[PATCH] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
DORMANTno replies
From: Colin Xu <hidden>
Date: 2021-01-08 03:42:34
Also in:
lkml
Subsystem:
the rest, virtio core, virtio input driver · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang, Eugenio Pérez, Gerd Hoffmann
In 'commit 29cc309d8bf1 ("HID: hid-multitouch: forward MSC_TIMESTAMP")',
EV_MSC/MSC_TIMESTAMP is added to each before EV_SYN event. EV_MSC is
configured as INPUT_PASS_TO_ALL.
In case of a touch device which report MSC_TIMESTAMP:
BE pass EV_MSC/MSC_TIMESTAMP to FE on receiving event from evdev.
FE pass EV_MSC/MSC_TIMESTAMP back to BE.
BE writes EV_MSC/MSC_TIMESTAMP to evdev due to INPUT_PASS_TO_ALL.
BE receives extra EV_MSC/MSC_TIMESTAMP and pass to FE.quoted
quoted
Each new frame becomes larger and larger.
Disable EV_MSC/MSC_TIMESTAMP forwarding for MT. Signed-off-by: Colin Xu <redacted> --- drivers/virtio/virtio_input.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
index f1f6208edcf5..244965c20d9b 100644
--- a/drivers/virtio/virtio_input.c
+++ b/drivers/virtio/virtio_input.c@@ -64,6 +64,21 @@ static int virtinput_send_status(struct virtio_input *vi, unsigned long flags; int rc; + /* + * Since 29cc309d8bf1 (HID: hid-multitouch: forward MSC_TIMESTAMP), + * EV_MSC/MSC_TIMESTAMP is added to each before EV_SYN event. + * EV_MSC is configured as INPUT_PASS_TO_ALL. + * In case of touch device: + * BE pass EV_MSC/MSC_TIMESTAMP to FE on receiving event from evdev. + * FE pass EV_MSC/MSC_TIMESTAMP back to BE. + * BE writes EV_MSC/MSC_TIMESTAMP to evdev due to INPUT_PASS_TO_ALL. + * BE receives extra EV_MSC/MSC_TIMESTAMP and pass to FE. + * >>> Each new frame becomes larger and larger. + * Disable EV_MSC/MSC_TIMESTAMP forwarding for MT. + */ + if (vi->idev->mt && type == EV_MSC && code == MSC_TIMESTAMP) + return 0; + stsbuf = kzalloc(sizeof(*stsbuf), GFP_ATOMIC); if (!stsbuf) return -ENOMEM;
--
2.30.0
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