kernel: Add timer abstraction

This commit introduces a new timer abstraction that is architecture-independent.
It enables the registration and request of timers in a consistent and uniform manner
abstracting away architectural details.

Signed-off-by: sigsegv7 <ian@vegaa.systems>

1 files changed, 112 insertions, 0 deletions

diff --git a/sys/kern/kern_timer.c b/sys/kern/kern_timer.c
new file mode 100644
index 0000000..fab06ce
--- /dev/null
+++ b/sys/kern/kern_timer.c
@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2023 Ian Marco Moffett and the VegaOS team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of VegaOS nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/timer.h>
+
+/*
+ * When a timer on the machine has been registered
+ * to the Vega kernel, they'll be added to the Vega timer
+ * registry.
+ */
+static const struct timer *tmr_registry[TIMER_ID_COUNT] = { 0 };
+
+/*
+ * Returns true if the timer ID given
+ * is valid.
+ *
+ * @id: ID to verify.
+ */
+static inline bool
+is_timer_id_valid(timer_id_t id)
+{
+    return id < TIMER_ID_COUNT;
+}
+
+/*
+ * Adds timer on the machine to the timer registry. To be specific,
+ * this function writes information about the specific timer to the
+ * timer registry. However, it will not overwrite an entry. To do this
+ * you must use tmr_registry_overwrite(), of course with caution.
+ *
+ * @id: ID of timer to register.
+ * @tmr: Timer descriptor to register.
+ */
+tmrr_status_t
+register_timer(timer_id_t id, const struct timer *tmr)
+{
+    if (!is_timer_id_valid(id))
+        return TMRR_INVALID_TYPE;
+
+    if (tmr_registry[id] != NULL)
+        return TMRR_HAS_ENTRY;
+
+    tmr_registry[id] = tmr;
+    return TMRR_SUCCESS;
+}
+
+/*
+ * Overwrites an entry within the timer registery.
+ * Use with caution.
+ *
+ * @id: ID of entry to overwrite.
+ * @tmr: Timer descriptor to write.
+ */
+tmrr_status_t
+tmr_registry_overwrite(timer_id_t id, const struct timer *tmr)
+{
+    if (!is_timer_id_valid(id))
+        return TMRR_INVALID_TYPE;
+
+    tmr_registry[id] = tmr;
+    return TMRR_SUCCESS;
+}
+
+/*
+ * Requests a specific timer descriptor
+ * with a specific ID.
+ *
+ * @id: ID to request.
+ * @tmr_out: Pointer to memory that'll hold the
+ *           requested descriptor.
+ */
+tmrr_status_t
+req_timer(timer_id_t id, struct timer *tmr_out)
+{
+    if (!is_timer_id_valid(id))
+        return TMRR_INVALID_TYPE;
+
+    if (tmr_registry[id] == NULL)
+        return TMRR_EMPTY_ENTRY;
+
+    if (tmr_out == NULL)
+        return TMRR_INVALID_ARG;
+
+    *tmr_out = *tmr_registry[id];
+    return TMRR_SUCCESS;
+}