Hi all, I'd like to get your opinion on a proposal for a small change to the hid-multitouch driver. As you probably know this driver supports multi touch input for various touchscreen/touchpad devices. The change relates to lines 654 & 655 of "hid-multitouch.c" - I would like to remove the "division by 2" applied to the "touch width" and "touch height" values received from the input device. These values represent the width and height of the area occupied by a finger touching the input device. https://github.com/torvalds/linux/blame/master/drivers/ hid/hid-multitouch.c#L654 This division by 2 was added along with the the touch width/height fields 6 years ago so that those fields "match the visual scale of the touch" for a specific device (3M PCT) - see comment & associated commit log for line 653. I don't think that this scaling is appropriate for all the other devices that this driver now supports. On my screen for example (Elan multitouch screen), the touch width and height reported bear no relation to the "visual scale of the touch" with or without this /2 scaling applied. I suspect that the scale of touch width/height values reported are different for every device (though I've not checked any other device). The scaling is also discarding information about touch size (1 bit for each of width/height) which is useful for any application that wants to know about it. So in summary I think the main questions for you are: 1. would making this change have a negative effect on any existing applications that use this information? 2. does it seem sensible to (continue to) provide touch width/height values that bear no relation to screen/pixel dimensions? I delved into this because I wanted to get as much precision on touch width/height as possible and was surprised at the low resolution of sizes output by my touchscreen. I got an extra 2 bits of precision from my search! Cheers & thanks for reading. Jonathan -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
