linux-kernel - [PATCH 2/8] Input: serio - add fast reconnect option

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Message-Id: <20170309221644.17035-3-dmitry.torokhov@gmail.com>
Date:   Thu,  9 Mar 2017 14:16:38 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: [PATCH 2/8] Input: serio - add fast reconnect option

Devices connected to serio bus are quite slow, and to improve apparent
speed of resume process, serio core resumes (reconnects) its devices
asynchronously, by posting port reconnect requests to a workqueue.
Unfortunately this means that if there is a dependent device of a given
serio port (for example SMBus part of touchpad connected via both PS/2 and
SMBus), we do not have a good way of ensuring resume order.

This change allows drivers to define "fast reconnect" handlers that would
be called in-line during system resume. Drivers need to ensure that these
handlers are truly "fast".

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/serio/serio.c | 22 +++++++++++++++++-----
 include/linux/serio.h       |  1 +
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/input/serio/serio.c b/drivers/input/serio/serio.c
index 1ca7f551e2da..34793ce2df91 100644
--- a/drivers/input/serio/serio.c
+++ b/drivers/input/serio/serio.c
@@ -953,12 +953,24 @@ static int serio_suspend(struct device *dev)
 static int serio_resume(struct device *dev)
 {
 	struct serio *serio = to_serio_port(dev);
+	int error = -ENOENT;
 
-	/*
-	 * Driver reconnect can take a while, so better let kseriod
-	 * deal with it.
-	 */
-	serio_queue_event(serio, NULL, SERIO_RECONNECT_PORT);
+	mutex_lock(&serio->drv_mutex);
+	if (serio->drv && serio->drv->fast_reconnect) {
+		error = serio->drv->fast_reconnect(serio);
+		if (error && error != -ENOENT)
+			dev_warn(dev, "fast reconnect failed with error %d\n",
+				 error);
+	}
+	mutex_unlock(&serio->drv_mutex);
+
+	if (error) {
+		/*
+		 * Driver reconnect can take a while, so better let
+		 * kseriod deal with it.
+		 */
+		serio_queue_event(serio, NULL, SERIO_RECONNECT_PORT);
+	}
 
 	return 0;
 }
diff --git a/include/linux/serio.h b/include/linux/serio.h
index c733cff44e18..138a5efe863a 100644
--- a/include/linux/serio.h
+++ b/include/linux/serio.h
@@ -77,6 +77,7 @@ struct serio_driver {
 	irqreturn_t (*interrupt)(struct serio *, unsigned char, unsigned int);
 	int  (*connect)(struct serio *, struct serio_driver *drv);
 	int  (*reconnect)(struct serio *);
+	int  (*fast_reconnect)(struct serio *);
 	void (*disconnect)(struct serio *);
 	void (*cleanup)(struct serio *);
 
-- 
2.12.0.246.ga2ecc84866-goog