[PATCH v2 3/3] serdev: Do not instantiate serdevs on boards with known bogus DSDT entries

[Hans de Goede <hdegoede@redhat.com>]

x86 ACPI devices which ship with only Android as their factory image use
older kernels which do not yet support ACPI serdev enumeration, as such
the serdev information in their ACPI tables is not reliable.

For example on the Asus ME176C tablet the serdev describing the Bluetooth
HCI points to the serdev_controller connected to the GPS and the other way
around.

Use the new acpi_quirk_skip_serdev_enumeration() helper to identify
known boards with this issue and then either abort adding the serdev
controller (creating a tty cdev instead) or only create the controller
leaving the instantation of the serdev itself up to platform code.

In the case where only the serdev controller is created the necessary
serdevs will instead be instantiated by the
drivers/platform/x86/x86-android-tablets.c kernel module.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/tty/serdev/core.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index f1324fe99378..92e3433276f8 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -727,10 +727,24 @@ static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
 static int acpi_serdev_register_devices(struct serdev_controller *ctrl)
 {
 	acpi_status status;
+	bool skip;
+	int ret;
 
 	if (!has_acpi_companion(ctrl->dev.parent))
 		return -ENODEV;
 
+	/*
+	 * Skip registration on boards where the ACPI tables are known to
+	 * contain buggy devices. Note serdev_controller_add() must still
+	 * succeed in this case, so that the proper serdev devices can be
+	 * added "manually" later.
+	 */
+	ret = acpi_quirk_skip_serdev_enumeration(ctrl->dev.parent, &skip);
+	if (ret)
+		return ret;
+	if (skip)
+		return 0;
+
 	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
 				     SERDEV_ACPI_MAX_SCAN_DEPTH,
 				     acpi_serdev_add_device, NULL, ctrl, NULL);
-- 
2.33.1