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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Copyright (C) 2026 Richard Qin */
/*
* devfs.cc — /dev population and chardev-aware open
*
* Creates /dev as a subdirectory under the ramfs root, then
* populates device nodes. On open(), if the inode is S_IFCHR,
* we look up the cdev by i_rdev and use its fops.
*/
#include <lume/fs.h>
#include <lume/dcache.h>
#include <lume/file.h>
#include <lume/chardev.h>
#include <lume/mount.h>
#include <lume/klog.h>
#include <lume/errno.h>
#include <lume/fs_types.h>
/* ================================================================== */
/* devfs_create_node — create a char device inode under parent */
/* ================================================================== */
static int devfs_create_node(dentry* parent, const char* name,
uint32 major, uint32 minor)
{
inode* dir_ip = parent->d_inode;
if (!dir_ip || !dir_ip->i_op || !dir_ip->i_op->mknod) {
return -EPERM;
}
qstr q{};
q.name = name;
q.len = 0;
for (const char* s = name; *s; s++) {
q.len++;
}
dentry* de = d_alloc(parent, &q);
if (!de) {
return -ENOMEM;
}
int err = dir_ip->i_op->mknod(dir_ip, de, S_IFCHR | 0666,
MKDEV(major, minor));
if (err) {
return err;
}
return 0;
}
/* ================================================================== */
/* devfs_open — chardev-aware open hook */
/* ================================================================== */
/*
* Called from sys_openat when the inode is S_IFCHR.
* Replaces f_op with the chardev's file_operations.
*/
int devfs_chrdev_open(inode* ip, file* fp)
{
if (!S_ISCHR(ip->i_mode)) {
return 0;
}
cdev* cd = cdev_find(ip->i_rdev);
if (!cd || !cd->fops) {
return -ENXIO; /* No such device */
}
fp->f_op = cd->fops;
/* Call the device's own open if it has one */
if (fp->f_op->open) {
return fp->f_op->open(ip, fp);
}
return 0;
}
/* ================================================================== */
/* devfs_init — create /dev and populate device nodes */
/* ================================================================== */
void devfs_init()
{
if (!g_root_dentry || !g_root_dentry->d_inode) {
printk(KERN_ERR "[devfs] no root filesystem!\n");
return;
}
/* Create /dev directory — or reuse if initramfs already created it.
* Linux: devtmpfs similarly handles pre-existing directories. */
inode* root_ip = g_root_dentry->d_inode;
qstr dev_name{};
dev_name.name = "dev";
dev_name.len = 3;
dev_name.hash = full_name_hash("dev", 3);
dentry* dev_de = d_lookup(g_root_dentry, &dev_name);
if (dev_de) {
/* /dev already exists (from initramfs) — reuse it */
printk("[devfs] reusing existing /dev directory\n");
} else {
/* Create /dev from scratch */
if (!root_ip->i_op || !root_ip->i_op->mkdir) {
printk(KERN_ERR "[devfs] root has no mkdir!\n");
return;
}
dev_de = d_alloc(g_root_dentry, &dev_name);
if (!dev_de) {
printk(KERN_ERR "[devfs] failed to alloc /dev dentry\n");
return;
}
int err = root_ip->i_op->mkdir(root_ip, dev_de, S_IFDIR | 0755);
if (err) {
printk(KERN_ERR "[devfs] mkdir /dev failed: %d\n", err);
return;
}
}
/* Populate: /dev/console (5,1) */
devfs_create_node(dev_de, "console", 5, 1);
/* Populate: /dev/null (1,3) */
devfs_create_node(dev_de, "null", 1, 3);
/* Populate: /dev/zero (1,5) */
devfs_create_node(dev_de, "zero", 1, 5);
printk("[devfs] /dev populated (console, null, zero)\n");
}
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