On Fri, Jan 28, 2011 at 10:23:59AM -0800, Ping Cheng wrote: > On Fri, Jan 28, 2011 at 9:30 AM, Henrik Rydberg <rydberg@xxxxxxxxxxx> wrote: > > Hi Ping, > > > >> This is mainly required by the serial pen and touch devices since > >> both pen and touch are on the same port. Updated the USB ones to > >> keep MT event definition consistent among serial and USB devices. > > > > Why is this change performed? What does the patch do? Please elaborate > > a little bit. > > Let's see if I can explain it clearer or not. > > We need to report resolution to userland for wacom_w8001.c. Since pen > and touch data are reported through the same logical port for serial > devices, using input_abs_set_res for ABS_X/Y, we can only pass the > resolution for pen or touch. So, I let ABS_X/Y report pen resolution > since most legacy ST clients process pen data over touch. However, for > multi-touch clients, especially for those that support gestures, touch > resolution is needed to calculate the physical distance between two > touch points. Using ABS_MT_POSITION_X/Y does not cause confusion and > it is quite intuitive. We just went through the round of why we should scale events from different tools when they use the same event devices and I do not see why MT data is any different. Devices have only one set of physical axes (MT or not) so I believe min, max and resultion should be reported on ABS_X, Y, X, etc, or, if you want to have this data in ABS_MT_POSITION, it should be trhe same. ABS_MT_POSITION is just a vehicle of delivering multipe contacts, not a new device axis. Thanks. -- Dmitry -- 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
