debugfs: add 9p device interface

The 9p interface provides abstraction layers allowing the software
that uses devices to be independent from the hardware.

This patch provides a file system abstraction to link drivers to their
devices and propose a common interface to expose driver operations to
higher layers. This file system can be used to access and configure a
device by doing read/write operations.

Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Ia9662393baf489855dc0c8f389fe4a0afbc9c255

1 files changed, 60 insertions, 0 deletions

diff --git a/include/lib/debugfs.h b/include/lib/debugfs.h
new file mode 100644
index 000000000..b7e33303c
--- /dev/null
+++ b/include/lib/debugfs.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2019, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef DEBUGFS_H
+#define DEBUGFS_H
+
+#define NAMELEN   13 /* Maximum length of a file name */
+#define PATHLEN   41 /* Maximum length of a path */
+#define STATLEN   41 /* Size of static part of dir format */
+#define ROOTLEN   (2 + 4) /* Size needed to encode root string */
+#define FILNAMLEN (2 + NAMELEN) /* Size needed to encode filename */
+#define DIRLEN    (STATLEN + FILNAMLEN + 3*ROOTLEN) /* Size of dir entry */
+
+#define KSEEK_SET 0
+#define KSEEK_CUR 1
+#define KSEEK_END 2
+
+#define NELEM(tab) (sizeof(tab) / sizeof((tab)[0]))
+
+typedef unsigned short qid_t; /* FIXME: short type not recommended? */
+
+/*******************************************************************************
+ * This structure contains the necessary information to represent a 9p
+ * directory.
+ ******************************************************************************/
+typedef struct {
+	char		name[NAMELEN];
+	long		length;
+	unsigned char	mode;
+	unsigned char	index;
+	unsigned char	dev;
+	qid_t		qid;
+} dir_t;
+
+/* Permission definitions used as flags */
+#define O_READ		(1 << 0)
+#define O_WRITE		(1 << 1)
+#define O_RDWR		(1 << 2)
+#define O_BIND		(1 << 3)
+#define O_DIR		(1 << 4)
+#define O_STAT		(1 << 5)
+
+/* 9p interface */
+int mount(const char *srv, const char *mnt, const char *spec);
+int create(const char *name, int flags);
+int open(const char *name, int flags);
+int close(int fd);
+int read(int fd, void *buf, int n);
+int write(int fd, void *buf, int n);
+int seek(int fd, long off, int whence);
+int bind(const char *path, const char *where);
+int stat(const char *path, dir_t *dir);
+
+/* DebugFS initialization */
+void debugfs_init(void);
+
+#endif /* DEBUGFS_H */