⁶) ≈ 19.9 bits */
-#define MS_PER_S UINT64_C(1000)       /* needs at least log₂(10³) ≈  9.9 bits */
-
-/**
- * (2⁶⁴-1 nanoseconds is more than 500 years; there is little
- * risk of this overflowing)
- */
-uint64_t bootclock_get_ns(void);
-
-#endif /* _LIBHW_GENERIC_BOOTCLOCK_H_ */
diff --git a/libhw/common_include/libhw/generic/net.h b/libhw/common_include/libhw/generic/net.h
index af8844f..08b411f 100644
--- a/libhw/common_include/libhw/generic/net.h
+++ b/libhw/common_include/libhw/generic/net.h
@@ -34,7 +34,7 @@ struct net_eth_addr {
 /* Streams (e.g. TCP) *********************************************************/
 
 struct net_stream_listener_vtable;
-struct net_stream_conn_btable;
+struct net_stream_conn_vtable;
 
 typedef struct {
 	struct net_stream_listener_vtable       *vtable;
diff --git a/libhw/host_alarmclock.c b/libhw/host_alarmclock.c
new file mode 100644
index 0000000..a89294c
--- /dev/null
+++ b/libhw/host_alarmclock.c
@@ -0,0 +1,87 @@
+/* libhw/host_alarmclock.c - <libhw/generic/alarmclock.h> implementation for POSIX hosts
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <assert.h>
+#include <time.h> /* for clock_gettime(), CLOCK_MONOTONIC, clockid_t, struct timespec */
+
+#include <libmisc/vcall.h>
+
+#define IMPLEMENTATION_FOR_LIBHW_GENERIC_ALARMCLOCK_H YES
+#include <libhw/generic/alarmclock.h>
+
+#include "host_sigrt.h"
+
+struct hostclock {
+	implements_alarmclock;
+	bool                             initialized;
+	clockid_t                        clock_id;
+	timer_t                          timer_id;
+	struct alarmclock_trigger       *queue;
+};
+
+static uint64_t hostclock_get_ns(implements_alarmclock *_alarmclock) {
+	struct hostclock *alarmclock =
+		VCALL_SELF(struct hostclock, implements_alarmclock, _alarmclock);
+	assert(alarmclock);
+
+	struct timespec ts;
+	int r;
+
+	r = clock_gettime(alarmclock->clock_id, &ts);
+	assert(r == 0);
+
+	return (((uint64_t)ts.tv_sec) * NS_PER_S) + (uint64_t)ts.tv_nsec;
+}
+
+static void hostclock_handle_sig_alarm(int UNUSED(sig), siginfo_t *info, void *UNUSED(ucontext)) {
+	struct hostclock *alarmclock = info->si_value.sival_ptr;
+	assert(alarmclock)
+
+	while (alarmclock->queue &&
+	       alarmclock->queue->fire_at_ns <= hostclock_get_ns(alarmclock)) {
+		struct alarmclock_trigger *trigger = alarmclock->queue;
+		trigger->cb(trigger->cb_arg);
+		alarmclock->queue = trigger->next;
+		trigger->alarmclock = NULL;
+		trigger->next = NULL;
+		trigger->prev = NULL;
+	}
+
+	if (alarmclock->queue) {
+		timer_settime(alarmclock
+	}
+		timer_hw->alarm[alarm_num] = (uint32_t)NS_TO_US_ROUNDUP(alarmclock->queue->fire_at_ns);
+}
+
+static bool hostclock_add_trigger(implements_alarmclock *self,
+                                      struct alarmclock_trigger *trigger,
+                                      uint64_t   fire_at_ns,
+                                      void       (*cb)(void *),
+                                      void      *cb_arg) {
+	struct hostclock *clock =
+		VCALL_SELF(struct hostclock, implements_alarmclock, _clock);
+
+
+}
+
+static void hostclock_del_trigger(implements_alarmclock *self,
+                                      struct alarmclock_trigger *trigger) {
+}
+
+/* Globals ********************************************************************/
+
+static struct alarmclock_vtable hostclock_vtable = {
+	.get_time_ns = hostclock_get_time_ns,
+	.add_trigger = hostclock_add_trigger,
+	.del_trigger = hostclock_del_trigger,
+};
+
+static struct hostclock clock_monotonic = {
+	.vtable  = hostclock_vtable,
+	.clockid = CLOCK_MONOTONIC,
+};
+
+const implements_alarmclock *bootclock = &clock_monotonic;
diff --git a/libhw/host_bootclock.c b/libhw/host_bootclock.c
deleted file mode 100644
index ca9565c..0000000
--- a/libhw/host_bootclock.c
+++ /dev/null
@@ -1,20 +0,0 @@
-/* libhw/host_bootclock.c - <libhw/generic/bootclock.h> implementation for POSIX hosts
- *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
- * SPDX-License-Identifier: AGPL-3.0-or-later
- */
-
-#include <assert.h>
-#include <time.h> /* for clock_gettime(), CLOCK_MONOTONIC, struct timespec */
-
-#include <libhw/generic/bootclock.h>
-
-uint64_t bootclock_get_ns(void) {
-	struct timespec ts;
-	int r;
-
-	r = clock_gettime(CLOCK_MONOTONIC, &ts);
-	assert(r == 0);
-
-	return (((uint64_t)ts.tv_sec) * NS_PER_S) + (uint64_t)ts.tv_nsec;
-}
diff --git a/libhw/host_net.c b/libhw/host_net.c
index 904019a..97e7726 100644
--- a/libhw/host_net.c
+++ b/libhw/host_net.c
@@ -17,16 +17,18 @@
 #include <sys/socket.h> /* for struct sockaddr{,_storage}, SOCK_*, SOL_*, SO_*, socket(), setsockopt(), bind(), listen(), accept() */
 /* async */
 #include <pthread.h>    /* for pthread_* */
-#include <signal.h>     /* for siginfo_t, struct sigaction, enum sigval, sigaction(), SIGRTMIN, SIGRTMAX, SA_SIGINFO */
+#include <signal.h>     /* for siginfo_t, struct sigaction, enum sigval, sigaction(), SA_SIGINFO */
 
 #include <libcr/coroutine.h>
 #include <libmisc/vcall.h>
 
-#include <libhw/generic/bootclock.h>
+#include <libhw/generic/alarmclock.h>
 
 #define IMPLEMENTATION_FOR_LIBHW_HOST_NET_H YES
 #include <libhw/host_net.h>
 
+#include "host_sigrt.h" /* for host_sigrt_alloc(), ns_to_host_us_time() */
+
 /* common *********************************************************************/
 
 #define UNUSED(name) /* name __attribute__ ((unused)) */
@@ -43,9 +45,7 @@ static void hostnet_init(void) {
 	if (hostnet_sig_io)
 		return;
 
-	hostnet_sig_io = SIGRTMIN;
-	if (hostnet_sig_io > SIGRTMAX)
-		error(1, 0, "SIGRTMAX exceeded");
+	hostnet_sig_io = host_sigrt_alloc();
 
 	action.sa_flags = SA_SIGINFO;
 	action.sa_sigaction = hostnet_handle_sig_io;
@@ -230,17 +230,12 @@ static ssize_t hostnet_tcp_read(implements_net_stream_conn *_conn, void *buf, si
 		.ret          = &ret,
 	};
 	if (conn->read_deadline_ns) {
-		uint64_t now_ns = bootclock_get_ns();
+		uint64_t now_ns = VCALL(bootclock, get_time_ns);
 		if (conn->read_deadline_ns < now_ns)
 			return -NET_ETIMEDOUT;
-		uint64_t timeout_ns = conn->read_deadline_ns-now_ns;
-		args.timeout.tv_sec = timeout_ns
-			/NS_PER_S;
-		args.timeout.tv_usec = (timeout_ns - ((uint64_t)args.timeout.tv_sec)*NS_PER_S)
-			/(NS_PER_S/US_PER_S);
+		args.timeout = ns_to_host_us_time(conn->read_deadline_ns-now_ns);
 	} else {
-		args.timeout.tv_sec = 0;
-		args.timeout.tv_usec = 0;
+		args.timeout = ns_to_host_us_time(0);
 	}
 
 	if (RUN_PTHREAD(hostnet_pthread_read, &args))
@@ -500,17 +495,12 @@ static ssize_t hostnet_udp_recvfrom(implements_net_packet_conn *_conn, void *buf
 		.ret_port     = ret_port,
 	};
 	if (conn->read_deadline_ns) {
-		uint64_t now_ns = bootclock_get_ns();
+		uint64_t now_ns = VCALL(bootclock, get_time_ns);
 		if (conn->read_deadline_ns < now_ns)
 			return -NET_ETIMEDOUT;
-		uint64_t timeout_ns = conn->read_deadline_ns-now_ns;
-		args.timeout.tv_sec = timeout_ns
-			/NS_PER_S;
-		args.timeout.tv_usec = (timeout_ns - ((uint64_t)args.timeout.tv_sec)*NS_PER_S)
-			/(NS_PER_S/US_PER_S);
+		args.timeout = ns_to_host_us_time(conn->read_deadline_ns-now_ns);
 	} else {
-		args.timeout.tv_sec = 0;
-		args.timeout.tv_usec = 0;
+		args.timeout = ns_to_host_us_time(0);
 	}
 
 	if (RUN_PTHREAD(hostnet_pthread_recvfrom, &args))
diff --git a/libhw/host_sigrt.c b/libhw/host_sigrt.c
new file mode 100644
index 0000000..66041fc
--- /dev/null
+++ b/libhw/host_sigrt.c
@@ -0,0 +1,21 @@
+/* libhw/host_sigrt.c - Manage glibc realtime signals
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <error.h>  /* for error(3gnu) */
+#include <signal.h> /* for SIGRTMIN, SIGRTMAX */
+
+#include "host_sigrt.h"
+
+int host_alloc_sigrt(void) {
+	static int next = 0;
+
+	if (!next)
+		next = SIGRTMIN;
+	int ret = next++;
+	if (ret > SIGRTMAX)
+		error(1, 0, "SIGRTMAX exceeded");
+	return ret;
+}
diff --git a/libhw/host_sigrt.h b/libhw/host_sigrt.h
new file mode 100644
index 0000000..fa5675b
--- /dev/null
+++ b/libhw/host_sigrt.h
@@ -0,0 +1,47 @@
+/* libhw/host_sigrt.h - Manage glibc realtime signals
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _LIBHW_HOST_SIGRT_H_
+#define _LIBHW_HOST_SIGRT_H_
+
+#include <time.h>                     /* for struct timespec */
+#include <sys/time.h>                 /* for struct timeval */
+
+#include <libhw/generic/alarmclock.h> /* for {X}S_PER_S */
+
+int host_sigrt_alloc(void);
+
+typedef struct timeval  host_us_time_t;
+typedef struct timespec host_ns_time_t;
+
+static inline host_us_time_t ns_to_host_us_time(uint64_t time_ns) {
+	host_us_time_t ret;
+	ret.tv_sec = time_ns
+		/NS_PER_S;
+	ret.tv_usec = (time_ns - ((uint64_t)ret.tv_sec)*NS_PER_S)
+		/(NS_PER_S/US_PER_S);
+	return ret;
+}
+
+static inline host_ns_time_t ns_to_host_ns_time(uint64_t time_ns) {
+	host_ns_time_t ret;
+	ret.tv_sec = time_ns
+		/NS_PER_S;
+	ret.tv_nsec = time_ns - ((uint64_t)ret.tv_sec)*NS_PER_S;
+	return ret;
+}
+
+static inline uint64_t ns_from_host_us_time(host_us_time_t host_time) {
+	return (((uint64_t)ts.tv_sec) * NS_PER_S) +
+		((uint64_t)ts.tv_nsec * (NS_PER_S/US_PER_S));
+}
+
+static inline uint64_t ns_from_host_ns_time(host_ns_time_t host_time) {
+	return (((uint64_t)ts.tv_sec) * NS_PER_S) +
+		((uint64_t)ts.tv_nsec);
+}
+
+#endif /* _LIBHW_HOST_SIGRT_H_ */
diff --git a/libhw/rp2040_hwspi.c b/libhw/rp2040_hwspi.c
index b4adeb7..4edcdf7 100644
--- a/libhw/rp2040_hwspi.c
+++ b/libhw/rp2040_hwspi.c
@@ -1,5 +1,4 @@
-/* libhw/rp2040_hwspi.c - `implements_spi` implementation for the RP2040's
- *                        ARM Primecell SSP (PL022) (implementation file)
+/* libhw/rp2040_hwspi.c - <libhw/generic/spi.h> implementation for the RP2040's ARM Primecell SSP (PL022)
  *
  * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
diff --git a/libhw/rp2040_hwtimer.c b/libhw/rp2040_hwtimer.c
index b8255b8..6daa69d 100644
--- a/libhw/rp2040_hwtimer.c
+++ b/libhw/rp2040_hwtimer.c
@@ -1,120 +1,165 @@
-/* libhw/rp2040_hwtimer.c - Manage the RP2040's hardware timer
+/* libhw/rp2040_hwtimer.c - <libhw/generic/alarmclock.h> implementation for the RP2040's hardware timer
  *
  * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
+#include <assert.h>
+
 #include <hardware/irq.h>   /* pico-sdk:hardware_irq */
 #include <hardware/timer.h> /* pico-sdk:hardware_timer */
 
 #include <libcr/coroutine.h>
+#include <libmisc/vcall.h>
+
+#define IMPLEMENTATION_FOR_LIBHW_GENERIC_ALARMCLOCK_H YES
+#include <libhw/generic/alarmclock.h>
+#include <libhw/rp2040_hwtimer.h>
+
+/* Init ***********************************************************************/
+
+struct rp2040_hwtimer {
+	implements_alarmclock;
+	enum rp2040_hwalarm_instance     alarm_num;
+	bool                             initialized;
+	struct alarmclock_trigger       *queue;
+};
+
+static uint64_t rp2040_hwtimer_get_time_ns(implements_alarmclock *self);
+static bool     rp2040_hwtimer_add_trigger(implements_alarmclock *self,
+                                           struct alarmclock_trigger *trigger,
+                                           uint64_t   fire_at_ns,
+                                           void       (*cb)(void *),
+                                           void      *cb_arg);
+static void     rp2040_hwtimer_del_trigger(implements_alarmclock *self,
+                                           struct alarmclock_trigger *trigger);
+
+static struct alarmclock_vtable rp2040_hwtimer_vtable = {
+	.get_time_ns = rp2040_hwtimer_get_time_ns,
+	.add_trigger = rp2040_hwtimer_add_trigger,
+	.del_trigger = rp2040_hwtimer_del_trigger,
+};
+
+static struct rp2040_hwtimer hwtimers[] = {
+	{ .vtable = &rp2040_hwtimer_vtable, .alarm_num = 0 },
+	{ .vtable = &rp2040_hwtimer_vtable, .alarm_num = 1 },
+	{ .vtable = &rp2040_hwtimer_vtable, .alarm_num = 2 },
+	{ .vtable = &rp2040_hwtimer_vtable, .alarm_num = 3 },
+};
+static_assert(sizeof(hwtimers)/sizeof(hwtimers[0]) == _RP2040_HWALARM_NUM);
+
+implements_alarmclock *rp2040_hwtimer(enum rp2040_hwalarm_instance alarm_num) {
+	assert(alarm_num < _RP2040_HWALARM_NUM);
+	return &hwtimers[alarm_num];
+}
 
-#define IMPLEMENTATION_FOR_LIBHW_RP2040_HWALARM_H YES
-#include <libhw/rp2040_hwalarm.h>
-#include <libhw/generic/bootclock.h>
+/* Main implementation ********************************************************/
 
-uint64_t bootclock_get_ns(void) {
-	return timer_time_us_64(timer_hw)*(NS_PER_S/US_PER_S);
+static uint64_t rp2040_hwtimer_get_time_ns(implements_alarmclock *) {
+	return timer_time_us_64(timer_hw) * (NS_PER_S/US_PER_S);
 }
 
-static struct {
-	bool                         initialized;
-	struct rp2040_hwalarm_trigger *queue;
-} alarms[_RP2040_HWALARM_NUM] = {0};
-
-static void rp2040_hwalarm_intrhandler(void) {
-    uint irq_num = __get_current_exception() - VTABLE_FIRST_IRQ;
-    uint alarm_num = TIMER_ALARM_NUM_FROM_IRQ(irq_num);
-    assert(alarm_num < _RP2040_HWALARM_NUM);
-
-    typeof(alarms[0]) *alarm = &alarms[alarm_num];
-
-    uint64_t now_us = timer_time_us_64(timer_hw);
-    while (alarm->queue && alarm->queue->fire_at_us <= now_us) {
-	    struct rp2040_hwalarm_trigger *trigger = alarm->queue;
-	    trigger->cb(trigger->cb_arg);
-	    alarm->queue = trigger->next;
-	    trigger->alarm = NULL;
-	    trigger->next = NULL;
-	    trigger->prev = NULL;
-	    now_us = timer_time_us_64(timer_hw);
-    }
-
-    hw_clear_bits(&timer_hw->intf, 1 << alarm_num);
-    if (alarm->queue)
-	    timer_hw->alarm[alarm_num] = (uint32_t)alarm->queue->fire_at_us;
-}
+#define NS_TO_US_ROUNDUP(x) ( ( (x) + (NS_PER_S/US_PER_S)-1) / (NS_PER_S/US_PER_S) )
 
-bool rp2040_hwalarm_trigger_init(struct rp2040_hwalarm_trigger *self,
-                                 enum rp2040_hwalarm_instance alarm_num,
-                                 uint64_t                     fire_at_ns,
-                                 void                         (*cb)(void *),
-                                 void                        *cb_arg) {
-	assert(self);
+static void rp2040_hwtimer_intrhandler(void) {
+	uint irq_num = __get_current_exception() - VTABLE_FIRST_IRQ;
+	enum rp2040_hwalarm_instance alarm_num = TIMER_ALARM_NUM_FROM_IRQ(irq_num);
 	assert(alarm_num < _RP2040_HWALARM_NUM);
+
+	struct rp2040_hwtimer *alarmclock = &hwtimers[alarm_num];
+
+	while (alarmclock->queue &&
+	       NS_TO_US_ROUNDUP(alarmclock->queue->fire_at_ns) <= timer_time_us_64(timer_hw)) {
+		struct alarmclock_trigger *trigger = alarmclock->queue;
+		trigger->cb(trigger->cb_arg);
+		alarmclock->queue = trigger->next;
+		trigger->alarmclock = NULL;
+		trigger->next = NULL;
+		trigger->prev = NULL;
+	}
+
+	hw_clear_bits(&timer_hw->intf, 1 << alarm_num);
+	if (alarmclock->queue)
+		timer_hw->alarm[alarm_num] = (uint32_t)NS_TO_US_ROUNDUP(alarmclock->queue->fire_at_ns);
+}
+
+static bool rp2040_hwtimer_add_trigger(implements_alarmclock     *_alarmclock,
+                                       struct alarmclock_trigger *trigger,
+                                       uint64_t                   fire_at_ns,
+                                       void                       (*cb)(void *),
+                                       void                      *cb_arg) {
+	struct rp2040_hwtimer *alarmclock =
+		VCALL_SELF(struct rp2040_hwtimer, implements_alarmclock, _alarmclock);
+	assert(alarmclock);
+	assert(trigger);
 	assert(fire_at_ns);
 	assert(cb);
 
-	uint64_t fire_at_us = (fire_at_ns + (NS_PER_S/US_PER_S) - 1)/(NS_PER_S/US_PER_S);
-
 	uint64_t now_us = timer_time_us_64(timer_hw);
-	if (fire_at_us > now_us && (fire_at_us - now_us) > UINT32_MAX)
+	if (NS_TO_US_ROUNDUP(fire_at_ns) > now_us &&
+	    (NS_TO_US_ROUNDUP(fire_at_ns) - now_us) > UINT32_MAX)
 		/* Too far in the future.  */
 		return true;
 
-	typeof(alarms[0]) *alarm = &alarms[alarm_num];
-
-	self->alarm      = alarm;
-	self->fire_at_us = fire_at_us;
-	self->cb         = cb;
-	self->cb_arg     = cb_arg;
+	trigger->alarmclock = alarmclock;
+	trigger->fire_at_ns = fire_at_ns;
+	trigger->cb         = cb;
+	trigger->cb_arg     = cb_arg;
 
 	cr_disable_interrupts();
-	struct rp2040_hwalarm_trigger **dst = &alarm->queue;
-	while (*dst && fire_at_us >= (*dst)->fire_at_us)
+	struct alarmclock_trigger **dst = &alarmclock->queue;
+	while (*dst && fire_at_ns >= (*dst)->fire_at_ns)
 		dst = &(*dst)->next;
-	self->next = *dst;
-	self->prev = *dst ? (*dst)->prev : NULL;
+	trigger->next = *dst;
+	trigger->prev = *dst ? (*dst)->prev : NULL;
 	if (*dst)
-		(*dst)->prev = self;
-	*dst = self;
-	if (!alarm->initialized) {
-		hw_set_bits(&timer_hw->inte, 1 << alarm_num);
-		irq_set_exclusive_handler(TIMER_ALARM_IRQ_NUM(timer_hw, alarm_num),
-		                          rp2040_hwalarm_intrhandler);
-		irq_set_enabled(TIMER_ALARM_IRQ_NUM(timer_hw, alarm_num), true);
-		alarm->initialized = true;
+		(*dst)->prev = trigger;
+	*dst = trigger;
+	if (!alarmclock->initialized) {
+		hw_set_bits(&timer_hw->inte, 1 << alarmclock->alarm_num);
+		irq_set_exclusive_handler(TIMER_ALARM_IRQ_NUM(timer_hw, alarmclock->alarm_num),
+		                          rp2040_hwtimer_intrhandler);
+		irq_set_enabled(TIMER_ALARM_IRQ_NUM(timer_hw, alarmclock->alarm_num), true);
+		alarmclock->initialized = true;
 	}
-	if (alarm->queue == self) {
+	if (alarmclock->queue == trigger) {
 		/* Force the interrupt handler to trigger as soon as
 		 * we enable interrupts.  This handles the case of
-		 * when fire_at_us is before when we called
+		 * when fire_at_ns is before when we called
 		 * cr_disable_interrupts().  We could check
 		 * timer_time_us_64() again after calling
 		 * cr_disable_interrupts() and do this conditionally,
 		 * but I don't think that would be any more efficient
 		 * than just letting the interrupt fire.  */
-		hw_set_bits(&timer_hw->intf, 1 << alarm_num);
+		hw_set_bits(&timer_hw->intf, 1 << alarmclock->alarm_num);
 	}
 	cr_enable_interrupts();
 
 	return false;
 }
 
-void rp2040_hwalarm_trigger_cancel(struct rp2040_hwalarm_trigger *self) {
-	assert(self);
+static void rp2040_hwtimer_del_trigger(implements_alarmclock     *_alarmclock,
+                                       struct alarmclock_trigger *trigger) {
+	struct rp2040_hwtimer *alarmclock =
+		VCALL_SELF(struct rp2040_hwtimer, implements_alarmclock, _alarmclock);
+	assert(alarmclock);
+	assert(trigger);
+
 	cr_disable_interrupts();
-	if (self->alarm) {
-		typeof(alarms[0]) *alarm = self->alarm;
-		if (!self->prev)
-			alarm->queue = self->next;
+	if (trigger->alarmclock == alarmclock) {
+		if (!trigger->prev)
+			alarmclock->queue = trigger->next;
 		else
-			self->prev->next = self->next;
-		if (self->next)
-			self->next->prev = self->prev;
-		self->alarm = NULL;
-		self->prev = NULL;
-		self->next = NULL;
+			trigger->prev->next = trigger->next;
+		if (trigger->next)
+			trigger->next->prev = trigger->prev;
+		trigger->alarmclock = NULL;
+		trigger->prev = NULL;
+		trigger->next = NULL;
 	}
 	cr_enable_interrupts();
 }
+
+/* Globals ********************************************************************/
+
+const implements_alarmclock *bootclock = &hwtimers[0];
diff --git a/libhw/rp2040_include/libhw/rp2040_hwalarm.h b/libhw/rp2040_include/libhw/rp2040_hwalarm.h
deleted file mode 100644
index 3a7ae10..0000000
--- a/libhw/rp2040_include/libhw/rp2040_hwalarm.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/* libhw/rp2040_hwalarm.h - Alarms for the RP2040
- *
- * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
- * SPDX-License-Identifier: AGPL-3.0-or-later
- */
-
-#ifndef _LIBHW_RP2040_HWALARM_H_
-#define _LIBHW_RP2040_HWALARM_H_
-
-#include <stdbool.h>         /* for bool */
-#include <stdint.h>          /* for uint{n}_t */
-
-#include <libmisc/private.h> /* for BEGIN_PRIVATE, END_PRIVATE */
-
-/**
- * The RP2040 has one system "timer" (which we also use for
- * ./rp2040_bootclock.c) with 4 alarm interrupts.
- */
-enum rp2040_hwalarm_instance {
-	RP2040_HWALARM_0 = 0,
-	RP2040_HWALARM_1 = 1,
-	RP2040_HWALARM_2 = 2,
-	RP2040_HWALARM_3 = 3,
-	_RP2040_HWALARM_NUM,
-};
-
-struct rp2040_hwalarm_trigger;
-struct rp2040_hwalarm_trigger {
-	BEGIN_PRIVATE(LIBHW_RP2040_HWALARM_H)
-	void                              *alarm;
-	struct rp2040_hwalarm_trigger     *prev, *next;
-
-	uint64_t                           fire_at_us;
-	void                               (*cb)(void *);
-	void                              *cb_arg;
-	END_PRIVATE(LIBHW_RP2040_HWALARM_H)
-};
-
-/**
- * Returns true on error.
- *
- * fire_at_ns must be at most UINT32_MAX µs (72 minutes) in the future
- * (or an error will be returned).
- *
- * If fire_at_ns is in the past, then it will fire immediately.
- */
-bool rp2040_hwalarm_trigger_init(struct rp2040_hwalarm_trigger *self,
-                                 enum rp2040_hwalarm_instance alarm_num,
-                                 uint64_t                     fire_at_ns,
-                                 void                         (*cb)(void *),
-                                 void                        *cb_arg);
-
-void rp2040_hwalarm_trigger_cancel(struct rp2040_hwalarm_trigger *self);
-
-#endif /* _LIBHW_RP2040_HWALARM_H_ */
diff --git a/libhw/rp2040_include/libhw/rp2040_hwspi.h b/libhw/rp2040_include/libhw/rp2040_hwspi.h
index 8d90dbb..19fb4ba 100644
--- a/libhw/rp2040_include/libhw/rp2040_hwspi.h
+++ b/libhw/rp2040_include/libhw/rp2040_hwspi.h
@@ -1,5 +1,4 @@
-/* libhw/rp2040_hwspi.h - `implements_spi` implementation for the RP2040's
- *                        ARM Primecell SSP (PL022) (header file)
+/* libhw/rp2040_hwspi.h - <libhw/generic/spi.h> implementation for the RP2040's ARM Primecell SSP (PL022)
  *
  * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
  * SPDX-License-Identifier: AGPL-3.0-or-later
diff --git a/libhw/rp2040_include/libhw/rp2040_hwtimer.h b/libhw/rp2040_include/libhw/rp2040_hwtimer.h
new file mode 100644
index 0000000..0885edf
--- /dev/null
+++ b/libhw/rp2040_include/libhw/rp2040_hwtimer.h
@@ -0,0 +1,26 @@
+/* libhw/rp2040_hwtimer.h - <libhw/generic/alarmclock.h> implementation for the RP2040's hardware timer
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _LIBHW_RP2040_HWALARM_H_
+#define _LIBHW_RP2040_HWALARM_H_
+
+#include <libhw/generic/alarmclock.h>
+
+/**
+ * The RP2040 has one system "timer" (which we also use for
+ * ./rp2040_bootclock.c) with 4 alarm interrupts.
+ */
+enum rp2040_hwalarm_instance {
+	RP2040_HWALARM_0 = 0,
+	RP2040_HWALARM_1 = 1,
+	RP2040_HWALARM_2 = 2,
+	RP2040_HWALARM_3 = 3,
+	_RP2040_HWALARM_NUM,
+};
+
+implements_alarmclock *rp2040_hwtimer(enum rp2040_hwalarm_instance alarm_num);
+
+#endif /* _LIBHW_RP2040_HWALARM_H_ */