Re: [PATCH v2] Documentation: Add evdev type and code definitions

[Nikolai Kondrashov <spbnick@gmail.com>]

On 01/08/2011 12:28 AM, Chase Douglas wrote:
> +* BTN_TOOL_<name>:
> +  - These codes are used in conjunction with input trackpads, tablets, and
> +    touchscreens. These devices may be used with fingers, pens, or other tools.
> +    When an event occurs and a tool is used, the corresponding BTN_TOOL_<name>
> +    code should be set to a value of 1. When the tool is no longer interacting
> +    with the input device, the BTN_TOOL_<name>  code should be reset to 0. All
> +    trackpads, tablets, and touchscreens should use at least one BTN_TOOL_<name>
> +    code when events are generated.

There are some tablets (namely UC-Logic ones), which do not indicate tool
proximity. Yet they may have both a pen and a mouse. They just send reports
with separate report IDs. Currently it is solved by using
HID_QUIRK_MULTI_INPUT and not sending any BTN_TOOL_* events.

Should the documentation reflect the fact that some tablets do not send any
BTN_TOOL_* events, or should the drivers be updated to synthesise them?

Note that in the latter case there will never be a BTN_TOOL_* with
zero value when the tool leaves the digitizing area, but only when the tools
are switched (if ever).

Sincerely,
Nick