kernel: fs: Introduce ctlfs

ctlfs (Control FS) is a filesystem aimed to provide configuration of
devices separate from their respective devices files. Most UNIX-like
systems rely on the ioctl() mechanism for sending commands to device
drivers, while this certainly works, it is important to realize how
messy it can get having massive switch cases per driver. ctlfs fixes
this by giving each device a "node" in ctlfs that contains several
control files.

For example, imagine we have a SCSI device (/dev/sd1). Its ctlfs
counterpart would be a directory at /ctl/sd1/. For an hdd this may
contain files such as:

/ctl/sd1/bsize   # Block size if read (mode [rwx]: -w-)
/ctl/sd1/cmd     # Command if written, status if read (mode [rwx]: rw-)
... et cetera

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

1 files changed, 62 insertions, 0 deletions

diff --git a/sys/include/fs/ctlfs.h b/sys/include/fs/ctlfs.h
new file mode 100644
index 0000000..582421c
--- /dev/null
+++ b/sys/include/fs/ctlfs.h
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * 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 Hyra 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_CTLFS_H_
+#define _FS_CTLFS_H_
+
+struct ctlfs_dev;
+
+struct ctlops {
+    int(*read)(struct ctlfs_dev *cdp, struct sio_txn *sio);
+    int(*write)(struct ctlfs_dev *cdp, struct sio_txn *sio);
+};
+
+/*
+ * Ctlfs op arguments
+ *
+ * @devname: Device name.
+ * @major: Device major
+ * @minor: Device minor.
+ * @mode: Access flags.
+ * @devname [1]: Device name (node name)
+ * @ctlname: [1]: Control name (node entry name)
+ */
+struct ctlfs_dev {
+    union {
+        const char *devname;
+        const char *ctlname;
+    };
+    const struct ctlops *ops;
+    mode_t mode;
+};
+
+int ctlfs_create_node(const char *name, const struct ctlfs_dev *dp);
+int ctlfs_create_entry(const char *name, const struct ctlfs_dev *dp);
+
+#endif  /* !_FS_CTLFS_H_ */