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
Kernel Hackers Manual 4.8.                 January 2017                       STRUCT FF_DEVICE(9)