[PATCH AUTOSEL for 4.15 094/124] serdev: Fix serdev_uevent failure on ACPI enumerated serdev-controllers

[Sasha Levin]

From: Hans de Goede <hdegoede@xxxxxxxxxx>

[ Upstream commit 7d09995dcb0577b4a56aad7f2bb56f28604e8f1a ]

ACPI enumerated serdev-controllers do not have an ACPI companion, the ACPI
companion belongs to the serdev-device child of the serdev-controller, not
to the controller itself. This was causing serdev_uevent to always return
-ENODEV when called on a serdev-controller leading to errors like these:

kernel: serial serial0: uevent: failed to send synthetic uevent

being logged. This commit modifies serdev_uevent to directly return 0
when called on an ACPI enumerated serdev-controller fixing this.

Note: I do not think that setting a modalias on a devicetree enumerated
serdev-controller makes sense either. So perhaps the !dev->of_node part of
the check can be dropped too, but I'm not entirely sure that doing this
on devicetree too is correct.

Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Acked-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 drivers/tty/serdev/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 1bef39828ca7..571ce1f69d8d 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -54,6 +54,11 @@ static int serdev_uevent(struct device *dev, struct kobj_uevent_env *env)
 	int rc;
 
 	/* TODO: platform modalias */
+
+	/* ACPI enumerated controllers do not have a modalias */
+	if (!dev->of_node && dev->type == &serdev_ctrl_type)
+		return 0;
+
 	rc = acpi_device_uevent_modalias(dev, env);
 	if (rc != -ENODEV)
 		return rc;
-- 
2.14.1