Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Jiri Kosina <jikos@kernel.org>, Bastien Nocera <hadess@hadess.net>
Cc:     Filipe =?ISO-8859-1?Q?La=EDns?= <lains@riseup.net>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        linux-input@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Thorsten Leemhuis <regressions@leemhuis.info>
Subject: [PATCH v1 1/2] HID: generic: Add ->match() check to __check_hid_generic()
Date:   Wed, 07 Dec 2022 10:11:50 +0100
Message-ID: <4809717.31r3eYUQgx@kreacher>
In-Reply-To: <5647715.DvuYhMxLoT@kreacher>
References: <2262737.ElGaqSPkdT@kreacher> <5647715.DvuYhMxLoT@kreacher>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Some special HID drivers (for example, hid-logitech-hidpp) use ->match()
callbacks to reject specific devices that otherwise would match the
driver's device ID list, with the expectation that those devices will
be handled by some other drivers.  However, this doesn't work if
hid-generic is expected to bind to the given device, because its
->match() callback, hid_generic_match(), rejects all devices that match
device ID lists of the other HID drivers regardless of what is returned
by the other drivers' ->match() callbacks.

To make it work, amend the function used by hid_generic_match() for
checking an individual driver, __check_hid_generic(), with a check
involving the given driver's ->match() callback, so 0 is returned
when that callback rejects the device in question.

Fixes: 532223c8ac57 ("HID: logitech-hidpp: Enable HID++ for all the Logitech Bluetooth devices")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/hid/hid-generic.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/hid/hid-generic.c
===================================================================
--- linux-pm.orig/drivers/hid/hid-generic.c
+++ linux-pm/drivers/hid/hid-generic.c
@@ -31,7 +31,13 @@ static int __check_hid_generic(struct de
 	if (hdrv == &hid_generic)
 		return 0;
 
-	return hid_match_device(hdev, hdrv) != NULL;
+	if (!hid_match_device(hdev, hdrv))
+		return 0;
+
+	if (hdrv->match)
+		return hdrv->match(hdev, false);
+
+	return 1;
 }
 
 static bool hid_generic_match(struct hid_device *hdev,