Hi all, There's been many patches and discussions on the synaptics MT work, so I wanted to gather thoughts into one thread to push things forward. First, I want to note something that I think has been overlooked. We've been talking about "ClickPad" devices quite a bit. One can find the product page for these devices at: http://www.synaptics.com/solutions/products/clickpad As a brief overview, ClickPads are an MT surface where the entire surface clicks. The click may be uniform over the touchpad, or it may be hinged on one of the edges. It appears that Takashi has figured out the appropriate bits in the extended capabilities flags to recognized a ClickPad. I can't confirm this, but it sounds like the device emits a middle mouse button click when the touchpad is depressed. Here's the confusing part: Synaptics has a different series of touchpads where only certain regions of the touchpad click. This is the case on my Dell Mini 1012. Unfortunately, I can't find any documentation for these touchpads on Synaptics' website. As another brief overview, my touchpad has two buttons integrated into the bottom ~20% of the touchpad. The left half of the button area clicks separately from the right half, and the device emits left and right buttons as appropriate. The rest of the touchpad is stationary and does not click. If no one has a better name for these touchpads, I'll refer to them as "integrated buttons" touchpads. Also unfortunately, I don't know which cap bits inform us of an integrated buttons touchpad, though I have suspicions it's bit 0x200000 of the 0c extended caps mask. Now onto implementation decisions. I feel that a kernel driver should provide a usable mouse without needing an X input module. There are projects like Wayland that don't use X, and I think people use gpm for consoles still. My definition of a usable mouse is single touch and left click support (including click and drag using a physical button). To answer another recurring question throughout the thread, other MT drivers send both ABS_MT_* and regular ABS_* events. One of the MT touches is assigned for single touch emulation at any given time. This supports legacy user space software that expects ST events while allowing for MT events to be used by more advanced software. I think we should do the same for Synaptics, and we should track the ST emulation touch as Henrik suggested. For ClickPad devices, my feeling is that we should translate middle button clicks to left button clicks in the kernel, and MT+ST emulation should be performed. Middle and right click functionality may be provided for in userspace, like in xf86-input-synaptics or through a gesture stack. I think this level of support meets my personal criteria for kernel level functionality specified above. Integrated buttons devices pose more of a challenge due to the need to properly support click and drag. Lets first assume that we can detect such a touchpad and determine the button area (I'll revisit this later). I think we should disable single touch support over the buttons due to the following scenario: User positions cursor over button on screen, attempts to click physical touchpad button, cursor moves because of motion on touchpad when user depresses button. However, we should support MT over the entire touchpad surface. Perhaps proper filtering and such could make the above scenario work better, and an advanced user space software, like xf86-input-synaptics, could listen to the MT events to get the data if it wants. Integrated buttons have ST emulation support, but only over the non-button area of the touchpad. If a touch moves over the button area, it disappears as far as ST-only aware software is concerned. ST emulation does not switch to another touch because that would look like a dragged touch. Since a touch beginning over the button area is never sent through ST emulation, click and drag will always work no matter which touch goes down first. Now the bit about integrated button touchpad detection. First, I would be interested in learning if anyone can disprove bit 0x200000 of the 0c extended caps flags means integrated buttons. I wonder if we shouldn't solicit for caps bits of various devices too? I'd be happy to look into setting up a web survey form if people think this would be useful. Otherwise, should we try using that bit to see if it works for people or causes regressions? If that bit isn't correct, should we make it a module parameter to enable integrated button functionality? What about button area size? Should we assume it's the same across all such touchpads? I would argue that if we can't detect integrated buttons touchpads we should have a module parameter. I believe we can use udev to specify module parameter quirks for machine types that are known to have integrated buttons. Until we hear of regressions, I would assume the same button area across all such devices. I'd like to reach some sort of consensus before we proceed with more patches, otherwise things will just end up confusing :). I think what I've outlined above should be reasonably easy to implement, the hard part is just agreeing on what is best. Thanks, -- 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
