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

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

On 05/17/2018 12:08 AM, Dmitry Torokhov wrote:
> On Wed, May 16, 2018 at 08:47:30PM +0300, Oleksandr Andrushchenko wrote:
> > On 05/16/2018 08:15 PM, Dmitry Torokhov wrote:
> > > 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;
> > >
> > > ?
> > It does make sense. Then we probably need to move all xenbus_read_unsigned
> > calls to the very beginning of the .probe, so no memory allocations are made
> > which will be useless if we return -ENXIO, e.g. something like
> >
> > static int xenkbd_probe(struct xenbus_device *dev,
> >                    const struct xenbus_device_id *id)
> > {
> >      int ret, i;
> >      bool with_mtouch, with_kbd, with_ptr;
> >      struct xenkbd_info *info;
> >      struct input_dev *kbd, *ptr, *mtouch;
> >
> > <read with_mtouch, with_kbd, with_ptr here>
> >
> > if (!(with_kbd | with_ptr | with_mtouch))
> >          return -ENXIO;
> >
> > Does the above looks ok?
> Yes. Another option is to keep the check where I suggested and do
>
>         if (...) {
>                 ret = -ENXIO;
>                 goto error;
>         }
>
> Whichever you prefer is fine with me.
I will go with the change you suggested and
I'll send v4 tomorrow then.
> Thanks.
Thank you,
Oleksandr

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