kern: fs: Add initial devfs implementation

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

5 files changed, 276 insertions, 1 deletions

diff --git a/src/sys/fs/devfs.c b/src/sys/fs/devfs.c
new file mode 100644
index 0000000..7553003
--- /dev/null
+++ b/src/sys/fs/devfs.c
@@ -0,0 +1,166 @@
+/*
+ * 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.
+ */
+
+/*
+ * Description: Device filesystem
+ * Author: Ian Marco Moffett
+ */
+
+#include <sys/errno.h>
+#include <sys/mount.h>
+#include <sys/syslog.h>
+#include <os/vnode.h>
+#include <os/kalloc.h>
+#include <fs/devfs.h>
+#include <string.h>
+
+static struct vop devfs_vops;
+static TAILQ_HEAD(, devfs_node) nodelist;
+
+/*
+ * Find a node within the device filesystem
+ */
+static int
+devfs_lookup(struct vop_lookup_args *args)
+{
+    int error;
+    struct devfs_node *dnp = NULL;
+    struct vnode *vp;
+
+    if (args == NULL) {
+        return -EINVAL;
+    }
+
+    /* Need a pointer to write the result */
+    if (args->vpp == NULL) {
+        return -EINVAL;
+    }
+
+    TAILQ_FOREACH(dnp, &nodelist, link) {
+        if (dnp == NULL) {
+            continue;
+        }
+
+        if (strcmp(dnp->name, args->name) != 0) {
+            continue;
+        }
+
+        /* Found it! Create a vnode */
+        error = vfs_valloc(&vp, VTYPE_FILE, 0);
+        if (error < 0) {
+            return error;
+        }
+
+        vp->data = dnp;
+        *args->vpp = vp;
+        return 0;
+    }
+
+    return -ENOENT;
+}
+
+/*
+ * Register a new device to devfs
+ */
+int
+devfs_register(const char *name, dev_type_t type, void *devsw, int flags)
+{
+    struct devfs_node *dnp;
+    size_t devname_len;
+    struct vop_lookup_args args;
+    struct vnode *vp;
+
+    if (name == NULL || devsw == NULL) {
+        return -EINVAL;
+    }
+
+    if (type >= __DEVFS_NTYPE) {
+        return -EINVAL;
+    }
+
+    dnp = kalloc(sizeof(*dnp));
+    if (dnp == NULL) {
+        return -ENOMEM;
+    }
+
+    switch (type) {
+    case DEVFS_NONE:
+    case DEVFS_CDEV:
+        dnp->type = type;
+        break;
+    }
+
+    devname_len = strlen(name);
+    memcpy(dnp->name, name, devname_len);
+    TAILQ_INSERT_TAIL(&nodelist, dnp, link);
+    return 0;
+}
+
+/*
+ * Initialize the device filesystem
+ */
+static int
+devfs_init(struct fs_info *fip)
+{
+    (void)fip;
+    TAILQ_INIT(&nodelist);
+    return 0;
+}
+
+/*
+ * Mount the device filesystem
+ */
+static int
+devfs_mount(struct fs_info *fip, struct mount_args *margs)
+{
+    int error;
+    struct vnode *vp;
+
+    if (fip == NULL || margs == NULL) {
+        return -1;
+    }
+
+    error = vfs_valloc(&margs->vp_res, VTYPE_DIR, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    vp = margs->vp_res;
+    vp->vops = &devfs_vops;
+    return 0;
+}
+
+static struct vop devfs_vops = {
+    .lookup = devfs_lookup
+};
+
+struct vfsops g_devfs_vfops = {
+    .init = devfs_init,
+    .mount = devfs_mount
+};
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_ */
diff --git a/src/sys/include/sys/mount.h b/src/sys/include/sys/mount.h
index dbd8d53..4e39279 100644
--- a/src/sys/include/sys/mount.h
+++ b/src/sys/include/sys/mount.h
@@ -46,6 +46,7 @@
  * Mount filesystem string names
  */
 #define MOUNT_INITRD "initrd"   /* Initial ramdisk */
+#define MOUNT_DEVFS  "devfs"    /* Device filesystem */
 
 /* Forward declarations */
 struct fs_info;
@@ -54,6 +55,7 @@ struct mount;
 
 /* Filesystem vfsops */
 extern struct vfsops g_omar_vfsops;
+extern struct vfsops g_devfs_vfops;
 
 /*
  * Represents a mountpoint
diff --git a/src/sys/os/Makefile b/src/sys/os/Makefile
index de73afd..da481ec 100644
--- a/src/sys/os/Makefile
+++ b/src/sys/os/Makefile
@@ -12,6 +12,7 @@ CFILES += $(shell find ../lib -name "*.c")
 CFILES += $(shell find ../io -name "*.c")
 CFILES += $(shell find ../acpi -name "*.c")
 CFILES += $(shell find ../compat -name "*.c")
+CFILES += $(shell find ../fs -name "*.c")
 
 DEPS = $(CFILES:.c=.d)
 OBJECTS = $(CFILES:%.c=%.o)
diff --git a/src/sys/os/vfs_init.c b/src/sys/os/vfs_init.c
index 92d7b94..80d8559 100644
--- a/src/sys/os/vfs_init.c
+++ b/src/sys/os/vfs_init.c
@@ -38,7 +38,8 @@
  * The filesystem table
  */
 static struct fs_info fstab[] = {
-    { MOUNT_INITRD, &g_omar_vfsops, 0 }
+    { MOUNT_INITRD, &g_omar_vfsops, 0 },
+    { MOUNT_DEVFS, &g_devfs_vfops, 0 }
 };
 
 /*