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From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
To: "Jiri Kosina" <jikos@kernel.org>,
	"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Ahelenia Ziemiańska" <nabijaczleweli@nabijaczleweli.xyz>,
	"Ping Cheng" <pinglinux@gmail.com>,
	"Aaron Armstrong Skomra" <skomra@gmail.com>,
	"Jason Gerecke" <killertofu@gmail.com>,
	"Peter Hutterer" <peter.hutterer@who-t.net>
Cc: linux-input@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>
Subject: [PATCH v2 12/12] Input: docs: add more details on the use of BTN_TOOL
Date: Thu,  3 Feb 2022 15:32:26 +0100	[thread overview]
Message-ID: <20220203143226.4023622-13-benjamin.tissoires@redhat.com> (raw)
In-Reply-To: <20220203143226.4023622-1-benjamin.tissoires@redhat.com>

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>

---

changes in v2:
- changed to explain that switching tool in one EV_SYN report
  is not nice for userspace
---
 Documentation/input/event-codes.rst | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

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:
 
-- 
2.33.1


  parent reply	other threads:[~2022-02-03 14:36 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-03 14:32 [PATCH v2 00/12] HID: fix for generic input processing Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 01/12] HID: core: statically allocate read buffers Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 02/12] HID: core: de-duplicate some code in hid_input_field() Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 03/12] HID: core: split data fetching from processing " Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 04/12] HID: input: tag touchscreens as such if the physical is not there Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 05/12] HID: input: rework spaghetti code with switch statements Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 06/12] HID: input: move up out-of-range processing of input values Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 07/12] HID: compute an ordered list of input fields to process Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 08/12] HID: core: for input reports, process the usages by priority list Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 09/12] HID: input: enforce Invert usage to be processed before InRange Benjamin Tissoires
2022-02-03 14:32 ` [PATCH v2 10/12] HID: input: remove the need for HID_QUIRK_INVERT Benjamin Tissoires
2022-02-04  1:41   ` Ping Cheng
2022-02-10  5:21   ` Ping Cheng
2022-02-10  5:43     ` Ping Cheng
2022-02-14 10:23       ` Benjamin Tissoires
2022-02-15  2:04         ` Ping Cheng
2022-02-15  8:51           ` Benjamin Tissoires
2022-02-16 12:42             ` Benjamin Tissoires
2022-02-17  1:27               ` Ping Cheng
2022-02-03 14:32 ` [PATCH v2 11/12] HID: input: accommodate priorities for slotted devices Benjamin Tissoires
2022-02-03 14:32 ` Benjamin Tissoires [this message]
2022-02-16  5:40   ` [PATCH v2 12/12] Input: docs: add more details on the use of BTN_TOOL Peter Hutterer
2022-03-01 14:53 ` [PATCH v2 00/12] HID: fix for generic input processing Jiri Kosina

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