On Sat, Jul 21, 2012 at 2:31 AM, Chase Douglas <chase.doug...@canonical.com> wrote: > > On 07/20/2012 02:03 AM, Daniel Kurtz wrote: >>>>>> >>>>>> * Leave the device as SEMI_MT, but provide the real locations, and >>>>>> allow userspace to determine the device vendor/model/etc. If >>>>>> userspace knows that a specific device behaves in a specific way, it >>>>>> can do its own quirking handling. Given the specificity of this >>>>>> behavior to only some devices of one brand, this would be my >>>>>> suggested resolution to the issue. >> >> >> This is essentially what this patch does. It sets the SEMI_MT flag to >> indicate that the kernel data cannot be totally trusted, and then >> provides real MT-B (including per-finger pressures), instead of a >> fixed bounding box. It leaves it to userspace to treat the two slots >> worth of coordinates as a bounding box or as actual fingers using its >> own heuristics. By limiting to only one hardware type (using DMI), >> any breakage caused by this alternative use of the SEMI_MT flag is >> limited. > > > So I was worried that you were trying to remove the SEMI_MT flag, and I > apologise for not looking closely enough to notice that wasn't the case. The > documentation for the flag says: > > """ > Some touchpads, most common between 2008 and 2011, can detect the presence of > multiple contacts without resolving the individual positions; only the number > of contacts and a rectangular shape is known. For such touchpads, the semi-mt > property should be set. > > Depending on the device, the rectangle may enclose all touches, like a > bounding box, or just some of them, for instance the two most recent touches. > The diversity makes the rectangle of limited use, but some gestures can > normally be extracted from it. > """ > > Since the documentation doesn't say the data must be provided as min/max > values, this patch actually appears to be perfectly fine as is. > > My next question is: how are you going to tell from userspace if the hardware > actually provides correct data? IIRC, it was decided that we wouldn't provide > sysfs nodes for the device IDs. >
Excellent question. We haven't solved this in any elegant way. When building images for this particular hardware platform, we set a flag in our user-space touchpad driver. It then knows to process this device's data as "non-bounding box semi-mt". -Daniel > -- Chase > > -- > To unsubscribe from this list: send the line "unsubscribe linux-input" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
