os: introduce C-API to Genode services

This commit introduces a C-API to the Uplink session, as well as to
serve as a Block service. It can be used by drivers ported from
C-only projects, like the Linux kernel, or BSD kernels for instance.

Fix #4226

repos/os/include/genode_c_api/block.h

@@ -0,0 +1,102 @@
+/*
+ * \brief  C-API Genode block backend
+ * \author Stefan Kalkowski
+ * \date   2021-07-05
+ */
+
+/*
+ * Copyright (C) 2006-2021 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _GENODE_C_API__BLOCK_H_
+#define _GENODE_C_API__BLOCK_H_
+
+#include <genode_c_api/base.h>
+
+
+struct genode_block_session; /* definition is private to the implementation */
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/********************
+ ** Initialization **
+ ********************/
+
+/**
+ * Callback called during peer session request to allocate dma-capable shared buffer
+ */
+typedef struct genode_attached_dataspace * (*genode_block_alloc_peer_buffer_t)
+	(unsigned long size);
+
+/**
+ * Callback called when closing peer session to free shared buffer
+ */
+typedef void (*genode_block_free_peer_buffer_t)
+	(struct genode_attached_dataspace * ds);
+
+/**
+ * Initialize block root component
+ *
+ * \param handler  signal handler to be installed at each block session
+ */
+void genode_block_init(struct genode_env            *env,
+                       struct genode_allocator      *alloc,
+                       struct genode_signal_handler *handler,
+                       genode_block_alloc_peer_buffer_t,
+                       genode_block_free_peer_buffer_t);
+
+
+/**************************************
+ ** Block device lifetime management **
+ **************************************/
+
+typedef unsigned long long genode_block_sector_t;
+
+void genode_block_announce_device(const char *          name,
+                                  genode_block_sector_t sectors,
+                                  int                   writeable);
+
+void genode_block_discontinue_device(const char * name);
+
+
+/************************************
+ ** Block session request handling **
+ ************************************/
+
+enum Operation {
+	GENODE_BLOCK_READ,
+	GENODE_BLOCK_WRITE,
+	GENODE_BLOCK_SYNC,
+	GENODE_BLOCK_UNAVAIL,
+};
+
+struct genode_block_request {
+	int                   op;
+	genode_block_sector_t blk_nr;
+	genode_block_sector_t blk_cnt;
+	void *                addr;
+};
+
+struct genode_block_session * genode_block_session_by_name(const char * name);
+
+struct genode_block_request *
+genode_block_request_by_session(struct genode_block_session * const session);
+
+void genode_block_ack_request(struct genode_block_session * const session,
+                              struct genode_block_request * const request,
+                              int success);
+
+void genode_block_notify_peers(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _GENODE_C_API__BLOCK_H_ */