On 08/18/2011 12:47 AM, Dmitry Torokhov wrote: > On Thu, Aug 18, 2011 at 09:57:05AM +0800, JJ Ding wrote: >> + >> + i = (etd->fw_version > 0x020800 && >> + etd->fw_version < 0x020900) ? 1 : 2; >> + *x_max = (etd->capabilities[1] - i) * 64; >> + *y_max = (etd->capabilities[2] - i) * 64; >> + *y_2ft_max = (*y_max - i) * 64 / 4; > > Hmm, we should have the same range for ST and MT data and scale MT data > if it has lower resolution to match ST. I saw this go by a while back and it made sense to me at the time. However, I've had some thoughts that give me pause. Seth Forshee has been working on getting a semi-mt driver for ALPS devices. The ALPS devices have an interesting mechanism for providing multitouch data, but it boils down to having a resolution of only 15 values in the X axis and 11 in the Y axis (it looks possible to extrapolate and get double the resolution, but my point will remain). Let's take the X synaptics module as an example of the repercussions of in-kernel axis scaling. The X synaptics module translates two touch drags into scroll events. Synaptics will want to use the highest resolution axis for generating scroll events. If both the MT and ST axes have the same resolution, it might pick the MT axes for scrolling. On ALPS devices with in-kernel axis scaling that would be a bad choice. It's trivial to project the MT and ST axes onto each other in userspace. I suggest we report the real range and resolution of ST and MT axes independently. -- Chase -- 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
