Re: [PATCH 4/4] Input: Synaptics: Add INPUT_PROP_SYNAPTICS_T3R2 property

[Derek Foreman <derek@collabora.co.uk>]

On 06/10/11 17:13, Henrik Rydberg wrote:
> On Fri, Jun 10, 2011 at 03:55:04PM -0400, Derek Foreman wrote:
>> This new property indicates that the trackpad is able to track more than two contacts, but can only report the positions of two contacts due to bus bandwidth limitations.
>>
>> Signed-off-by: Derek Foreman<derek.foreman@collabora.co.uk>
>> ---
>>   drivers/input/mouse/synaptics.c |    3 +++
>>   include/linux/input.h           |    1 +
>>   2 files changed, 4 insertions(+), 0 deletions(-)
>
> This information is already contained in INPUT_PROP_SEMI_MT, together
> with the use of BTN_TRIPLETAP. Please check
> Documentation/input/event-codes.txt for further details.

I really sorry, but I don't understand how this provides the same 
information.

INPUT_PROP_SEMI_MT, at least according to input.h specifies that the 
device reports a rectangle only, and not accurate touch co-ordinates.

BTN_TOOL_TRIPLETAP indicates that there are 3 fingers on the pad.


My intent was to indicate to userspace that the device is reporting 
co-ordinates like certain synaptics devices do:

3 fingers are accurately tracked
2 fingers are accurately (not bounding box) reported

Further, all the idiosyncrasies of the synaptics method of reporting apply:
The device has 3 "slots" for tracking data, and once they are all 
filled, it reports slots 1 and 3.  If the slot 1 contact is lifted, 
slots 2 and 3 will report.  If a third finger is once again added to the 
pad, it will become the new slot 1.

INPUT_PROP_SEMI_MT is actually inaccurate for these devices, and in 
retrospect, the bounding box patch should have removed that bit from the 
properties of the devices it applies to.