linux-kernel - [PATCH] HID: rmi: fallback to generic/multitouch if hid-rmi is not built (was Re: [GIT PULL] HID for 4.11)

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Date:   Tue, 21 Feb 2017 15:17:45 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Duggan <aduggan@...aptics.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org
Subject: [PATCH] HID: rmi: fallback to generic/multitouch if hid-rmi is not
 built (was Re: [GIT PULL] HID for 4.11)

On Mon, 20 Feb 2017, Linus Torvalds wrote:

> > I'll have a more specific commit (or range) soon.
> 
> Hmm. It's commit 279967a65b32 ("HID: rmi: Handle all Synaptics
> touchpads using hid-rmi").
> 
> And the reason seems to be stupid: I don't have RMI enabled at all,
> because that didn't use to work or make a difference.
> 
> Maybe that "let's use RMI" code should depend on RMI actually being
> enabled? Because as-is, that code now breaks existing configurations.

I agree; that's in line with what we usually try to stick to (force 
specific drivers if the device doesn't work with the generic at all and 
switch over to generic in compile-time for devices that have limited 
functionality with the generic driver).

Andrew, Benjamin, how about the patch below?




From: Jiri Kosina <jkosina@...e.cz>
Subject: [PATCH] HID: rmi: fallback to generic/multitouch if hid-rmi is not built

Commit 279967a65b32 ("HID: rmi: Handle all Synaptics touchpads using hid-rmi")
unconditionally switches over handling of all Synaptics touchpads to hid-rmi
(to make use of extended features of the HW); in case CONFIG_HID_RMI is
disabled though this renders the touchpad unusable, as the

	HID_DEVICE(HID_BUS_ANY, HID_GROUP_RMI, HID_ANY_ID, HID_ANY_ID)

match doesn't exist and generic/multitouch doesn't bind to it either (due
to hid group mismatch).

Fix this by switching over to hid-rmi only if it has been actually built.

Fixes: 279967a65b32 ("HID: rmi: Handle all Synaptics touchpads using hid-rmi")
Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
---
 drivers/hid/hid-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 538ff697a4cf..e9e87d337446 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -827,7 +827,8 @@ static int hid_scan_report(struct hid_device *hid)
 				 * hid-rmi should take care of them,
 				 * not hid-generic
 				 */
-				hid->group = HID_GROUP_RMI;
+				if (IS_ENABLED(CONFIG_HID_RMI))
+					hid->group = HID_GROUP_RMI;
 		break;
 	}
 

-- 
Jiri Kosina
SUSE Labs