Colin Xu
2021-Jan-08 03:41 UTC
[PATCH] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
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.>>> Each new frame becomes larger and larger.Disable EV_MSC/MSC_TIMESTAMP forwarding for MT. Signed-off-by: Colin Xu <colin.xu at intel.com> --- 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