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SubjectRe: [PATCH v3 2/2] Input: xen-kbdfront - allow better run-time configuration
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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?
> Thanks.
>
Thank you,
Oleksandr

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