* [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
@ 2021-02-02 0:19 Colin Xu
2021-02-03 14:25 ` Gerd Hoffmann
0 siblings, 1 reply; 2+ messages in thread
From: Colin Xu @ 2021-02-02 0:19 UTC (permalink / raw)
To: kraxel, mst, jasowang; +Cc: virtualization, linux-kernel, colin.xu
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.
V2: Rebase.
Signed-off-by: Colin Xu <colin.xu@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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
2021-02-02 0:19 [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT Colin Xu
@ 2021-02-03 14:25 ` Gerd Hoffmann
0 siblings, 0 replies; 2+ messages in thread
From: Gerd Hoffmann @ 2021-02-03 14:25 UTC (permalink / raw)
To: Colin Xu; +Cc: mst, jasowang, virtualization, linux-kernel
Hi,
> + /*
> + * 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;
> +
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
take care,
Gerd
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2021-02-03 14:26 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-02-02 0:19 [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT Colin Xu
2021-02-03 14:25 ` Gerd Hoffmann
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).