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In some cases UART attached devices which require an in kernel driver, e.g. UART attached Bluetooth HCIs are described in the ACPI tables by an ACPI device with a broken or missing UartSerialBusV2() resource. This causes the kernel to create a /dev/ttyS# char-device for the UART instead of creating an in kernel serdev-controller + serdev-device pair for the in kernel driver. The quirk handling in acpi_quirk_skip_serdev_enumeration() makes the kernel create a serdev-controller device for these UARTs instead of a /dev/ttyS#. Instantiating the actual serdev-device to bind to is up to pdx86 code, so far this was handled by the x86-android-tablets code. But since commitb286f4e87e("serial: core: Move tty and serdev to be children of serial core port device") the serdev-controller device has moved in the device hierarchy from (e.g.) /sys/devices/pci0000:00/8086228A:00/serial0 to /sys/devices/pci0000:00/8086228A:00/8086228A:00:0/8086228A:00:0.0/serial0 . This makes this a bit trickier to do and another driver is in the works which will also need this functionality. Add a new helper to get the serdev-controller device, so that the new code for this can be shared. Fixes:b286f4e87e("serial: core: Move tty and serdev to be children of serial core port device") Cc: Tony Lindgren <tony@atomide.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Link: https://lore.kernel.org/r/20240216201721.239791-3-hdegoede@redhat.com
81 lines
2.3 KiB
C
81 lines
2.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* In some cases UART attached devices which require an in kernel driver,
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* e.g. UART attached Bluetooth HCIs are described in the ACPI tables
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* by an ACPI device with a broken or missing UartSerialBusV2() resource.
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*
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* This causes the kernel to create a /dev/ttyS# char-device for the UART
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* instead of creating an in kernel serdev-controller + serdev-device pair
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* for the in kernel driver.
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*
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* The quirk handling in acpi_quirk_skip_serdev_enumeration() makes the kernel
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* create a serdev-controller device for these UARTs instead of a /dev/ttyS#.
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*
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* Instantiating the actual serdev-device to bind to is up to pdx86 code,
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* this header provides a helper for getting the serdev-controller device.
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*/
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#include <linux/acpi.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/printk.h>
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#include <linux/sprintf.h>
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#include <linux/string.h>
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static inline struct device *
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get_serdev_controller(const char *serial_ctrl_hid,
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const char *serial_ctrl_uid,
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int serial_ctrl_port,
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const char *serdev_ctrl_name)
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{
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struct device *ctrl_dev, *child;
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struct acpi_device *ctrl_adev;
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char name[32];
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int i;
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ctrl_adev = acpi_dev_get_first_match_dev(serial_ctrl_hid, serial_ctrl_uid, -1);
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if (!ctrl_adev) {
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pr_err("error could not get %s/%s serial-ctrl adev\n",
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serial_ctrl_hid, serial_ctrl_uid);
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return ERR_PTR(-ENODEV);
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}
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/* get_first_physical_node() returns a weak ref */
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ctrl_dev = get_device(acpi_get_first_physical_node(ctrl_adev));
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if (!ctrl_dev) {
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pr_err("error could not get %s/%s serial-ctrl physical node\n",
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serial_ctrl_hid, serial_ctrl_uid);
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ctrl_dev = ERR_PTR(-ENODEV);
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goto put_ctrl_adev;
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}
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/* Walk host -> uart-ctrl -> port -> serdev-ctrl */
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for (i = 0; i < 3; i++) {
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switch (i) {
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case 0:
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snprintf(name, sizeof(name), "%s:0", dev_name(ctrl_dev));
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break;
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case 1:
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snprintf(name, sizeof(name), "%s.%d",
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dev_name(ctrl_dev), serial_ctrl_port);
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break;
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case 2:
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strscpy(name, serdev_ctrl_name, sizeof(name));
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break;
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}
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child = device_find_child_by_name(ctrl_dev, name);
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put_device(ctrl_dev);
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if (!child) {
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pr_err("error could not find '%s' device\n", name);
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ctrl_dev = ERR_PTR(-ENODEV);
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goto put_ctrl_adev;
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}
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ctrl_dev = child;
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}
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put_ctrl_adev:
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acpi_dev_put(ctrl_adev);
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return ctrl_dev;
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}
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