From 42764f97e6ebf1ff518c83e4a36395fddf7a6085 Mon Sep 17 00:00:00 2001 From: Benjamin Tissoires Date: Thu, 3 Feb 2022 15:32:26 +0100 Subject: Input: docs: add more details on the use of BTN_TOOL The HID core stack used to be very relaxed considering the BTN_TOOL_* usage. With the recent commits, we should now enforce to have only one tool at a time, meaning that we can now express that requirement in the docs. Signed-off-by: Benjamin Tissoires Reviewed-by: Ping Cheng Acked-by: Peter Hutterer Signed-off-by: Jiri Kosina --- Documentation/input/event-codes.rst | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'Documentation/input') diff --git a/Documentation/input/event-codes.rst b/Documentation/input/event-codes.rst index b24ae7d292cc..8741d390b184 100644 --- a/Documentation/input/event-codes.rst +++ b/Documentation/input/event-codes.rst @@ -137,7 +137,11 @@ A few EV_KEY codes have special meanings: code should be set to a value of 1. When the tool is no longer interacting with the input device, the BTN_TOOL_ code should be reset to 0. All trackpads, tablets, and touchscreens should use at least one BTN_TOOL_ - code when events are generated. + code when events are generated. Likewise all trackpads, tablets, and + touchscreens should export only one BTN_TOOL_ at a time. To not break + existing userspace, it is recommended to not switch tool in one EV_SYN frame + but first emitting the old BTN_TOOL_ at 0, then emit one SYN_REPORT + and then set the new BTN_TOOL_ at 1. * BTN_TOUCH: -- cgit v1.2.3