Re: [PATCH] Input: bcm5974 - report highest finger pressure to Synaptics

[Henrik Rydberg <rydberg@bitmath.org>]

On 06/03/2015 02:31 PM, Matt Whitlock wrote:
> On Wednesday, 3 June 2015, at 2:24 pm, Henrik Rydberg wrote:
>>> This patch changes the report_synaptics_data() function so that it reports
>>> the highest touch_major and highest tool_major of any touching finger as
>>> ABS_PRESSURE and ABS_TOOL_WIDTH, respectively.
>>
>> I appreciate the problem, but I would much rather have bcm5974 converted
>> to use input_mt_report_pointer_emulation() instead. The emulation code
>> has been left as is for a long while, but this seems to be a good time
>> to convert it.
> 
> report_tp_state() calls input_mt_sync_frame(), which in turn calls input_mt_report_pointer_emulation() already. So does this mean that report_synaptics_data() can be removed entirely?
> 

The bcm5974 driver does not advertise ABS_MT_PRESSURE, and therefore
ABS_PRESSURE is not reported via input_mt_sync_frame(). Furthermore,
ABS_TOOL_WIDTH is not handled at all in input_mt_report_pointer_emulation().

To handle pressure automatically, one would need to advertise (and use)
ABS_MT_PRESSURE. There is a misnomer in the driver, let say for historical
reasons, so that ABS_MT_TOUCH_MAJOR gets reported in the ABS_PRESSURE field.
This is a bit of a problem, but quite solvable.

For tool width, it is hard to imagine ever being able to remove that
functionality completely. However, it can be transferred to
input_mt_report_pointer_emulation() instead, provided every user of that
function is analyzed for consequences and usage of ABS_MT_WIDTH_MAJOR.

It would be great to simply remove report_synaptics_data(), if possible,
retaining the precise behavior. Barring the bug, of course.

Thanks,
Henrik