From: Colin Xu <colin.xu@intel.com>
To: kraxel@redhat.com, mst@redhat.com, jasowang@redhat.com
Cc: virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, colin.xu@intel.com
Subject: [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT.
Date: Tue, 2 Feb 2021 08:19:23 +0800 [thread overview]
Message-ID: <20210202001923.6227-1-colin.xu@intel.com> (raw)
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
next reply other threads:[~2021-02-02 0:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-02 0:19 Colin Xu [this message]
2021-02-03 14:25 ` [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm for MT Gerd Hoffmann
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