[PATCH 6.8 037/143] ACPI: x86: Add DELL0501 handling to acpi_quirk_skip_serdev_enumeration()

Greg Kroah-Hartman
2024-04-11T10:08:28Z

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);
--
2.43.0