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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
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.