linux-kernel - Re: [PATCH 6/9 v4] Input: mt - document devices reporting more touches than slots

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Date:	Thu, 18 Aug 2011 09:01:39 -0700
From:	Chase Douglas <chase.douglas@...onical.com>
To:	Daniel Kurtz <djkurtz@...omium.org>
CC:	dmitry.torokhov@...il.com, rydberg@...omail.se,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	olofj@...omium.org, chris@...bagwell.com
Subject: Re: [PATCH 6/9 v4] Input: mt - document devices reporting more touches
 than slots

On 08/18/2011 04:28 AM, Daniel Kurtz wrote:
> Some devices are capable of identifying and/or tracking more contacts than
> they can report to the driver.  Document how a driver should handle this,
> and what userspace should expect.
> 
> Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
> ---
>  Documentation/input/multi-touch-protocol.txt |   14 ++++++++++++++
>  1 files changed, 14 insertions(+), 0 deletions(-)
> 
> diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt
> index 71536e7..543101c 100644
> --- a/Documentation/input/multi-touch-protocol.txt
> +++ b/Documentation/input/multi-touch-protocol.txt
> @@ -65,6 +65,20 @@ the full state of each initiated contact has to reside in the receiving
>  end.  Upon receiving an MT event, one simply updates the appropriate
>  attribute of the current slot.
>  
> +Some devices identify and/or track more contacts than they can report to the
> +driver.  A driver for such a device should associate one type B slot with each
> +contact that is reported by the hardware.  Whenever the identity of the
> +contact associated with a slot changes, the driver should invalidate that
> +slot by changing its ABS_MT_TRACKING_ID.  If the hardware signals that it is
> +tracking more contacts than it is currently reporting, the driver should use
> +a BTN_TOOL_*TAP event to inform userspace of the total number of contacts
> +being tracked by the hardware at that moment.  The driver should do this by
> +explicitly sending the corresponding BTN_TOOL_*TAP event and setting
> +use_count to false when calling input_mt_report_pointer_emulation().
> +The driver should only advertise as many slots as the hardware can report.
> +Userspace can detect that a driver can report more total contacts than slots
> +by noting that the largest supported BTN_TOOL_*TAP event is larger than the
> +total number of type B slots reported in the absinfo for the ABS_MT_SLOT axis.
>  
>  Protocol Example A
>  ------------------

Acked-by: Chase Douglas <chase.douglas@...onical.com>

Thanks a bunch Daniel!
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