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

[Dmitry Torokhov]

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.torok...@gmail.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