kernel/drivers/platform/x86/serdev_helpers.h, branch linux-6.9.yHosts the 0x221E linux distro kernel.https://universe.0xinfinity.dev/distro/kernel/atom?h=linux-6.9.y2024-02-20T13:35:35Zplatform/x86: Add new get_serdev_controller() helper2024-02-20T13:35:35ZHans de Goedehdegoede@redhat.com2024-02-16T20:17:19Zurn:sha1:dc5afd720f84de3c1f5d700eb0b858006a2dc468
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
commit b286f4e87e32 ("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: b286f4e87e32 ("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