1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * In some cases UART attached devices which require an in kernel driver,
4 * e.g. UART attached Bluetooth HCIs are described in the ACPI tables
5 * by an ACPI device with a broken or missing UartSerialBusV2() resource.
6 *
7 * This causes the kernel to create a /dev/ttyS# char-device for the UART
8 * instead of creating an in kernel serdev-controller + serdev-device pair
9 * for the in kernel driver.
10 *
11 * The quirk handling in acpi_quirk_skip_serdev_enumeration() makes the kernel
12 * create a serdev-controller device for these UARTs instead of a /dev/ttyS#.
13 *
14 * Instantiating the actual serdev-device to bind to is up to pdx86 code,
15 * this header provides a helper for getting the serdev-controller device.
16 */
17#include <linux/acpi.h>
18#include <linux/device.h>
19#include <linux/err.h>
20#include <linux/printk.h>
21#include <linux/sprintf.h>
22#include <linux/string.h>
23
24static inline struct device *
25get_serdev_controller(const char *serial_ctrl_hid,
26		      const char *serial_ctrl_uid,
27		      int serial_ctrl_port,
28		      const char *serdev_ctrl_name)
29{
30	struct device *ctrl_dev, *child;
31	struct acpi_device *ctrl_adev;
32	char name[32];
33	int i;
34
35	ctrl_adev = acpi_dev_get_first_match_dev(serial_ctrl_hid, serial_ctrl_uid, -1);
36	if (!ctrl_adev) {
37		pr_err("error could not get %s/%s serial-ctrl adev\n",
38		       serial_ctrl_hid, serial_ctrl_uid);
39		return ERR_PTR(-ENODEV);
40	}
41
42	/* get_first_physical_node() returns a weak ref */
43	ctrl_dev = get_device(acpi_get_first_physical_node(ctrl_adev));
44	if (!ctrl_dev) {
45		pr_err("error could not get %s/%s serial-ctrl physical node\n",
46		       serial_ctrl_hid, serial_ctrl_uid);
47		ctrl_dev = ERR_PTR(-ENODEV);
48		goto put_ctrl_adev;
49	}
50
51	/* Walk host -> uart-ctrl -> port -> serdev-ctrl */
52	for (i = 0; i < 3; i++) {
53		switch (i) {
54		case 0:
55			snprintf(name, sizeof(name), "%s:0", dev_name(ctrl_dev));
56			break;
57		case 1:
58			snprintf(name, sizeof(name), "%s.%d",
59				 dev_name(ctrl_dev), serial_ctrl_port);
60			break;
61		case 2:
62			strscpy(name, serdev_ctrl_name, sizeof(name));
63			break;
64		}
65
66		child = device_find_child_by_name(ctrl_dev, name);
67		put_device(ctrl_dev);
68		if (!child) {
69			pr_err("error could not find '%s' device\n", name);
70			ctrl_dev = ERR_PTR(-ENODEV);
71			goto put_ctrl_adev;
72		}
73
74		ctrl_dev = child;
75	}
76
77put_ctrl_adev:
78	acpi_dev_put(ctrl_adev);
79	return ctrl_dev;
80}
81