[PATCH v9 0/2] HID: multitouch: fix haptic lifetime on delayed input release

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

An open evdev fd can keep the input device alive after HID unbind.
The haptic state in ff->private must remain allocated until the input
device is released, and pending work must finish before HID reports
are freed.

Following Dmitry's v7 and v8 review, hid_haptic_init() now clones the
devres-managed mapping state. FF core owns the clone once setup
succeeds and frees it at final input release.

Patch 1 makes input_ff_create() the last fallible initialization step,
uses __module_get(), and drains pending work through ff->stop at input
unregistration. It also removes the extra HID device reference and
propagates haptic setup failures to mt_probe(), including when hidraw
lets hid_connect() succeed after input setup has failed.

Patch 2 allocates the clone in hid_haptic_init() and transfers it with
no_free_ptr(). It keeps one FF instance per HID device because the
touchpad inputs share report fields.

Changes since v8:
  - clone the mapping state in hid_haptic_init() and give FF core
    ownership of the clone
  - remove the devm release action and extra input/HID references
  - use __module_get() after input_ff_create()
  - propagate haptic initialization errors through mt_probe()
  - drain haptic work at input device unregistration

Build checks on x86_64 with GCC 15.2.0 and W=1 passed: the affected
objects with HID built in, a minimal vmlinux and modules build with
HID=m and HID_MULTITOUCH=m, and hid-multitouch.o with HID_HAPTIC=n.
The full build reported kernel-doc warnings in unmodified files.
A QEMU/KVM boot with KASAN ran 10 virtual UHID haptic cycles: upload and
play an effect, destroy the HID device with evdev still open, then close
the fd. FF_HAPTIC was exposed, output reports were observed, and KASAN
reported no errors. Physical hardware was not tested.

Base: 58161ead29e50d70a317ea26b472e0c7508e69da
v8: https://lore.kernel.org/linux-input/20261016173056.3397211-1-qwe.aldo@gmail.com/

Aldo Ariel Panzardo (2):
  HID: haptic: make FF creation the last fallible init step
  HID: multitouch: give FF core ownership of haptic state

 drivers/hid/hid-haptic.c     | 62 +++++++++++++++++++-----------------
 drivers/hid/hid-haptic.h     |  6 ++--
 drivers/hid/hid-multitouch.c | 18 +++++++++--
 3 files changed, 52 insertions(+), 34 deletions(-)

-- 
2.53.0