Re: [Xen-devel] [PATCH v3 2/2] Input: xen-kbdfront - allow better run-time configuration

[Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>]

Hi Oleksandr,

On Mon, May 14, 2018 at 05:40:29PM +0300, Oleksandr Andrushchenko wrote:
> @@ -211,93 +220,114 @@ static int xenkbd_probe(struct xenbus_device *dev,
>       if (!info->page)
>               goto error_nomem;
>  
> -     /* Set input abs params to match backend screen res */
> -     abs = xenbus_read_unsigned(dev->otherend,
> -                                XENKBD_FIELD_FEAT_ABS_POINTER, 0);
> -     ptr_size[KPARAM_X] = xenbus_read_unsigned(dev->otherend,
> -                                               XENKBD_FIELD_WIDTH,
> -                                               ptr_size[KPARAM_X]);
> -     ptr_size[KPARAM_Y] = xenbus_read_unsigned(dev->otherend,
> -                                               XENKBD_FIELD_HEIGHT,
> -                                               ptr_size[KPARAM_Y]);
> -     if (abs) {
> -             ret = xenbus_write(XBT_NIL, dev->nodename,
> -                                XENKBD_FIELD_REQ_ABS_POINTER, "1");
> -             if (ret) {
> -                     pr_warn("xenkbd: can't request abs-pointer\n");
> -                     abs = 0;
> -             }
> -     }
> +     /*
> +      * The below are reverse logic, e.g. if the feature is set, then
> +      * do not expose the corresponding virtual device.
> +      */
> +     with_kbd = !xenbus_read_unsigned(dev->nodename,
> +                                      XENKBD_FIELD_FEAT_DSBL_KEYBRD, 0);
>  
> -     touch = xenbus_read_unsigned(dev->nodename,
> -                                  XENKBD_FIELD_FEAT_MTOUCH, 0);
> -     if (touch) {
> +     with_ptr = !xenbus_read_unsigned(dev->nodename,
> +                                      XENKBD_FIELD_FEAT_DSBL_POINTER, 0);
> +
> +     /* Direct logic: if set, then create multi-touch device. */
> +     with_mtouch = xenbus_read_unsigned(dev->nodename,
> +                                        XENKBD_FIELD_FEAT_MTOUCH, 0);
> +     if (with_mtouch) {
>               ret = xenbus_write(XBT_NIL, dev->nodename,
>                                  XENKBD_FIELD_REQ_MTOUCH, "1");
>               if (ret) {
>                       pr_warn("xenkbd: can't request multi-touch");
> -                     touch = 0;
> +                     with_mtouch = 0;
>               }
>       }

Does it make sense to still end up calling xenkbd_connect_backend() when
all interfaces (keyboard, pointer, and multitouch) are disabled? Should
we do:

        if (!(with_kbd || || with_ptr || with_mtouch))
                return -ENXIO;

?

Thanks.

-- 
Dmitry

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