linux-kernel - Re: [PATCH V2] virtio_input: Prevent EV_MSC/MSC

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Date:   Wed, 3 Feb 2021 15:25:16 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Colin Xu <colin.xu@...el.com>
Cc:     mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] virtio_input: Prevent EV_MSC/MSC_TIMESTAMP loop storm
 for MT.

  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@...hat.com>

take care,
  Gerd