1STRUCT FF_DEVICE(9)             Input Subsystem            STRUCT FF_DEVICE(9)
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NAME

6       struct_ff_device - force-feedback part of an input device
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SYNOPSIS

9       struct ff_device {
10         int (* upload) (struct input_dev *dev, struct ff_effect *effect,struct ff_effect *old);
11         int (* erase) (struct input_dev *dev, int effect_id);
12         int (* playback) (struct input_dev *dev, int effect_id, int value);
13         void (* set_gain) (struct input_dev *dev, u16 gain);
14         void (* set_autocenter) (struct input_dev *dev, u16 magnitude);
15         void (* destroy) (struct ff_device *);
16         void * private;
17         unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
18         struct mutex mutex;
19         int max_effects;
20         struct ff_effect * effects;
21         struct file * effect_owners[];
22       };
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MEMBERS

25       upload
26           Called to upload an new effect into device
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28       erase
29           Called to erase an effect from device
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31       playback
32           Called to request device to start playing specified effect
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34       set_gain
35           Called to set specified gain
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37       set_autocenter
38           Called to auto-center device
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40       destroy
41           called by input core when parent input device is being destroyed
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43       private
44           driver-specific data, will be freed automatically
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46       ffbit[BITS_TO_LONGS(FF_CNT)]
47           bitmap of force feedback capabilities truly supported by device
48           (not emulated like ones in input_dev->ffbit)
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50       mutex
51           mutex for serializing access to the device
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53       max_effects
54           maximum number of effects supported by device
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56       effects
57           pointer to an array of effects currently loaded into device
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59       effect_owners[]
60           array of effect owners; when file handle owning an effect gets
61           closed the effect is automatically erased
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DESCRIPTION

64       Every force-feedback device must implement upload and playback methods;
65       erase is optional.  set_gain and set_autocenter need only be
66       implemented if driver sets up FF_GAIN and FF_AUTOCENTER bits.
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68       Note that playback, set_gain and set_autocenter are called with
69       dev->event_lock spinlock held and interrupts off and thus may not
70       sleep.
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73Kernel Hackers Manual 3.10         June 2019               STRUCT FF_DEVICE(9)
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