drivers/platform/x86/serdev_helpers.h

   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 *
  25 get_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
  77 put_ctrl_adev:
  78         acpi_dev_put(ctrl_adev);
  79         return ctrl_dev;
  80 }