[Fw_Os_Forum] How to detect devices that support touch

Venkat Gorla venkatagorla at gmail.com
Fri Mar 4 04:49:40 EST 2016

Thanks Aaron. Now when I get the list of handles, I am testing for the
device path protocol in addition to the absolute pointer protocol.

By doing so, I am able to filter out the negative scenarios.

I have another related question on this topic.

On some of the touch hardware on which we are testing our product changes,
when enumerating the handles, if we select the first handle that has both
absolute pointer protocol and device path protocol, it doesn't seem to
function always -- touch events aren't being received.

On the other hand, if we select the **last** handle that has both
protocols, it seems to work always.

So is there something about this first handle vs last handle that will
explain this behavior?


On Thu, Mar 3, 2016 at 11:38 PM, <Aaron.Pop at congatec.com> wrote:

> EDK implements a console splitter for input device.  This console splitter
> creates a absolute pointer protocol instance that does not contain a device
> path.
> You can locate a handle buffer of all the handles that contain an absolute
> pointer protocol, and then you can go through the handles and make sure
> that there is a handle that contains a device path.  If there are no
> absolute pointer instances that contain a device path.
> From:        Venkat Gorla <venkatagorla at gmail.com>
> To:        fw_os_forum at mailman.uefi.org,
> Date:        03/03/2016 01:06 AM
> Subject:        [Fw_Os_Forum] How to detect devices that support touch
> Sent by:        fw_os_forum-bounces at mailman.uefi.org
> ------------------------------
> Hello,
> We are making some product changes that are specific to touch devices
> (such as a tablet) in the Windows pre-boot UEFI environment. I am referring
> the following document for the UEFI specification:
> http://www.uefi.org/sites/default/files/resources/UEFI_Spec_2_3_1.pdf
> However I haven't been able to definitively check for touch devices vs
> non-touch devices using the specification.
> For example, querying for the absolute pointer protocol interface succeeds
> even on a non-touch device such as a laptop or a desktop. Additionally, the
> absolute max X and max Y values are also being reported as non-zero when I
> query the "Mode" of the protocol interface.
> So my question is how do I filter out the negative scenarios (devices that
> don't support touch) using the UEFI specification?
> Any pointers or help will is much appreciated.
> Thanks,
> Venkat _______________________________________________
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> Fw_os_forum at mailman.uefi.org
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