[PATCH v7 0/2] hid-steam driver with user mode client dection

[Rodrigo Rivas Costa]

This is a reroll of the Steam Controller driver.

This time the client usage is detected by using exposing a custom hidraw
device (hid_ll_driver) to userland and forwarding that to the real one.

About how the lizard-mode/hidraw-client issue is handled, I have added a
module parameter (I don't know if that is the best option, but it helps me
illustrate different approaches to the problem):

Independently of the lizard_mode parameter value:

 1. When a hidraw client is running:
   a. I will not send any lizard-mode command to the device, so the client is
      in full control.
   b. The input device will not send any input message. However it will not
      dissappear nor return any error message. Maybe it could return ENODEV if
      they try to open the input device when hidraw client is running?

If lizard_mode == 0 ('disabled'):
 2.0. When a hidraw client is not running, lizard_mode is disabled.

If lizard_mode == 1, ('auto', the default):
 2.1. When a hidraw client is not running:
   a. When the input device is not in use, lizard mode is enabled.
   b. When the input device is in use, lizard mode is disabled.

If lizard_mode == 2 ('usermode'):
 2.2. This driver does not send any lizard_mode-related command. So it is up
      to user mode to configure it, with steamctrl or whatever.

Note that when Steam Client opens it always disables lizard-mode (it creates
keyboard/mouse XTest inputs with the same function, though). And when it closed
(but not when it crashes, I think) it always re-enables the lizard mode.

About the input buttons/axes mapping, as per ClÃment suggestion, I tried to
conform to Documentation/gamepad.rst, but with a few caveats and doubts:
 * BTN_NORTH/BTN_WEST are alias of BTN_X/BTN_Y, but those buttons in this
   controller have the labels changed (BTN_NORTH is actually Y). I don't know
   the best option, so for now I'm mapping 'Y' to BTN_Y and 'X' to BTN_X.
 * I'm mapping the lpad clicks to BTN_DPAD_{UP,RIGHT,DOWN,LEFT} but I'm not
   sure if that is such a good idea: it cannot do diagonals, for example.
   Maybe we could fake the whole dpad from the touch position?
 * I'm mapping pressing the joystick to BTN_THUMBL and clicking the rpad to
   BTN_THUMBR. Clicking the lpad is unmapped because that is used for the
   dpad, depending on where it is clicked.
 * Currently I'm mapping the lpad-touch to BTN_THUMB and rpad-touch to
   BTN_THUMB2, but I don't know if that is so useful. lpad-touch will overlap
   with any use of the dpad. And rpad-touch will overlap with rpad-click...

Changes in v7:
 * All the automatic lizard_mode stuff.
 * Added the lizard_mode parameter.
 * The patchset is reduced to 2 commits. The separation of the
   steam_get_serial command no longer makes sense, since I need the
   steam_send_cmd in the first commit to implement the lizard mode.
 * Change the input mapping to conform to Documentation/gamepad.rst.

(v6 was a RFC, it does not count).

Changes in v5:
 * Fix license SPDX to GPL-2.0+.
 * Minor stylistic changes (BIT(3) instead 0x08 and so on).

Changes in v4:
 * Add command to check the wireless connection status on probe, without
   waiting for a message (thanks to ClÃment Vuchener for the tip).
 * Removed the error code on redundant connection/disconnection messages. That
   was harmless but polluted dmesg.
 * Added buttons for touching the left-pad and right-pad.
 * Fixed a misplaced #include from 2/4 to 1/4.

Changes in v3:
 * Use RCU to do the dynamic connec/disconnect of wireless devices.
 * Remove entries in hid-quirks.c as they are no longer needed. This allows
   this module to be blacklisted without side effects.
 * Do not bypass the virtual keyboard/mouse HID devices to avoid breaking
   existing use cases (lizard mode). A user-space tool to do that is
   linked.
 * Fully separated axes for joystick and left-pad. As it happens.
 * Add fuzz values for left/right pad axes, they are a little wiggly.

Changes in v2:
 * Remove references to USB. Now the interesting interfaces are selected by
   looking for the ones with feature reports.
 * Feature reports buffers are allocated with hid_alloc_report_buf().
 * Feature report length is checked, to avoid overflows in case of
   corrupt/malicius USB devices.
 * Resolution added to the ABS axes.
 * A lot of minor cleanups.

Rodrigo Rivas Costa (2):
  HID: add driver for Valve Steam Controller
  HID: steam: add battery device.

 drivers/hid/Kconfig     |   8 +
 drivers/hid/Makefile    |   1 +
 drivers/hid/hid-ids.h   |   4 +
 drivers/hid/hid-steam.c | 978 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/hid.h     |   1 +
 5 files changed, 992 insertions(+)
 create mode 100644 drivers/hid/hid-steam.c

-- 
2.16.2