4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hans de Goede <hdego...@redhat.com>


[ 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 <hdego...@redhat.com>
Acked-by: Johan Hovold <jo...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/tty/serdev/core.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -54,6 +54,11 @@ static int serdev_uevent(struct device *
        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;


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