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>
Pull input updates from Dmitry Torokhov:
- three new touchscreen drivers: Hycon HY46XX, ILITEK Lego Series,
and MStar MSG2638
- a new driver for Azoteq IQS626A proximity and touch controller
- addition of Amazon Game Controller to the list of devices handled
by the xpad driver
- Elan touchscreen driver will avoid binding to devices described as
I2CHID compatible in ACPI tables
- various driver fixes
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input: (56 commits)
Input: xpad - add support for Amazon Game Controller
Input: ili210x - add missing negation for touch indication on ili210x
MAINTAINERS: repair reference in HYCON HY46XX TOUCHSCREEN SUPPORT
Input: add driver for the Hycon HY46XX touchpanel series
dt-bindings: touchscreen: Add HY46XX bindings
dt-bindings: Add Hycon Technology vendor prefix
Input: cyttsp - flag the device properly
Input: cyttsp - set abs params for ABS_MT_TOUCH_MAJOR
Input: cyttsp - drop the phys path
Input: cyttsp - reduce reset pulse timings
Input: cyttsp - error message on boot mode exit error
Input: apbps2 - remove useless variable
Input: mms114 - support MMS136
Input: mms114 - convert bindings to YAML and extend
Input: Add support for ILITEK Lego Series
dt-bindings: input: touchscreen: ilitek_ts_i2c: Add bindings
Input: add MStar MSG2638 touchscreen driver
dt-bindings: input/touchscreen: add bindings for msg2638
Input: silead - add workaround for x86 BIOS-es which bring the chip up in a stuck state
Input: elants_i2c - do not bind to i2c-hid compatible ACPI instantiated devices
...
ABS_PRESSURE and ABS_MT_PRESSURE on touch devices usually represent
contact size (as a finger flattens with higher pressure the contact size
increases) and userspace translates the kernel pressure value back into
contact size. For example, libinput has pressure thresholds when a touch is
considered a palm (palm == large contact area -> high pressure). The values
themselves are on an arbitrary scale and device-specific.
On pressurepads however, the pressure axis may represent the real physical
pressure. Pressurepads are touchpads without a hinge but an actual pressure
sensor underneath the device instead, for example the Lenovo Yoga 9i.
A high-enough pressure is converted to a button click by the firmware.
Microsoft does not require a pressure axis to be present, see [1], so as seen
from userspace most pressurepads are identical to clickpads - one button and
INPUT_PROP_BUTTONPAD set.
However, pressurepads that export the pressure axis break userspace because
that axis no longer represents contact size, resulting in inconsistent touch
tracking, e.g. [2]. Userspace needs to know when a pressure axis represents
real pressure and the best way to do so is to define what the resolution
field means. Userspace can then treat data with a pressure resolution as
true pressure.
This patch documents that the pressure resolution is in units/gram. This
allows for fine-grained detail and tops out at roughly ~2000t, enough for the
devices we're dealing with. Grams is not a scientific pressure unit but the
alternative is:
- Pascal: defined as force per area and area is unreliable on many devices and
seems like the wrong option here anyway, especially for devices with a
single pressure sensor only.
- Newton: defined as mass * distance/acceleration and for the purposes of a
pressure axis, the distance is tricky to interpret and we get the data to
calculate acceleration from event timestamps anyway.
For the purposes of touch devices and digitizers, grams seems the best choice
and the easiest to interpret.
Bonus side effect: we can use the existing hwdb infrastructure in userspace to
fix devices that advertise false pressure.
[1] https://docs.microsoft.com/en-us/windows-hardware/design/component-guidelines/windows-precision-touchpad-required-hid-top-level-collections#windows-precision-touchpad-input-reports
[2] https://gitlab.freedesktop.org/libinput/libinput/-/issues/562
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20210112230310.GA149342@jelly
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
There is a minor spelling mistake in the documentation, fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Now that the latex_documents are handled automatically, we can
remove those extra conf.py files.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
