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authorBenjamin Tissoires <benjamin.tissoires@redhat.com>2022-02-03 15:32:26 +0100
committerJiri Kosina <jkosina@suse.cz>2022-03-01 15:46:03 +0100
commit42764f97e6ebf1ff518c83e4a36395fddf7a6085 (patch)
tree5acb6267b649b390af18c89979532166cf8283b0 /Documentation/input
parent5c20000a4756f57c824e3045c978ef19136a676d (diff)
downloadlinux-42764f97e6ebf1ff518c83e4a36395fddf7a6085.tar.bz2
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 <benjamin.tissoires@redhat.com> Reviewed-by: Ping Cheng <ping.cheng@wacom.com> Acked-by: Peter Hutterer <peter.hutterer@who-t.net> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'Documentation/input')
-rw-r--r--Documentation/input/event-codes.rst6
1 files changed, 5 insertions, 1 deletions
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_<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.
+ code when events are generated. Likewise all trackpads, tablets, and
+ touchscreens should export only one BTN_TOOL_<name> 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_<name> at 0, then emit one SYN_REPORT
+ and then set the new BTN_TOOL_<name> at 1.
* BTN_TOUCH: