v4.19.13 snapshot.
diff --git a/drivers/char/misc.c b/drivers/char/misc.c
new file mode 100644
index 0000000..53cfe57
--- /dev/null
+++ b/drivers/char/misc.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/drivers/char/misc.c
+ *
+ * Generic misc open routine by Johan Myreen
+ *
+ * Based on code from Linus
+ *
+ * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
+ * changes incorporated into 0.97pl4
+ * by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
+ * See busmouse.c for particulars.
+ *
+ * Made things a lot mode modular - easy to compile in just one or two
+ * of the misc drivers, as they are now completely independent. Linus.
+ *
+ * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
+ *
+ * Fixed a failing symbol register to free the device registration
+ * Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
+ *
+ * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
+ *
+ * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
+ *
+ * Handling of mouse minor numbers for kerneld:
+ * Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
+ * adapted by Bjorn Ekwall <bj0rn@blox.se>
+ * corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
+ *
+ * Changes for kmod (from kerneld):
+ * Cyrus Durgin <cider@speakeasy.org>
+ *
+ * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
+ */
+
+#include <linux/module.h>
+
+#include <linux/fs.h>
+#include <linux/errno.h>
+#include <linux/miscdevice.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/mutex.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/stat.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/tty.h>
+#include <linux/kmod.h>
+#include <linux/gfp.h>
+
+/*
+ * Head entry for the doubly linked miscdevice list
+ */
+static LIST_HEAD(misc_list);
+static DEFINE_MUTEX(misc_mtx);
+
+/*
+ * Assigned numbers, used for dynamic minors
+ */
+#define DYNAMIC_MINORS 64 /* like dynamic majors */
+static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
+
+#ifdef CONFIG_PROC_FS
+static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
+{
+ mutex_lock(&misc_mtx);
+ return seq_list_start(&misc_list, *pos);
+}
+
+static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+ return seq_list_next(v, &misc_list, pos);
+}
+
+static void misc_seq_stop(struct seq_file *seq, void *v)
+{
+ mutex_unlock(&misc_mtx);
+}
+
+static int misc_seq_show(struct seq_file *seq, void *v)
+{
+ const struct miscdevice *p = list_entry(v, struct miscdevice, list);
+
+ seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
+ return 0;
+}
+
+
+static const struct seq_operations misc_seq_ops = {
+ .start = misc_seq_start,
+ .next = misc_seq_next,
+ .stop = misc_seq_stop,
+ .show = misc_seq_show,
+};
+#endif
+
+static int misc_open(struct inode *inode, struct file *file)
+{
+ int minor = iminor(inode);
+ struct miscdevice *c;
+ int err = -ENODEV;
+ const struct file_operations *new_fops = NULL;
+
+ mutex_lock(&misc_mtx);
+
+ list_for_each_entry(c, &misc_list, list) {
+ if (c->minor == minor) {
+ new_fops = fops_get(c->fops);
+ break;
+ }
+ }
+
+ if (!new_fops) {
+ mutex_unlock(&misc_mtx);
+ request_module("char-major-%d-%d", MISC_MAJOR, minor);
+ mutex_lock(&misc_mtx);
+
+ list_for_each_entry(c, &misc_list, list) {
+ if (c->minor == minor) {
+ new_fops = fops_get(c->fops);
+ break;
+ }
+ }
+ if (!new_fops)
+ goto fail;
+ }
+
+ /*
+ * Place the miscdevice in the file's
+ * private_data so it can be used by the
+ * file operations, including f_op->open below
+ */
+ file->private_data = c;
+
+ err = 0;
+ replace_fops(file, new_fops);
+ if (file->f_op->open)
+ err = file->f_op->open(inode, file);
+fail:
+ mutex_unlock(&misc_mtx);
+ return err;
+}
+
+static struct class *misc_class;
+
+static const struct file_operations misc_fops = {
+ .owner = THIS_MODULE,
+ .open = misc_open,
+ .llseek = noop_llseek,
+};
+
+/**
+ * misc_register - register a miscellaneous device
+ * @misc: device structure
+ *
+ * Register a miscellaneous device with the kernel. If the minor
+ * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
+ * and placed in the minor field of the structure. For other cases
+ * the minor number requested is used.
+ *
+ * The structure passed is linked into the kernel and may not be
+ * destroyed until it has been unregistered. By default, an open()
+ * syscall to the device sets file->private_data to point to the
+ * structure. Drivers don't need open in fops for this.
+ *
+ * A zero is returned on success and a negative errno code for
+ * failure.
+ */
+
+int misc_register(struct miscdevice *misc)
+{
+ dev_t dev;
+ int err = 0;
+ bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
+
+ INIT_LIST_HEAD(&misc->list);
+
+ mutex_lock(&misc_mtx);
+
+ if (is_dynamic) {
+ int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
+
+ if (i >= DYNAMIC_MINORS) {
+ err = -EBUSY;
+ goto out;
+ }
+ misc->minor = DYNAMIC_MINORS - i - 1;
+ set_bit(i, misc_minors);
+ } else {
+ struct miscdevice *c;
+
+ list_for_each_entry(c, &misc_list, list) {
+ if (c->minor == misc->minor) {
+ err = -EBUSY;
+ goto out;
+ }
+ }
+ }
+
+ dev = MKDEV(MISC_MAJOR, misc->minor);
+
+ misc->this_device =
+ device_create_with_groups(misc_class, misc->parent, dev,
+ misc, misc->groups, "%s", misc->name);
+ if (IS_ERR(misc->this_device)) {
+ if (is_dynamic) {
+ int i = DYNAMIC_MINORS - misc->minor - 1;
+
+ if (i < DYNAMIC_MINORS && i >= 0)
+ clear_bit(i, misc_minors);
+ misc->minor = MISC_DYNAMIC_MINOR;
+ }
+ err = PTR_ERR(misc->this_device);
+ goto out;
+ }
+
+ /*
+ * Add it to the front, so that later devices can "override"
+ * earlier defaults
+ */
+ list_add(&misc->list, &misc_list);
+ out:
+ mutex_unlock(&misc_mtx);
+ return err;
+}
+
+/**
+ * misc_deregister - unregister a miscellaneous device
+ * @misc: device to unregister
+ *
+ * Unregister a miscellaneous device that was previously
+ * successfully registered with misc_register().
+ */
+
+void misc_deregister(struct miscdevice *misc)
+{
+ int i = DYNAMIC_MINORS - misc->minor - 1;
+
+ if (WARN_ON(list_empty(&misc->list)))
+ return;
+
+ mutex_lock(&misc_mtx);
+ list_del(&misc->list);
+ device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
+ if (i < DYNAMIC_MINORS && i >= 0)
+ clear_bit(i, misc_minors);
+ mutex_unlock(&misc_mtx);
+}
+
+EXPORT_SYMBOL(misc_register);
+EXPORT_SYMBOL(misc_deregister);
+
+static char *misc_devnode(struct device *dev, umode_t *mode)
+{
+ struct miscdevice *c = dev_get_drvdata(dev);
+
+ if (mode && c->mode)
+ *mode = c->mode;
+ if (c->nodename)
+ return kstrdup(c->nodename, GFP_KERNEL);
+ return NULL;
+}
+
+static int __init misc_init(void)
+{
+ int err;
+ struct proc_dir_entry *ret;
+
+ ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
+ misc_class = class_create(THIS_MODULE, "misc");
+ err = PTR_ERR(misc_class);
+ if (IS_ERR(misc_class))
+ goto fail_remove;
+
+ err = -EIO;
+ if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
+ goto fail_printk;
+ misc_class->devnode = misc_devnode;
+ return 0;
+
+fail_printk:
+ pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
+ class_destroy(misc_class);
+fail_remove:
+ if (ret)
+ remove_proc_entry("misc", NULL);
+ return err;
+}
+subsys_initcall(misc_init);