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ffe0e7cf29
This reverts commit aaf9978c3c.
Quoting Peter:
There is a HID feature report called "Resolution Multiplier"
Described in the "Enhanced Wheel Support in Windows" doc and
the "USB HID Usage Tables" page 30.
http://download.microsoft.com/download/b/d/1/bd1f7ef4-7d72-419e-bc5c-9f79ad7bb66e/wheel.docx
https://www.usb.org/sites/default/files/documents/hut1_12v2.pdf
This was new for Windows Vista, so we're only a decade behind here. I only
accidentally found this a few days ago while debugging a stuck button on a
Microsoft mouse.
The docs above describe it like this: a wheel control by default sends
value 1 per notch. If the resolution multiplier is active, the wheel is
expected to send a value of $multiplier per notch (e.g. MS Sculpt mouse) or
just send events more often, i.e. for less physical motion (e.g. MS Comfort
mouse).
For the latter, you need the right HW of course. The Sculpt mouse has
tactile wheel clicks, so nothing really changes. The Comfort mouse has
continuous motion with no tactile clicks. Similar to the free-wheeling
Logitech mice but without any inertia.
Note that the doc also says that Vista and onwards *always* enable this
feature where available.
An example HID definition looks like this:
Usage Page Generic Desktop (0x01)
Usage Resolution Multiplier (0x48)
Logical Minimum 0
Logical Maximum 1
Physical Minimum 1
Physical Maximum 16
Report Size 2 # in bits
Report Count 1
Feature (Data, Var, Abs)
So the actual bits have values 0 or 1 and that reflects real values 1 or 16.
We've only seen single-bits so far, so there's low-res and hi-res, but
nothing in between.
The multiplier is available for HID usages "Wheel" and "AC Pan" (horiz wheel).
Microsoft suggests that
> Vendors should ship their devices with smooth scrolling disabled and allow
> Windows to enable it. This ensures that the device works like a regular HID
> device on legacy operating systems that do not support smooth scrolling.
(see the wheel doc linked above)
The mice that we tested so far do reset on unplug.
Device Support looks to be all (?) Microsoft mice but nothing else
Not supported:
- Logitech G500s, G303
- Roccat Kone XTD
- all the cheap Lenovo, HP, Dell, Logitech USB mice that come with a
workstation that I could find don't have it.
- Etekcity something something
- Razer Imperator
Supported:
- Microsoft Comfort Optical Mouse 3000 - yes, physical: 1:4
- Microsoft Sculpt Ergonomic Mouse - yes, physical: 1:12
- Microsoft Surface mouse - yes, physical: 1:4
So again, I think this is really just available on Microsoft mice, but
probably all decent MS mice released over the last decade.
Looking at the hardware itself:
- no noticeable notches in the weel
- low-res: 18 events per 360deg rotation (click angle 20 deg)
- high-res: 72 events per 360deg → matches multiplier of 4
- I can feel the notches during wheel turns
- low-res: 24 events per 360 deg rotation (click angle 15 deg)
- horiz wheel is tilt-based, continuous output value 1
- high-res: 24 events per 360deg with value 12 → matches multiplier of 12
- horiz wheel output rate doubles/triples?, values is 3
- It's a touch strip, not a wheel so no notches
- high-res: events have value 4 instead of 1
a bit strange given that it doesn't actually have notches.
Ok, why is this an issue for the current API? First, because the logitech
multiplier used in Harry's patches looks suspiciously like the Resolution
Multiplier so I think we should assume it's the same thing. Nestor, can you
shed some light on that?
- `REL_WHEEL` is defined as the number of notches, emulated where needed.
- `REL_WHEEL_HI_RES` is the movement of the user's finger in microns.
- `WM_MOUSEWHEEL` (Windows) is is a multiple of 120, defined as "the threshold
for action to be taken and one such action"
https://docs.microsoft.com/en-us/windows/desktop/inputdev/wm-mousewheel
If the multiplier is set to M, this means we need an accumulated value of M
until we can claim there was a wheel click. So after enabling the multiplier
and setting it to the maximum (like Windows):
- M units are 15deg rotation → 1 unit is 2620/M micron (see below). This is
the `REL_WHEEL_HI_RES` value.
- wheel diameter 20mm: 15 deg rotation is 2.62mm, 2620 micron (pi * 20mm /
(360deg/15deg))
- For every M units accumulated, send one `REL_WHEEL` event
The problem here is that we've now hardcoded 20mm/15 deg into the kernel and
we have no way of getting the size of the wheel or the click angle into the
kernel.
In userspace we now have to undo the kernel's calculation. If our click angle
is e.g. 20 degree we have to undo the (lossy) calculation from the kernel and
calculate the correct angle instead. This also means the 15 is a hardcoded
option forever and cannot be changed.
In hid-logitech-hidpp.c, the microns per unit is hardcoded per device.
Harry, did you measure those by hand? We'd need to update the kernel for
every device and there are 10 years worth of devices from MS alone.
The multiplier default is 8 which is in the right ballpark, so I'm pretty
sure this is the same as the Resolution Multiplier, just in HID++ lingo. And
given that the 120 magic factor is what Windows uses in the end, I can't
imagine Logitech rolling their own thing here. Nestor?
And we're already fairly inaccurate with the microns anyway. The MX Anywhere
2S has a click angle of 20 degrees (18 stops) and a 17mm wheel, so a wheel
notch is approximately 2.67mm, one event at multiplier 8 (1/8 of a notch)
would be 334 micron. That's only 80% of the fallback value of 406 in the
kernel. Multiplier 6 gives us 445micron (10% off). I'm assuming multiplier 7
doesn't exist because it's not a factor of 120.
Summary:
Best option may be to simply do what Windows is doing, all the HW manufacturers
have to use that approach after all. Switch `REL_WHEEL_HI_RES` to report in
fractions of 120, with 120 being one notch and divide that by the multiplier
for the actual events. So e.g. the Logitech multiplier 8 would send value 15
for each event in hi-res mode. This can be converted in userspace to
whatever userspace needs (combined with a hwdb there that tells you wheel
size/click angle/...).
Conflicts:
include/uapi/linux/input-event-codes.h -> I kept the new
reserved event in the code, so I had to adapt the revert
slightly
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Harry Cutts <hcutts@chromium.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
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ReStructuredText
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ReStructuredText
.. _input-event-codes:
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=================
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Input event codes
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=================
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The input protocol uses a map of types and codes to express input device values
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to userspace. This document describes the types and codes and how and when they
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may be used.
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A single hardware event generates multiple input events. Each input event
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contains the new value of a single data item. A special event type, EV_SYN, is
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used to separate input events into packets of input data changes occurring at
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the same moment in time. In the following, the term "event" refers to a single
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input event encompassing a type, code, and value.
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The input protocol is a stateful protocol. Events are emitted only when values
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of event codes have changed. However, the state is maintained within the Linux
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input subsystem; drivers do not need to maintain the state and may attempt to
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emit unchanged values without harm. Userspace may obtain the current state of
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event code values using the EVIOCG* ioctls defined in linux/input.h. The event
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reports supported by a device are also provided by sysfs in
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class/input/event*/device/capabilities/, and the properties of a device are
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provided in class/input/event*/device/properties.
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Event types
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===========
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Event types are groupings of codes under a logical input construct. Each
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type has a set of applicable codes to be used in generating events. See the
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Codes section for details on valid codes for each type.
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* EV_SYN:
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- Used as markers to separate events. Events may be separated in time or in
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space, such as with the multitouch protocol.
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* EV_KEY:
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- Used to describe state changes of keyboards, buttons, or other key-like
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devices.
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* EV_REL:
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- Used to describe relative axis value changes, e.g. moving the mouse 5 units
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to the left.
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* EV_ABS:
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- Used to describe absolute axis value changes, e.g. describing the
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coordinates of a touch on a touchscreen.
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* EV_MSC:
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- Used to describe miscellaneous input data that do not fit into other types.
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* EV_SW:
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- Used to describe binary state input switches.
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* EV_LED:
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- Used to turn LEDs on devices on and off.
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* EV_SND:
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- Used to output sound to devices.
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* EV_REP:
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- Used for autorepeating devices.
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* EV_FF:
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- Used to send force feedback commands to an input device.
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* EV_PWR:
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- A special type for power button and switch input.
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* EV_FF_STATUS:
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- Used to receive force feedback device status.
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Event codes
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===========
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Event codes define the precise type of event.
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EV_SYN
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------
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EV_SYN event values are undefined. Their usage is defined only by when they are
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sent in the evdev event stream.
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* SYN_REPORT:
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- Used to synchronize and separate events into packets of input data changes
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occurring at the same moment in time. For example, motion of a mouse may set
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the REL_X and REL_Y values for one motion, then emit a SYN_REPORT. The next
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motion will emit more REL_X and REL_Y values and send another SYN_REPORT.
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* SYN_CONFIG:
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- TBD
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* SYN_MT_REPORT:
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- Used to synchronize and separate touch events. See the
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multi-touch-protocol.txt document for more information.
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* SYN_DROPPED:
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- Used to indicate buffer overrun in the evdev client's event queue.
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Client should ignore all events up to and including next SYN_REPORT
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event and query the device (using EVIOCG* ioctls) to obtain its
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current state.
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EV_KEY
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------
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EV_KEY events take the form KEY_<name> or BTN_<name>. For example, KEY_A is used
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to represent the 'A' key on a keyboard. When a key is depressed, an event with
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the key's code is emitted with value 1. When the key is released, an event is
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emitted with value 0. Some hardware send events when a key is repeated. These
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events have a value of 2. In general, KEY_<name> is used for keyboard keys, and
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BTN_<name> is used for other types of momentary switch events.
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A few EV_KEY codes have special meanings:
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* BTN_TOOL_<name>:
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- These codes are used in conjunction with input trackpads, tablets, and
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touchscreens. These devices may be used with fingers, pens, or other tools.
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When an event occurs and a tool is used, the corresponding BTN_TOOL_<name>
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code should be set to a value of 1. When the tool is no longer interacting
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with the input device, the BTN_TOOL_<name> code should be reset to 0. All
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trackpads, tablets, and touchscreens should use at least one BTN_TOOL_<name>
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code when events are generated.
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* BTN_TOUCH:
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BTN_TOUCH is used for touch contact. While an input tool is determined to be
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within meaningful physical contact, the value of this property must be set
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to 1. Meaningful physical contact may mean any contact, or it may mean
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contact conditioned by an implementation defined property. For example, a
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touchpad may set the value to 1 only when the touch pressure rises above a
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certain value. BTN_TOUCH may be combined with BTN_TOOL_<name> codes. For
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example, a pen tablet may set BTN_TOOL_PEN to 1 and BTN_TOUCH to 0 while the
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pen is hovering over but not touching the tablet surface.
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Note: For appropriate function of the legacy mousedev emulation driver,
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BTN_TOUCH must be the first evdev code emitted in a synchronization frame.
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Note: Historically a touch device with BTN_TOOL_FINGER and BTN_TOUCH was
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interpreted as a touchpad by userspace, while a similar device without
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BTN_TOOL_FINGER was interpreted as a touchscreen. For backwards compatibility
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with current userspace it is recommended to follow this distinction. In the
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future, this distinction will be deprecated and the device properties ioctl
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EVIOCGPROP, defined in linux/input.h, will be used to convey the device type.
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* BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, BTN_TOOL_TRIPLETAP, BTN_TOOL_QUADTAP:
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- These codes denote one, two, three, and four finger interaction on a
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trackpad or touchscreen. For example, if the user uses two fingers and moves
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them on the touchpad in an effort to scroll content on screen,
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BTN_TOOL_DOUBLETAP should be set to value 1 for the duration of the motion.
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Note that all BTN_TOOL_<name> codes and the BTN_TOUCH code are orthogonal in
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purpose. A trackpad event generated by finger touches should generate events
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for one code from each group. At most only one of these BTN_TOOL_<name>
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codes should have a value of 1 during any synchronization frame.
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Note: Historically some drivers emitted multiple of the finger count codes with
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a value of 1 in the same synchronization frame. This usage is deprecated.
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Note: In multitouch drivers, the input_mt_report_finger_count() function should
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be used to emit these codes. Please see multi-touch-protocol.txt for details.
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EV_REL
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------
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EV_REL events describe relative changes in a property. For example, a mouse may
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move to the left by a certain number of units, but its absolute position in
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space is unknown. If the absolute position is known, EV_ABS codes should be used
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instead of EV_REL codes.
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A few EV_REL codes have special meanings:
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* REL_WHEEL, REL_HWHEEL:
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- These codes are used for vertical and horizontal scroll wheels,
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respectively.
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EV_ABS
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------
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EV_ABS events describe absolute changes in a property. For example, a touchpad
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may emit coordinates for a touch location.
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A few EV_ABS codes have special meanings:
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* ABS_DISTANCE:
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- Used to describe the distance of a tool from an interaction surface. This
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event should only be emitted while the tool is hovering, meaning in close
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proximity of the device and while the value of the BTN_TOUCH code is 0. If
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the input device may be used freely in three dimensions, consider ABS_Z
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instead.
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- BTN_TOOL_<name> should be set to 1 when the tool comes into detectable
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proximity and set to 0 when the tool leaves detectable proximity.
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BTN_TOOL_<name> signals the type of tool that is currently detected by the
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hardware and is otherwise independent of ABS_DISTANCE and/or BTN_TOUCH.
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* ABS_MT_<name>:
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- Used to describe multitouch input events. Please see
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multi-touch-protocol.txt for details.
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EV_SW
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-----
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EV_SW events describe stateful binary switches. For example, the SW_LID code is
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used to denote when a laptop lid is closed.
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Upon binding to a device or resuming from suspend, a driver must report
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the current switch state. This ensures that the device, kernel, and userspace
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state is in sync.
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Upon resume, if the switch state is the same as before suspend, then the input
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subsystem will filter out the duplicate switch state reports. The driver does
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not need to keep the state of the switch at any time.
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EV_MSC
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------
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EV_MSC events are used for input and output events that do not fall under other
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categories.
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A few EV_MSC codes have special meaning:
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* MSC_TIMESTAMP:
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- Used to report the number of microseconds since the last reset. This event
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should be coded as an uint32 value, which is allowed to wrap around with
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no special consequence. It is assumed that the time difference between two
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consecutive events is reliable on a reasonable time scale (hours).
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A reset to zero can happen, in which case the time since the last event is
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unknown. If the device does not provide this information, the driver must
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not provide it to user space.
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EV_LED
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------
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EV_LED events are used for input and output to set and query the state of
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various LEDs on devices.
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EV_REP
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------
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EV_REP events are used for specifying autorepeating events.
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EV_SND
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------
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EV_SND events are used for sending sound commands to simple sound output
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devices.
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EV_FF
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-----
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EV_FF events are used to initialize a force feedback capable device and to cause
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such device to feedback.
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EV_PWR
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------
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EV_PWR events are a special type of event used specifically for power
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management. Its usage is not well defined. To be addressed later.
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Device properties
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=================
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Normally, userspace sets up an input device based on the data it emits,
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i.e., the event types. In the case of two devices emitting the same event
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types, additional information can be provided in the form of device
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properties.
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INPUT_PROP_DIRECT + INPUT_PROP_POINTER
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--------------------------------------
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The INPUT_PROP_DIRECT property indicates that device coordinates should be
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directly mapped to screen coordinates (not taking into account trivial
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transformations, such as scaling, flipping and rotating). Non-direct input
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devices require non-trivial transformation, such as absolute to relative
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transformation for touchpads. Typical direct input devices: touchscreens,
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drawing tablets; non-direct devices: touchpads, mice.
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The INPUT_PROP_POINTER property indicates that the device is not transposed
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on the screen and thus requires use of an on-screen pointer to trace user's
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movements. Typical pointer devices: touchpads, tablets, mice; non-pointer
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device: touchscreen.
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If neither INPUT_PROP_DIRECT or INPUT_PROP_POINTER are set, the property is
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considered undefined and the device type should be deduced in the
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traditional way, using emitted event types.
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INPUT_PROP_BUTTONPAD
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--------------------
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For touchpads where the button is placed beneath the surface, such that
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pressing down on the pad causes a button click, this property should be
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set. Common in clickpad notebooks and macbooks from 2009 and onwards.
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Originally, the buttonpad property was coded into the bcm5974 driver
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version field under the name integrated button. For backwards
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compatibility, both methods need to be checked in userspace.
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INPUT_PROP_SEMI_MT
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------------------
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Some touchpads, most common between 2008 and 2011, can detect the presence
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of multiple contacts without resolving the individual positions; only the
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number of contacts and a rectangular shape is known. For such
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touchpads, the semi-mt property should be set.
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Depending on the device, the rectangle may enclose all touches, like a
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bounding box, or just some of them, for instance the two most recent
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touches. The diversity makes the rectangle of limited use, but some
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gestures can normally be extracted from it.
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If INPUT_PROP_SEMI_MT is not set, the device is assumed to be a true MT
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device.
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INPUT_PROP_TOPBUTTONPAD
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-----------------------
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Some laptops, most notably the Lenovo 40 series provide a trackstick
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device but do not have physical buttons associated with the trackstick
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device. Instead, the top area of the touchpad is marked to show
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visual/haptic areas for left, middle, right buttons intended to be used
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with the trackstick.
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If INPUT_PROP_TOPBUTTONPAD is set, userspace should emulate buttons
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accordingly. This property does not affect kernel behavior.
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The kernel does not provide button emulation for such devices but treats
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them as any other INPUT_PROP_BUTTONPAD device.
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INPUT_PROP_ACCELEROMETER
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------------------------
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Directional axes on this device (absolute and/or relative x, y, z) represent
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accelerometer data. Some devices also report gyroscope data, which devices
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can report through the rotational axes (absolute and/or relative rx, ry, rz).
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All other axes retain their meaning. A device must not mix
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regular directional axes and accelerometer axes on the same event node.
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Guidelines
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==========
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The guidelines below ensure proper single-touch and multi-finger functionality.
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For multi-touch functionality, see the multi-touch-protocol.txt document for
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more information.
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Mice
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----
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REL_{X,Y} must be reported when the mouse moves. BTN_LEFT must be used to report
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the primary button press. BTN_{MIDDLE,RIGHT,4,5,etc.} should be used to report
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further buttons of the device. REL_WHEEL and REL_HWHEEL should be used to report
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scroll wheel events where available.
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Touchscreens
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------------
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ABS_{X,Y} must be reported with the location of the touch. BTN_TOUCH must be
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used to report when a touch is active on the screen.
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BTN_{MOUSE,LEFT,MIDDLE,RIGHT} must not be reported as the result of touch
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contact. BTN_TOOL_<name> events should be reported where possible.
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For new hardware, INPUT_PROP_DIRECT should be set.
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Trackpads
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---------
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Legacy trackpads that only provide relative position information must report
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events like mice described above.
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Trackpads that provide absolute touch position must report ABS_{X,Y} for the
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location of the touch. BTN_TOUCH should be used to report when a touch is active
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on the trackpad. Where multi-finger support is available, BTN_TOOL_<name> should
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be used to report the number of touches active on the trackpad.
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For new hardware, INPUT_PROP_POINTER should be set.
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Tablets
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-------
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BTN_TOOL_<name> events must be reported when a stylus or other tool is active on
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the tablet. ABS_{X,Y} must be reported with the location of the tool. BTN_TOUCH
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should be used to report when the tool is in contact with the tablet.
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BTN_{STYLUS,STYLUS2} should be used to report buttons on the tool itself. Any
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button may be used for buttons on the tablet except BTN_{MOUSE,LEFT}.
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BTN_{0,1,2,etc} are good generic codes for unlabeled buttons. Do not use
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meaningful buttons, like BTN_FORWARD, unless the button is labeled for that
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purpose on the device.
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For new hardware, both INPUT_PROP_DIRECT and INPUT_PROP_POINTER should be set.
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