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Jason Gerecke b43f977dd2 Revert "HID: wacom: generic: read the number of expected touches on a per collection basis" 
This reverts commit 15893fa401.

The referenced commit broke pen and touch input for a variety of devices
such as the Cintiq Pro 32. Affected devices may appear to work normally
for a short amount of time, but eventually loose track of actual touch
state and can leave touch arbitration enabled which prevents the pen
from working. The commit is not itself required for any currently-available
Bluetooth device, and so we revert it to correct the behavior of broken
devices.

This breakage occurs due to a mismatch between the order of collections
and the order of usages on some devices. This commit tries to read the
contact count before processing events, but will fail if the contact
count does not occur prior to the first logical finger collection. This
is the case for devices like the Cintiq Pro 32 which place the contact
count at the very end of the report.

Without the contact count set, touches will only be partially processed.
The `wacom_wac_finger_slot` function will not open any slots since the
number of contacts seen is greater than the expectation of 0, but we will
still end up calling `input_mt_sync_frame` for each finger anyway. This
can cause problems for userspace separate from the issue currently taking
place in the kernel. Only once all of the individual finger collections
have been processed do we finally get to the enclosing collection which
contains the contact count. The value ends up being used for the *next*
report, however.

This delayed use of the contact count can cause the driver to loose track
of the actual touch state and believe that there are contacts down when
there aren't. This leaves touch arbitration enabled and prevents the pen
from working. It can also cause userspace to incorrectly treat single-
finger input as gestures.

Link: https://github.com/linuxwacom/input-wacom/issues/146
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Aaron Armstrong Skomra <aaron.skomra@wacom.com>
Fixes: 15893fa401 ("HID: wacom: generic: read the number of expected touches on a per collection basis")
Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
 		2020-04-16 21:38:47 +02:00
Documentation Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2020-04-01 14:52:59 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2020-04-01 14:52:59 -07:00
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2020-04-01 14:52:59 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-04-01 14:47:40 -07:00
drivers Revert "HID: wacom: generic: read the number of expected touches on a per collection basis" 2020-04-16 21:38:47 +02:00
fs Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-04-01 14:47:40 -07:00
include Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2020-04-01 14:52:59 -07:00
init Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
ipc Revert "ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()" 2020-02-21 11:22:15 -08:00
kernel Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-04-01 14:47:40 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
mm arm64 updates for 5.7: 2020-03-31 10:05:01 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
sound Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
usr initramfs: restore default compression behavior 2020-03-17 09:50:37 +09:00
virt irqchip/gic-v4.1: Move doorbell management to the GICv4 abstraction layer 2020-03-24 12:15:51 +00:00
.clang-format clang-format: Update with the latest for_each macro list 2020-03-06 21:50:05 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore selftest/lkdtm: Use local .gitignore 2020-03-02 08:39:39 -07:00
.mailmap media updates for v5.7-rc1 2020-03-30 13:42:05 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid 2020-04-01 15:18:42 -07:00
Makefile Kbuild updates for v5.7 2020-03-31 16:03:39 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.