Without multi-touch slots allocated, ABS_MT_SLOT events will be lost by
input_handle_abs_event.

Signed-off-by: Mathias Crombez <redacted>
Signed-off-by: Vasyl Vavrychuk <redacted>
Tested-by: Vasyl Vavrychuk <redacted>
---
v2: fix patch corrupted by corporate email server

 drivers/virtio/Kconfig        | 11 +++++++++++
 drivers/virtio/virtio_input.c |  8 ++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 7b41130d3f35..2cfd5b01d96d 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig

@@ -111,6 +111,17 @@ config VIRTIO_INPUT
 
 	 If unsure, say M.
 
+config VIRTIO_INPUT_MULTITOUCH_SLOTS
+	depends on VIRTIO_INPUT
+	int "Number of multitouch slots"
+	range 0 64
+	default 10
+	help
+	 Define the number of multitouch slots used. Default to 10.
+	 This parameter is unused if there is no multitouch capability.
+
+	 0 will disable the feature.
+

 config VIRTIO_MMIO
 	tristate "Platform bus driver for memory mapped virtio devices"
 	depends on HAS_IOMEM && HAS_DMA

diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
index f1f6208edcf5..13f3d90e6c30 100644
--- a/drivers/virtio/virtio_input.c
+++ b/drivers/virtio/virtio_input.c

@@ -7,6 +7,7 @@
 
 #include <uapi/linux/virtio_ids.h>
 #include <uapi/linux/virtio_input.h>
+#include <linux/input/mt.h>
 
 struct virtio_input {
 	struct virtio_device       *vdev;

@@ -205,6 +206,7 @@ static int virtinput_probe(struct virtio_device *vdev)
 	unsigned long flags;
 	size_t size;
 	int abs, err;
+	bool is_mt = false;
 
 	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
 		return -ENODEV;

@@ -287,9 +289,15 @@ static int virtinput_probe(struct virtio_device *vdev)
 		for (abs = 0; abs < ABS_CNT; abs++) {
 			if (!test_bit(abs, vi->idev->absbit))
 				continue;
+			if (input_is_mt_value(abs))
+				is_mt = true;
 			virtinput_cfg_abs(vi, abs);
 		}
 	}
+	if (is_mt)
+		input_mt_init_slots(vi->idev,
+				    CONFIG_VIRTIO_INPUT_MULTITOUCH_SLOTS,
+				    INPUT_MT_DIRECT);