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virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT. 

In 'commit 29cc309d8b ("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.

V2: Rebase.

Signed-off-by: Colin Xu <colin.xu@intel.com>
Link: https://lore.kernel.org/r/20210202001923.6227-1-colin.xu@intel.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Colin Xu 2021-02-02 08:19:23 +08:00 committed by Michael S. Tsirkin
parent d1e9aa9c34
commit a6829c350e
1 changed files with 15 additions and 0 deletions
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15
drivers/virtio/virtio_input.c
View File

@ -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;