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STRUCT FF_DEVICE(9) Input Subsystem STRUCT FF_DEVICE(9)

NAME

struct_ff_device - force-feedback part of an input device

SYNOPSIS

struct ff_device {
  int (* upload) (struct input_dev *dev, struct ff_effect *effect,struct ff_effect *old);
  int (* erase) (struct input_dev *dev, int effect_id);
  int (* playback) (struct input_dev *dev, int effect_id, int value);
  void (* set_gain) (struct input_dev *dev, u16 gain);
  void (* set_autocenter) (struct input_dev *dev, u16 magnitude);
  void (* destroy) (struct ff_device *);
  void * private;
  unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
  struct mutex mutex;
  int max_effects;
  struct ff_effect * effects;
  struct file * effect_owners[];
};

MEMBERS

upload
Called to upload an new effect into device
erase
Called to erase an effect from device
playback
Called to request device to start playing specified effect
set_gain
Called to set specified gain
set_autocenter
Called to auto-center device
destroy
called by input core when parent input device is being destroyed
private
driver-specific data, will be freed automatically
ffbit[BITS_TO_LONGS(FF_CNT)]
bitmap of force feedback capabilities truly supported by device (not emulated like ones in input_dev->ffbit)
mutex
mutex for serializing access to the device
max_effects
maximum number of effects supported by device
effects
pointer to an array of effects currently loaded into device
effect_owners[]
array of effect owners; when file handle owning an effect gets closed the effect is automatically erased

DESCRIPTION

Every force-feedback device must implement upload and playback methods; erase is optional. set_gain and set_autocenter need only be implemented if driver sets up FF_GAIN and FF_AUTOCENTER bits.
Note that playback, set_gain and set_autocenter are called with dev->event_lock spinlock held and interrupts off and thus may not sleep.

COPYRIGHT

January 2017 Kernel Hackers Manual 4.8.