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
24 static inline struct device *
get_serdev_controller_from_parent(struct device * ctrl_dev,int serial_ctrl_port,const char * serdev_ctrl_name)25 get_serdev_controller_from_parent(struct device *ctrl_dev,
26 int serial_ctrl_port,
27 const char *serdev_ctrl_name)
28 {
29 struct device *child;
30 char name[32];
31 int i;
32
33 /* Walk host -> uart-ctrl -> port -> serdev-ctrl */
34 for (i = 0; i < 3; i++) {
35 switch (i) {
36 case 0:
37 snprintf(name, sizeof(name), "%s:0", dev_name(ctrl_dev));
38 break;
39 case 1:
40 snprintf(name, sizeof(name), "%s.%d",
41 dev_name(ctrl_dev), serial_ctrl_port);
42 break;
43 case 2:
44 strscpy(name, serdev_ctrl_name, sizeof(name));
45 break;
46 }
47
48 child = device_find_child_by_name(ctrl_dev, name);
49 put_device(ctrl_dev);
50 if (!child) {
51 pr_err("error could not find '%s' device\n", name);
52 return ERR_PTR(-ENODEV);
53 }
54
55 ctrl_dev = child;
56 }
57
58 return ctrl_dev;
59 }
60
61 static inline struct device *
get_serdev_controller(const char * serial_ctrl_hid,const char * serial_ctrl_uid,int serial_ctrl_port,const char * serdev_ctrl_name)62 get_serdev_controller(const char *serial_ctrl_hid,
63 const char *serial_ctrl_uid,
64 int serial_ctrl_port,
65 const char *serdev_ctrl_name)
66 {
67 struct acpi_device *adev;
68 struct device *parent;
69
70 adev = acpi_dev_get_first_match_dev(serial_ctrl_hid, serial_ctrl_uid, -1);
71 if (!adev) {
72 pr_err("error could not get %s/%s serial-ctrl adev\n",
73 serial_ctrl_hid, serial_ctrl_uid ?: "*");
74 return ERR_PTR(-ENODEV);
75 }
76
77 /* get_first_physical_node() returns a weak ref */
78 parent = get_device(acpi_get_first_physical_node(adev));
79 acpi_dev_put(adev);
80 if (!parent) {
81 pr_err("error could not get %s/%s serial-ctrl physical node\n",
82 serial_ctrl_hid, serial_ctrl_uid ?: "*");
83 return ERR_PTR(-ENODEV);
84 }
85
86 /* This puts our reference on parent and returns a ref on the ctrl */
87 return get_serdev_controller_from_parent(parent, serial_ctrl_port, serdev_ctrl_name);
88 }
89