HID: input: Create a utility class for counting scroll events

To avoid code duplication, this class counts high-resolution scroll
movements and emits the legacy low-resolution events when appropriate.
Drivers should be able to create one instance for each scroll wheel that
they need to handle.

Signed-off-by: Harry Cutts <hcutts@chromium.org>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 28 insertions, 0 deletions

diff --git a/include/linux/hid.h b/include/linux/hid.h
index 834e6461a690..037e37b0b0e6 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1138,6 +1138,34 @@ static inline u32 hid_report_len(struct hid_report *report)
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
 		int interrupt);
 
+
+/**
+ * struct hid_scroll_counter - Utility class for processing high-resolution
+ *                             scroll events.
+ * @dev: the input device for which events should be reported.
+ * @microns_per_hi_res_unit: the amount moved by the user's finger for each
+ *                           high-resolution unit reported by the mouse, in
+ *                           microns.
+ * @resolution_multiplier: the wheel's resolution in high-resolution mode as a
+ *                         multiple of its lower resolution. For example, if
+ *                         moving the wheel by one "notch" would result in a
+ *                         value of 1 in low-resolution mode but 8 in
+ *                         high-resolution, the multiplier is 8.
+ * @remainder: counts the number of high-resolution units moved since the last
+ *             low-resolution event (REL_WHEEL or REL_HWHEEL) was sent. Should
+ *             only be used by class methods.
+ */
+struct hid_scroll_counter {
+	struct input_dev *dev;
+	int microns_per_hi_res_unit;
+	int resolution_multiplier;
+
+	int remainder;
+};
+
+void hid_scroll_counter_handle_scroll(struct hid_scroll_counter *counter,
+				      int hi_res_value);
+
 /* HID quirks API */
 unsigned long hid_lookup_quirk(const struct hid_device *hdev);
 int hid_quirks_init(char **quirks_param, __u16 bus, int count);