virtio: extract iothread-vq-mapping.h API

The code that builds an array of AioContext pointers indexed by the
virtqueue is not specific to virtio-blk. virtio-scsi will need to do the
same thing, so extract the functions.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250311132616.1049687-11-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/hw/virtio/iothread-vq-mapping.h

@@ -0,0 +1,45 @@
+/*
+ * IOThread Virtqueue Mapping
+ *
+ * Copyright Red Hat, Inc
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#ifndef HW_VIRTIO_IOTHREAD_VQ_MAPPING_H
+#define HW_VIRTIO_IOTHREAD_VQ_MAPPING_H
+
+#include "qapi/error.h"
+#include "qapi/qapi-types-virtio.h"
+
+/**
+ * iothread_vq_mapping_apply:
+ * @list: The mapping of virtqueues to IOThreads.
+ * @vq_aio_context: The array of AioContext pointers to fill in.
+ * @num_queues: The length of @vq_aio_context.
+ * @errp: If an error occurs, a pointer to the area to store the error.
+ *
+ * Fill in the AioContext for each virtqueue in the @vq_aio_context array given
+ * the iothread-vq-mapping parameter in @list.
+ *
+ * iothread_vq_mapping_cleanup() must be called to free IOThread object
+ * references after this function returns success.
+ *
+ * Returns: %true on success, %false on failure.
+ **/
+bool iothread_vq_mapping_apply(
+        IOThreadVirtQueueMappingList *list,
+        AioContext **vq_aio_context,
+        uint16_t num_queues,
+        Error **errp);
+
+/**
+ * iothread_vq_mapping_cleanup:
+ * @list: The mapping of virtqueues to IOThreads.
+ *
+ * Release IOThread object references that were acquired by
+ * iothread_vq_mapping_apply().
+ */
+void iothread_vq_mapping_cleanup(IOThreadVirtQueueMappingList *list);
+
+#endif /* HW_VIRTIO_IOTHREAD_VQ_MAPPING_H */