linux-kernel - [PATCH AUTOSEL 5.6 018/149] HID: lg-g15: Do not fail the probe when we fail to disable F# emulation

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Date:   Sat, 11 Apr 2020 19:01:35 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hans de Goede <hdegoede@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
        Sasha Levin <sashal@...nel.org>, linux-input@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 018/149] HID: lg-g15: Do not fail the probe when we fail to disable F# emulation

From: Hans de Goede <hdegoede@...hat.com>

[ Upstream commit b8a75eaddae9410767c7d95a1c5f3a547aae7b81 ]

By default the G1-G12 keys on the Logitech gaming keyboards send
F1 - F12 when in "generic HID" mode.

The first thing the hid-lg-g15 driver does is disable this behavior.

We have received a bugreport that this does not work when the keyboard
is connected through an Aten KVM switch. Using a gaming keyboard with
a KVM is a bit weird setup, but still we can try to fail a bit more
gracefully here.

On the G510 keyboards the same USB-interface which is used for the gaming
keys is also used for the media-keys. Before this commit we would call
hid_hw_stop() on failure to disable the F# emulation and then exit the
probe method with an error code.

This not only causes us to not handle the gaming-keys, but this also
breaks the media keys which is a regression compared to the situation
when these keyboards where handled by the generic hidinput driver.

This commit changes the error handling to clear the hiddev drvdata
(to disable our .raw_event handler) and then returning from the probe
method with success.

The net result of this is that, when connected through a KVM, things
work as well as they did before the hid-lg-g15 driver was introduced.

Fixes: ad4203f5a243 ("HID: lg-g15: Add support for the G510 keyboards' gaming keys")
BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1806321
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hid/hid-lg-g15.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-lg-g15.c b/drivers/hid/hid-lg-g15.c
index 8a9268a5c66aa..ad4b5412a9f49 100644
--- a/drivers/hid/hid-lg-g15.c
+++ b/drivers/hid/hid-lg-g15.c
@@ -803,8 +803,10 @@ static int lg_g15_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	}

 	if (ret < 0) {
-		hid_err(hdev, "Error disabling keyboard emulation for the G-keys\n");
-		goto error_hw_stop;
+		hid_err(hdev, "Error %d disabling keyboard emulation for the G-keys, falling back to generic hid-input driver\n",
+			ret);
+		hid_set_drvdata(hdev, NULL);
+		return 0;
 	}

 	/* Get initial brightness levels */
-- 
2.20.1