Re: [PATCH 2/4] platform/x86: Add new get_serdev_controller() helper

[Andy Shevchenko <andy@kernel.org>]

On Fri, Feb 16, 2024 at 09:17:19PM +0100, Hans de Goede wrote:
> 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.

The above doesn't explain why the new code is h-file.

...

> +#include <linux/acpi.h>

+ err.h

> +#include <linux/device.h>
> +#include <linux/printk.h>

+ sprintf.h
+ string.h

-- 
With Best Regards,
Andy Shevchenko