HID: core: process the Resolution Multiplier
The Resolution Multiplier is a feature report that modifies the value of Usages within the same Logical Collection. If the multiplier is set to anything but 1, the hardware reports (value * multiplier) for the same amount of physical movement, i.e. the value we receive in the kernel is pre-multiplied. The hardware may either send a single (value * multiplier), or by sending multiplier as many reports with the same value, or a combination of these two options. For example, when the Microsoft Sculpt Ergonomic mouse Resolution Multiplier is set to 12, the Wheel sends out 12 for every detent but AC Pan sends out a value of 3 at 4 times the frequency. The effective multiplier is based on the physical min/max of the multiplier field, a logical min/max of [0,1] with a physical min/max of [1,8] means the multiplier is either 1 or 8. The Resolution Multiplier was introduced for high-resolution scrolling in Windows Vista and is commonly used on Microsoft mice. The recommendation for the Resolution Multiplier is to default to 1 for backwards compatibility. This patch adds an arbitrary upper limit at 255. The only known use case for the Resolution Multiplier is for scroll wheels where the multiplier has to be a fraction of 120 to work with Windows. Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net> Verified-by: Harry Cutts <hcutts@chromium.org> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
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