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Subject[PATCH v4 01/16] input: goldfish: Fix multitouch event handling
Date
From: Lingfeng Yang <lfy@google.com>

Register Goldfish Events device properly as a multitouch device,
and send SYN_REPORT events in appropriate cases only.

If SYN_REPORT event is sent on every single multitouch event, it
breaks the multitouch support. The multitouch interaction becomes
janky and user has to click 2-3 times to do stuff (also, notification
bars are randomly activating when not clicking). If these SYN_REPORT
events are suppressed, multitouch works fine, plus the events have a
protocol that looks nice.

In addition, Goldfish Events device needs to be registered as a
multitouch device by issuing input_mt_init_slots. Otherwise,
input_handle_abs_event in drivers/input/input.c will silently drop
all ABS_MT_SLOT events, causing touches with more than one finger
not to work properly.

Signed-off-by: Lingfeng Yang <lfy@google.com>
Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com>
Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com>
Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
---
drivers/input/keyboard/goldfish_events.c | 35 +++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/input/keyboard/goldfish_events.c b/drivers/input/keyboard/goldfish_events.c
index f6e643b..bc3e8b3 100644
--- a/drivers/input/keyboard/goldfish_events.c
+++ b/drivers/input/keyboard/goldfish_events.c
@@ -17,6 +17,7 @@
#include <linux/interrupt.h>
#include <linux/types.h>
#include <linux/input.h>
+#include <linux/input/mt.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
@@ -24,6 +25,8 @@
#include <linux/io.h>
#include <linux/acpi.h>

+#define GOLDFISH_MAX_FINGERS 5
+
enum {
REG_READ = 0x00,
REG_SET_PAGE = 0x00,
@@ -52,7 +55,22 @@ static irqreturn_t events_interrupt(int irq, void *dev_id)
value = __raw_readl(edev->addr + REG_READ);

input_event(edev->input, type, code, value);
- input_sync(edev->input);
+
+ /*
+ * Send an extra (EV_SYN, SYN_REPORT, 0x0) event only if a key
+ * was pressed. Some keyboard device drivers may only send the
+ * EV_KEY event and not the EV_SYN event.
+ *
+ * Note that sending an extra SYN_REPORT is not necessary nor
+ * correct protocol with other devices such as touchscreens,
+ * which will send their own SYN_REPORTs when sufficient event
+ * event information has been collected (for example, in case
+ * touchscreens, when pressure and X/Y coordinates have been
+ * received). Hence, we will only send this extra SYN_REPORT
+ * if type == EV_KEY.
+ */
+ if (type == EV_KEY)
+ input_sync(edev->input);
return IRQ_HANDLED;
}

@@ -155,6 +173,21 @@ static int events_probe(struct platform_device *pdev)
input_dev->name = edev->name;
input_dev->id.bustype = BUS_HOST;

+ /*
+ * Set the Goldfish Device to be multitouch.
+ *
+ * In the Ranchu kernel, there is multitouch-specific code for
+ * handling ABS_MT_SLOT events (see file drivers/input/input.c,
+ * function input_handle_abs_event). If we do not issue
+ * input_mt_init_slots, the kernel will filter out needed
+ * ABS_MT_SLOT events when we touch the screen in more than one
+ * place, preventing multitouch with more than one finger from
+ * working.
+ */
+ error = input_mt_init_slots(input_dev, GOLDFISH_MAX_FINGERS, 0);
+ if (error)
+ return error;
+
events_import_bits(edev, input_dev->evbit, EV_SYN, EV_MAX);
events_import_bits(edev, input_dev->keybit, EV_KEY, KEY_MAX);
events_import_bits(edev, input_dev->relbit, EV_REL, REL_MAX);
--
2.7.4
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