Re: [PATCH 2/2] Input - synaptics: pin 3 touches when the firmware reports 3 fingers
From: Benjamin Tissoires <hidden>
Date: 2015-06-11 17:29:16
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On Apr 24 2015 or thereabouts, Benjamin Tissoires wrote:
Hi Dmitry, [ adding more relevant people to the discussion ] On Apr 23 2015 or thereabouts, Benjamin Tissoires wrote:quoted
On Apr 23 2015 or thereabouts, Dmitry Torokhov wrote:quoted
On Wed, Apr 22, 2015 at 11:45:09AM -0400, Benjamin Tissoires wrote:quoted
Synaptics PS/2 touchpad can send only 2 touches in a report. They can detect 4 or 5 and this information is valuable. In commit 63c4fda3c0bb ("Input: synaptics - allocate 3 slots to keep stability in image sensors"), we allocate 3 slots, but we still continue to report the 2 available fingers. That means that the client sees 2 used slots while there is a total of 3 fingers advertised by BTN_TOOL_TRIPLETAP. For old kernels this is not a problem because max_slots was 2 and libinput/ xorg-synaptics knew how to deal with that. Now that max_slot is 3, the clients ignore BTN_TOOL_TRIPLETAP and count the actual used slots (so 2). It then gets confused when receiving the BTN_TOOL_TRIPLETAP and DOUBLETAP information, and goes wild. We can pin the 3 slots until we get a total number of fingers below 2. Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1212230Benjamin, I do not quite like it. It seems that original patch was not quite right and we are adding more workarounds.Agree. And I am starting to hate more and more the synaptics PS/2 and all the PS/2 drivers to be honest :) - trying to fit a heavy load data like multitouch in a simple and lightweight protocol like PS/2 is insane... We are internally trying to figure out if we can finally take advantage of the SMBus/RMI4 protocol, but we tried for one year without much success.quoted
Synaptics can only track 2 contacts, correct? Why 2 slots to track them is not enough?IIRC, the problem was that upon a third finger down, with only 2 slots, the fingers were silently inverted in most cases. The thing is that the firmware forwards 2 fingers, but not necessarily the two first. So you generally get fingers 1+3 so the slot 2 needs to be removed. And that means the kernel tracking has to track 3 fingers upon transitions. This may be completely bullshit and we might not need to use 3 slots at all. I'll need to do further experiments to validate which one is best then. I am perfectly fine holding this one up for a little bit more testings and then we can decide which one needs to be done (revert or an other band-aid).So I carefully recorded each situation (initial with 2 slots, 2 slots and then with the pinning in this patch*), and I am now convinced that the pinning is the best sequence that we forward to the user space (best among the 3). With 2 slots declared, there are 2 problems: - the first finger jumps to the position of the 3rd when it lands - the transition between 2 to 3 fingers goes to a state where the kernel removes the second finger (while jumping the first to the position of the 3rd finger), send a sync and then reallocate the first finger position as the second slot in use -> that means that user space sees a small transition where the slots count is 1 while the BTN_TOOL advertise triple tap :/ With 3 slots, we have the problem reported in the rhbz bug #1212230: - during the transition, the fingers are stable, but we have at most 2 active slots in one frame, which confuses libinput/xorg-synaptics. With the pinning, the user space is no more confused because BTN_TOOL is always greater or equal than the active slots. So I think for now we have 3 possibilities: 1. Just carry this patch, and hope that we will be able to switch the synaptics device in the non-PS/2 mode 2. Revert to 2 patches and fix the kernel tracking to accept 3 fingers and return the 2 best matches 3. Revert the use of the kernel tracking at all and re-introduce the spaghetti code that was here before and hope that all cases where properly handled. IMO that the solution 2. is the best, but I can not do it because I don't understand what the code does. I can guess things but I can not accurately change it because it is not readable IMO. (yes, there is also the solution 4: "screw up and let the user space deal with it", but I'd rather not do that given the history of the multitouch protocol)
Dmitry, I feel like this discussion fell a little bit between the cracks and that we all forgot about it. I still believe that the patch is needed (even if it is not the best solution), so I am sending a gently ping on this one :) Cheers, Benjamin
quoted hunk ↗ jump to hunk
* I tried to put side by side the 3 test cases in the following logs: (init slots 2, no pinning) | (init slots 3, no pinning) | (init slots 3, pinning) ----------------------------- | ----------------------------- | --------------------------- ------------------------------|----- one finger down -------|---------------------------- | | ABS_MT_SLOT 0 | ABS_MT_SLOT 0 | ABS_MT_SLOT 0 ABS_MT_TRACKING_ID 53 | ABS_MT_TRACKING_ID 53 | ABS_MT_TRACKING_ID 53 ABS_MT_POSITION_X 2000 | ABS_MT_POSITION_X 2000 | ABS_MT_POSITION_X 2000 ABS_MT_POSITION_Y 2000 | ABS_MT_POSITION_Y 2000 | ABS_MT_POSITION_Y 2000 ABS_MT_PRESSURE 68 | ABS_MT_PRESSURE 68 | ABS_MT_PRESSURE 68 BTN_TOUCH 1 | BTN_TOUCH 1 | BTN_TOUCH 1 ABS_X 2000 | ABS_X 2000 | ABS_X 2000 ABS_Y 2000 | ABS_Y 2000 | ABS_Y 2000 ABS_PRESSURE 68 | ABS_PRESSURE 68 | ABS_PRESSURE 68 BTN_TOOL_FINGER 1 | BTN_TOOL_FINGER 1 | BTN_TOOL_FINGER 1--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | |... | ... | ... | | ------------------------------------ second finger down ------------------------------------ | |--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ----------ABS_MT_POSITION_X 2000 | ABS_MT_POSITION_X 2000 | ABS_MT_POSITION_X 2000 ABS_MT_POSITION_Y 2000 | ABS_MT_POSITION_Y 2000 | ABS_MT_POSITION_Y 2000 ABS_MT_PRESSURE 78 | ABS_MT_PRESSURE 78 | ABS_MT_PRESSURE 78 ABS_MT_SLOT 1 | ABS_MT_SLOT 1 | ABS_MT_SLOT 1 ABS_MT_TRACKING_ID 54 | ABS_MT_TRACKING_ID 54 | ABS_MT_TRACKING_ID 54 ABS_MT_POSITION_X 3000 | ABS_MT_POSITION_X 3000 | ABS_MT_POSITION_X 3000 ABS_MT_POSITION_Y 3000 | ABS_MT_POSITION_Y 3000 | ABS_MT_POSITION_Y 3000 ABS_MT_PRESSURE 64 | ABS_MT_PRESSURE 64 | ABS_MT_PRESSURE 64 ABS_X 2000 | ABS_X 2000 | ABS_X 2000 ABS_Y 2000 | ABS_Y 2000 | ABS_Y 2000 ABS_PRESSURE 78 | ABS_PRESSURE 78 | ABS_PRESSURE 78 BTN_TOOL_FINGER 0 | BTN_TOOL_FINGER 0 | BTN_TOOL_FINGER 0 BTN_TOOL_DOUBLETAP 1 | BTN_TOOL_DOUBLETAP 1 | BTN_TOOL_DOUBLETAP 1--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | |... | ... | ... | | ------------------------------------ third finger down ------------------------------------ | |--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ----------ABS_MT_SLOT 0 | ABS_MT_SLOT 0 | ABS_MT_SLOT 0 ABS_MT_POSITION_X 4000 | ABS_MT_POSITION_X 2000 | ABS_MT_POSITION_X 2000 ABS_MT_POSITION_Y 4000 | ABS_MT_POSITION_Y 2000 | ABS_MT_POSITION_Y 2000 ABS_MT_PRESSURE 78 | ABS_MT_PRESSURE 78 | ABS_MT_PRESSURE 78 ABS_MT_SLOT 1 | ABS_MT_SLOT 2 | ABS_MT_SLOT 2 ABS_MT_TRACKING_ID -1 | ABS_MT_TRACKING_ID 55 | ABS_MT_TRACKING_ID 55 | ABS_MT_POSITION_X 4000 | ABS_MT_POSITION_X 4000 | ABS_MT_POSITION_Y 4000 | ABS_MT_POSITION_Y 4000 | ABS_MT_PRESSURE 72 | ABS_MT_PRESSURE 72 | ABS_MT_SLOT 1 | | ABS_MT_TRACKING_ID -1 | ABS_X 4000 | ABS_X 2000 | ABS_X 2000 ABS_Y 4000 | ABS_Y 2000 | ABS_Y 2000 ABS_PRESSURE 78 | ABS_PRESSURE 78 | ABS_PRESSURE 78 BTN_TOOL_DOUBLETAP 0 | BTN_TOOL_DOUBLETAP 0 | BTN_TOOL_DOUBLETAP 0 BTN_TOOL_TRIPLETAP 1 | BTN_TOOL_TRIPLETAP 1 | BTN_TOOL_TRIPLETAP 1--- SYN_REPORT (0) ---------- | |ABS_MT_SLOT 0 | | ABS_MT_POSITION_X 4000 | | ABS_MT_POSITION_Y 4000 | | ABS_MT_PRESSURE 78 | | ABS_MT_SLOT 1 | | ABS_MT_TRACKING_ID 55 | | ABS_MT_POSITION_X 2000 | | ABS_MT_POSITION_Y 2000 | | ABS_MT_PRESSURE 72 | | ABS_X 4000 | | ABS_Y 4000 | | ABS_PRESSURE 78 | |--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | |... | ... | ... | | ------------------------------------ 3 fingers release ------------------------------------ | | | |--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | | ABS_MT_SLOT 2 | | ABS_MT_POSITION_X 4000 | | ABS_MT_POSITION_Y 4000 | | ABS_MT_PRESSURE 45ABS_MT_SLOT 0 | ABS_MT_SLOT 0 | ABS_MT_SLOT 0 ABS_MT_TRACKING_ID -1 | ABS_MT_TRACKING_ID -1 | ABS_MT_TRACKING_ID -1 ABS_MT_SLOT 1 | ABS_MT_SLOT 2 | ABS_MT_SLOT 1 ABS_MT_TRACKING_ID -1 | ABS_MT_TRACKING_ID -1 | ABS_MT_TRACKING_ID -1 | | ABS_X 4000 | | ABS_Y 4000 BTN_TOUCH 0 | BTN_TOUCH 0 | ABS_PRESSURE 45 ABS_PRESSURE 0 | ABS_PRESSURE 0 | BTN_TOOL_FINGER 1 BTN_TOOL_TRIPLETAP 0 | BTN_TOOL_TRIPLETAP 0 | BTN_TOOL_TRIPLETAP 0--- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | --- SYN_REPORT (0) ---------- | | ABS_MT_SLOT 2 | | ABS_MT_TRACKING_ID -1 | | BTN_TOUCH 0 | | ABS_PRESSURE 0 | | BTN_TOOL_FINGER 0 | | --- SYN_REPORT (0) ----------