Input sync flag when registering.

Hi,
I noticed that with touchscreen drivers that don't explicitly call a input_sync after input_register_device, suspend to ram is blocked if no event is sent, because the input_dev created is considered as not synchronized. The problem was seen with Atmel mxt driver. When any event is sent, the driver explicitly ask a sync, so the problem is solved. The problem occurs only when the screen has never send any event before suspend to ram.
I solved it setting the sync element to true (when input dev is created, no element is pending).
Is there a better way to solve the problem ?
Thanks.
Thomas.

From: Thomas Poussevin <[email protected]>
Date: Fri, 22 Aug 2014 17:56:17 +0200
Subject: [PATCH] [input] Set input sync param default status to true, to
prevent touchscreen suspend fails. Problems used to happen only when touchsreen had not been touched since boot. When the first event is sent, input status is actualized.

---
 drivers/input/input.c | 1 +
 1 file changed, 1 insertion(+)

index 8921c61..c214b39 100644
@@ -1652,6 +1652,7 @@ struct input_dev *input_allocate_device(void)
 	if (dev) {
 		dev->dev.type = &input_dev_type;
 		dev->dev.class = &input_class;
+		dev->sync = true;
 		device_initialize(&dev->dev);
 		mutex_init(&dev->mutex);
 		spin_lock_init(&dev->event_lock);

1.9.2

Hi Thomas,

It is not clear to me what the problem is. The kernel as far as I remember never checked state of 'sync' field when executing suspend callbacks. Moreover there is no longer 'sync' field at all in mainline.

It sounds like some userspace code makes assumptions that are not always valid.

Thanks.

Dmitry

Indeed, there is no longer 'sync' field in mainline. I realized i missed some commits, specifically "Input: Send events one packet at a time" one.

Before theses commits, there used to be this problem, that is not relevant anymore :
It happened when Atmel mxt driver goes to suspend. mxt_stop func send a "input_sync" to mxt input device.
A input_sync has never been send before in input events.
The input_sync consists in : input_event(dev, EV_SYN, SYN_REPORT, 0);
In input_handle_event, if (!dev->sync) , then dev->sync = true; disposition = INPUT_PASS_TO_HANDLERS; . So finally there is a call to input_pass_event(dev, type, code, value); But the input device created by mxt driver is allready suspending.
Suspend is canceled.

So i have 2 solutions (other than kernel update): either, in mxt driver, sending a input_sync after creating input device in order than the suspend sync call is not the first one (dev->sync will be true next time). Either, in the input driver, the default value of sync field is true (coherent with a just created device). I choosed this one.

Thanks.
Thomas.

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