kern: fs: Add initial devfs implementation

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 105 insertions, 0 deletions

diff --git a/src/sys/include/fs/devfs.h b/src/sys/include/fs/devfs.h
new file mode 100644
index 0000000..ea96cdd
--- /dev/null
+++ b/src/sys/include/fs/devfs.h
@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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.
+ */
+
+#ifndef _FS_DEVFS_H_
+#define _FS_DEVFS_H_
+
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <sys/limits.h>
+#include <os/vnode.h>
+
+/* Forward declarations */
+struct devfs_node;
+
+/*
+ * Represents an I/O buffer for device files
+ * on the system
+ */
+struct dev_iobuf {
+    void *buf;
+    size_t count;
+};
+
+/*
+ * Character device descriptor and hooks
+ *
+ * @read: Read n bytes from the char device
+ * @write: Write n bytes from the char device
+ */
+struct cdevsw {
+    ssize_t(*read)(struct devfs_node *dnp, struct dev_iobuf *iob, int flags);
+    ssize_t(*write)(struct devfs_node *dnp, struct dev_iobuf *iob, int flags);
+};
+
+/*
+ * Describes the device node types
+ *
+ * @DEVFS_NONE: No type
+ * @DEVFS_CDEV: Char device
+ */
+typedef enum {
+    DEVFS_NONE,
+    DEVFS_CDEV,
+    __DEVFS_NTYPE
+} dev_type_t;
+
+/*
+ * Represents a device filesystem node
+ *
+ * @name: Name of device node
+ * @type: Node type
+ * @cdev: Character device (if DEVFS_CDEV)
+ * @link: Queue link
+ */
+struct devfs_node {
+    char name[NAME_MAX];
+    dev_type_t type;
+    union {
+        struct cdevsw *cdev;
+        void *dev;
+    };
+
+    TAILQ_ENTRY(devfs_node) link;
+};
+
+/*
+ * Register a character device
+ *
+ * @name: Name of character device
+ * @type: Device type to use
+ * @cdev: Character device operations to use
+ * @flags: Optional flags
+ *
+ * Returns zero on success, otherwise a less than zero
+ * value on failure.
+ */
+int devfs_register(const char *name, dev_type_t type, void *devsw, int flags);
+
+#endif  /* !_FS_DEVFS_H_ */