From: Hans de Goede hdegoede@redhat.com
[ Upstream commit 99b572e6136eab69a8c91d72cf8595b256e304b5 ]
Some recent(ish) Dell AIO devices have a backlight controller board connected to an UART.
This UART has a DELL0501 HID with CID set to PNP0501 so that the UART is still handled by 8250_pnp.c. Unfortunately there is no separate ACPI device with an UartSerialBusV2() resource to model the backlight-controller. This causes the kernel to create a /dev/ttyS0 char-device for the UART instead of creating an in kernel serdev-controller + serdev-device pair for a kernel backlight driver.
Use the existing acpi_quirk_skip_serdev_enumeration() mechanism to work around this by returning skip=true for tty-ctrl parents with a HID of DELL0501.
Like other cases where the UartSerialBusV2() resource is missing or broken this will only create the serdev-controller device and the serdev-device itself will need to be instantiated by platform code.
Unfortunately in this case there is no device for the platform-code instantiating the serdev-device to bind to. So also create a platform_device for this.
Signed-off-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/x86/utils.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/drivers/acpi/x86/utils.c b/drivers/acpi/x86/utils.c index 8829a907eee02..90c3d2eab9e99 100644 --- a/drivers/acpi/x86/utils.c +++ b/drivers/acpi/x86/utils.c @@ -484,8 +484,28 @@ static int acpi_dmi_skip_serdev_enumeration(struct device *controller_parent, bo
int acpi_quirk_skip_serdev_enumeration(struct device *controller_parent, bool *skip) { + struct acpi_device *adev = ACPI_COMPANION(controller_parent); + *skip = false;
+ /* + * The DELL0501 ACPI HID represents an UART (CID is set to PNP0501) with + * a backlight-controller attached. There is no separate ACPI device with + * an UartSerialBusV2() resource to model the backlight-controller. + * Set skip to true so that the tty core creates a serdev ctrl device. + * The backlight driver will manually create the serdev client device. + */ + if (acpi_dev_hid_match(adev, "DELL0501")) { + *skip = true; + /* + * Create a platform dev for dell-uart-backlight to bind to. + * This is a static device, so no need to store the result. + */ + platform_device_register_simple("dell-uart-backlight", PLATFORM_DEVID_NONE, + NULL, 0); + return 0; + } + return acpi_dmi_skip_serdev_enumeration(controller_parent, skip); } EXPORT_SYMBOL_GPL(acpi_quirk_skip_serdev_enumeration);