Re: [PATCH RESEND v2] virtio-input: add multi-touch support

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Cc: virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
	stable@vger.kernel.org, Jason Wang <jasowang@redhat.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Henrik Rydberg <rydberg@bitmath.org>,
	Mathias Crombez <mathias.crombez@faurecia.com>
Subject: Re: [PATCH RESEND v2] virtio-input: add multi-touch support
Date: Wed, 9 Dec 2020 03:28:33 -0500	[thread overview]
Message-ID: <20201209030635-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201208210150.20001-1-vasyl.vavrychuk@opensynergy.com>

On Tue, Dec 08, 2020 at 11:01:50PM +0200, Vasyl Vavrychuk wrote:
> From: Mathias Crombez <mathias.crombez@faurecia.com>
> Cc: stable@vger.kernel.org

I don't believe this is appropriate for stable, looks like
a new feature to me.

> 
> Without multi-touch slots allocated, ABS_MT_SLOT events will be lost by
> input_handle_abs_event.
> 
> Signed-off-by: Mathias Crombez <mathias.crombez@faurecia.com>
> Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
> Tested-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
> ---
> v2: fix patch corrupted by corporate email server
> 
>  drivers/virtio/Kconfig        | 11 +++++++++++
>  drivers/virtio/virtio_input.c |  8 ++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
> index 7b41130d3f35..2cfd5b01d96d 100644
> --- a/drivers/virtio/Kconfig
> +++ b/drivers/virtio/Kconfig
> @@ -111,6 +111,17 @@ config VIRTIO_INPUT
>  
>  	 If unsure, say M.
>  
> +config VIRTIO_INPUT_MULTITOUCH_SLOTS
> +	depends on VIRTIO_INPUT
> +	int "Number of multitouch slots"
> +	range 0 64
> +	default 10
> +	help
> +	 Define the number of multitouch slots used. Default to 10.
> +	 This parameter is unused if there is no multitouch capability.
> +
> +	 0 will disable the feature.
> +

Most people won't be using this config so the defaults matter. So why 10? 10 fingers?

And where does 64 come from?

>  config VIRTIO_MMIO
>  	tristate "Platform bus driver for memory mapped virtio devices"
>  	depends on HAS_IOMEM && HAS_DMA
> diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
> index f1f6208edcf5..13f3d90e6c30 100644
> --- a/drivers/virtio/virtio_input.c
> +++ b/drivers/virtio/virtio_input.c
> @@ -7,6 +7,7 @@
>  
>  #include <uapi/linux/virtio_ids.h>
>  #include <uapi/linux/virtio_input.h>
> +#include <linux/input/mt.h>
>  
>  struct virtio_input {
>  	struct virtio_device       *vdev;
> @@ -205,6 +206,7 @@ static int virtinput_probe(struct virtio_device *vdev)
>  	unsigned long flags;
>  	size_t size;
>  	int abs, err;
> +	bool is_mt = false;
>  
>  	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
>  		return -ENODEV;
> @@ -287,9 +289,15 @@ static int virtinput_probe(struct virtio_device *vdev)
>  		for (abs = 0; abs < ABS_CNT; abs++) {
>  			if (!test_bit(abs, vi->idev->absbit))
>  				continue;
> +			if (input_is_mt_value(abs))
> +				is_mt = true;
>  			virtinput_cfg_abs(vi, abs);
>  		}
>  	}
> +	if (is_mt)
> +		input_mt_init_slots(vi->idev,
> +				    CONFIG_VIRTIO_INPUT_MULTITOUCH_SLOTS,
> +				    INPUT_MT_DIRECT);

Do we need the number in config space maybe? And maybe with a feature
bit so host can find out whether guest supports MT?

>  
>  	virtio_device_ready(vdev);
>  	vi->ready = true;
> -- 
> 2.23.0