hw/core: Add documentation and license comments to reset.h

Add the usual boilerplate license/copyright comment to reset.h (using
the text from reset.c), and document the existing functions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20240220160622.114437-6-peter.maydell@linaro.org

include/sysemu/reset.h

@@ -1,3 +1,29 @@
+/*
+ *  Reset handlers.
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ * Copyright (c) 2016 Red Hat, Inc.
+ * Copyright (c) 2024 Linaro, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
 #ifndef QEMU_SYSEMU_RESET_H
 #define QEMU_SYSEMU_RESET_H
 
@@ -5,9 +31,62 @@
 
 typedef void QEMUResetHandler(void *opaque);
 
+/**
+ * qemu_register_reset: Register a callback for system reset
+ * @func: function to call
+ * @opaque: opaque data to pass to @func
+ *
+ * Register @func on the list of functions which are called when the
+ * entire system is reset. The functions are called in the order in
+ * which they are registered.
+ *
+ * In general this function should not be used in new code where possible;
+ * for instance, device model reset is better accomplished using the
+ * methods on DeviceState.
+ *
+ * It is not permitted to register or unregister reset functions from
+ * within the @func callback.
+ *
+ * We assume that the caller holds the BQL.
+ */
 void qemu_register_reset(QEMUResetHandler *func, void *opaque);
+
+/**
+ * qemu_register_reset_nosnapshotload: Register a callback for system reset
+ * @func: function to call
+ * @opaque: opaque data to pass to @func
+ *
+ * This is the same as qemu_register_reset(), except that @func is
+ * not called if the reason that the system is being reset is to
+ * put it into a clean state prior to loading a snapshot (i.e. for
+ * SHUTDOWN_CAUSE_SNAPSHOT_LOAD).
+ */
 void qemu_register_reset_nosnapshotload(QEMUResetHandler *func, void *opaque);
+
+/**
+ * qemu_unregister_reset: Unregister a system reset callback
+ * @func: function registered with qemu_register_reset()
+ * @opaque: the same opaque data that was passed to qemu_register_reset()
+ *
+ * Undo the effects of a qemu_register_reset(). The @func and @opaque
+ * must both match the arguments originally used with qemu_register_reset().
+ *
+ * We assume that the caller holds the BQL.
+ */
 void qemu_unregister_reset(QEMUResetHandler *func, void *opaque);
+
+/**
+ * qemu_devices_reset: Perform a complete system reset
+ * @reason: reason for the reset
+ *
+ * This function performs the low-level work needed to do a complete reset
+ * of the system (calling all the callbacks registered with
+ * qemu_register_reset()). It should only be called by the code in a
+ * MachineClass reset method.
+ *
+ * If you want to trigger a system reset from, for instance, a device
+ * model, don't use this function. Use qemu_system_reset_request().
+ */
 void qemu_devices_reset(ShutdownCause reason);
 
 #endif