On Thursday, October 25, 2012 10:11:27 PM Rolf Eike Beer wrote: > You wrote: > > Hi Rolf, > > > > On Thu, Oct 25, 2012 at 02:59:49PM +0200, Rolf Eike Beer wrote: > > > Hi all, > > > > > > as I found out the hard way tslib does the detection if a touchscreen > > > has > > > been "clicked" if the kernel driver says it does not support > > > ABS_PRESSURE. But when the kernel says it can do ABS_PRESSURE tslib will > > > not do it's emulation and just pass on whatever pressure value the > > > kernel > > > sends. > > > > > > So far, so good. Sadly there are some drivers that do: > > > > > > input_set_abs_params(dev, ABS_PRESSURE, 0, 0, 0, 0); > > > > What drivers are doing this? > > git grep 'ABS_PRESSURE, 0, 0, 0, 0' drivers/input/ > > > > Guess what happens: no clicks at all. The question I have is: does the > > > above line make any sense to be in a kernel driver at all? Or is that > > > some voodoo that must be there and it's all tslib fault? > > > > > > Now that I know where the problem is coming from the problem is easily > > > fixable, I'm just wondering which patch to make. > > > > Well, the limits are strictly advisory for userspace, input core does > > not perform any clamping or discarding the data that falls outside the > > limits, so tslib probably should not do that either. > > My main concern is that if the driver says it will only ever give pressure > values from 0 to 0, what useful stuff may that ever be? And since the driver > says it supports presure touchscreen will wait for the driver to report it. > Since it will never do it (or could at most return a 0), then there is > nothing that could ever become a valid click event. Once again, the limits are simply advisory and can even be adjusted from userspace (EVIOCSABS). So ucb1400_ts does report true pressure so all is good there, but tsc40 is not. I think the claim for ABS_PRESSURE is left over from time when tslib did not think that device without ABS_PRESSURE was a touchscreen. I'll remove it from the driver. 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
