Re: [PATCH] kbdif.h: Introduce feature-vkbd-standalone

[Oleksandr Andrushchenko <andr2000@gmail.com>]

Hi, Owen!

On 06/08/2017 04:09 PM, Owen Smith wrote:
> Backends set "feature-vkbd-standalone" to 1 if they can connect
> without waiting for the PV framebuffer. If this value is missing
> or not 1, then a backend will wait for the PV framebuffer before
> connecting, potentially causing the frontend to wait indefinitely.
This means that by the new option we *fix an existing
backend* and its particular behavior. What is more,
we introduce knowledge of virtual fb into generic virtual
kbd/ptr protocol which seems to be not correct (IMO).
For the reasons above, I would recommend fixing the
corresponding backend instead, for example by configuring
it appropriately wrt use-case you have.
> Frontends set "request-vkbd-standalone" to 1 to request that the
> backend does not wait for the PV framebuffer. Frontends that
> require a standalone vkbd device should not attempt to connect
> unless the backend advertises "feature-vkbd-standalone", and
> should set "request-vkbd-standalone".
Again, this looks very use-case specific
> Backends that are standalone (i.e. do not have an associated PV
> framebuffer) do not rescale absolute mouse or touch coordinates
> to a the size of the (non-existant) PV framebuffer, and use the
> range of [0, 0x7fff] for absolute values.
>
> Signed-off-by: Owen Smith <owen.smith@citrix.com>
> ---
>   xen/include/public/io/kbdif.h | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
>
> diff --git a/xen/include/public/io/kbdif.h b/xen/include/public/io/kbdif.h
> index dcbd71a..ca09080 100644
> --- a/xen/include/public/io/kbdif.h
> +++ b/xen/include/public/io/kbdif.h
> @@ -63,6 +63,12 @@
>    *      Backends, which support reporting of multi-touch events
>    *      should set this to 1.
>    *
> + * feature-vkbd-standalone
> + *      Values:         <uint>
> + *
> + *      Backends, which support a standalone vkbd, without requiring a vfb
> + *      device, should set this to 1.
> + *
>    *------------------------- Pointer Device Parameters ------------------------
>    *
>    * width
> @@ -98,6 +104,13 @@
>    *
>    *      Request backend to report multi-touch events.
>    *
> + * request-vkbd-standalone
> + *      Values:         <uint>
> + *
> + *      Request backend to connect vkbd device without waiting for the
> + *      vfb device. Any absolute coordinates will NOT be scaled to
> + *      screen size, and will remain in the range [0, 0x7fff]
> + *
>    *----------------------- Request Transport Parameters -----------------------
>    *
>    * event-channel
> @@ -165,8 +178,10 @@
>   
>   #define XENKBD_FIELD_FEAT_ABS_POINTER  "feature-abs-pointer"
>   #define XENKBD_FIELD_FEAT_MTOUCH       "feature-multi-touch"
> +#define XENKBD_FIELD_FEAT_STANDALONE   "feature-vkbd-standalone"
>   #define XENKBD_FIELD_REQ_ABS_POINTER   "request-abs-pointer"
>   #define XENKBD_FIELD_REQ_MTOUCH        "request-multi-touch"
> +#define XENKBD_FIELD_REQ_STANDALONE    "request-vkbd-standalone"
>   #define XENKBD_FIELD_RING_GREF         "page-gref"
>   #define XENKBD_FIELD_EVT_CHANNEL       "event-channel"
>   #define XENKBD_FIELD_WIDTH             "width"
Thank you,
Oleksandr

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