Hi, In my machine, sometimes an odd 5 byte packet is received by pms in the 6 byte elantech v4 touchpad protocol as documented in [1]. The packet in question in hex notation is 80 80 36 00 00, which corresponds with a zero movement trackpoint packet missing its first byte which normally carries the trackpoint button states.
As pms assumes 6 bytes per packet with this protocol, receiving a 5 byte packet causes a desynchronisation between the software and hardware state. It is triggered by simultaneous use of any trackpoint button and multi touch input, especially but not necessarily in conjunction with trackpoint movement. The attached patch tests for the specific byte sequence and prepends a null byte such that it is interpreted as a trackpoint button release [2]. Running this patch, the desynchronisation issue no longer occurs, and it seems that no 5 byte packets other then the kind described above are received. Since in the protocol as documented the first byte is never 0x80, I believe that this workaround has no further side effects. As to how and why sometimes this odd packet is received I do not know. It could be that there is a bug in the touchpad firmware, that under some circumstances drops the first byte in a packet if it is null, or perhaps a bug in pms/pckbd that does the same. Perhaps this information is useful. Alexander 1. https://www.kernel.org/doc/html/v4.16/input/devices/elantech.html 2. When just discarding these 5 byte packets I have occasionally observed trackpoint buttons seemingly getting stuck until a new mouse button press. Index: sys/dev/pckbc/pms.c =================================================================== RCS file: /cvs/src/sys/dev/pckbc/pms.c,v retrieving revision 1.90 diff -u -p -r1.90 pms.c --- sys/dev/pckbc/pms.c 20 Sep 2019 21:21:47 -0000 1.90 +++ sys/dev/pckbc/pms.c 19 Jan 2020 12:14:12 -0000 @@ -2382,8 +2382,34 @@ elantech_packet_type(struct elantech_sof int pms_sync_elantech_v4(struct pms_softc *sc, int data) { + int i; + if (sc->inputstate == 0) return ((data & 0x08) == 0 ? 0 : -1); + + /* + * XXX Sometimes an empty trackpoint packet (80 80 36 00 00) + * with missing first byte is received, interpret as trackpoint + * button release. + */ + if (sc->inputstate >= 3 + && (sc->elantech->flags & ELANTECH_F_TRACKPOINT) + && sc->packet[0] == 0x80 + && sc->packet[1] == 0x80 + && sc->packet[2] == 0x36 + && sc->packet[3] == 0x00) { + if (sc->inputstate == 3) + return (0); + else if (sc->packet[4] != 0x00) + return (-1); + else { + for (i = 5; i > 0; i--) + sc->packet[i] = sc->packet[i-1]; + sc->packet[0] = 0x00; + sc->inputstate++; + return (0); + } + } if (sc->inputstate == 3) { switch (elantech_packet_type(sc->elantech, data)) { Packet data sample from a pms patched to print each validated packet: 44 | 0b 3a 32 0c 32 44 | 00 2b 32 fc 27 01 | 80 80 36 00 00 44 | f6 19 32 f3 1c 44 | e6 0b 32 e8 16 pms0: not in sync yet, discard input (state = 3, 80 80 36 00 | e8 16) pms0: not in sync yet, discard input (state = 3, 00 44 b6 fe | e8 16) pms0: not in sync yet, discard input (state = 3, 32 a8 0e 44 | e8 16) pms0: not in sync yet, discard input (state = 0, d8 | a8 0e 44 e8 16) pms0: not in sync yet, discard input (state = 3, f1 32 cb f9 | e8 16) 44 | 94 b6 32 92 ca 44 | c9 d8 32 ce de 44 | cf d1 32 c9 d7 44 | c2 b4 32 b6 b8 44 | cc b5 32 cc bd 44 | da bc 32 e4 cc 01 | 80 80 36 00 00 44 | ef cb 32 f1 cf 44 | fa d2 32 fb d1 dmesg: OpenBSD 6.6-current (GENERIC.MP) #6: Sat Jan 18 11:56:49 CET 2020 XXXXXX@XXXXXXX:/usr/src/sys/arch/amd64/compile/GENERIC.MP real mem = 16908791808 (16125MB) avail mem = 16383868928 (15624MB) mpath0 at root scsibus0 at mpath0: 256 targets mainbus0 at root bios0 at mainbus0: SMBIOS rev. 3.0 @ 0x7f0d6000 (63 entries) bios0: vendor LENOVO version "R0SET49W (1.33 )" date 12/27/2019 bios0: LENOVO 20LHCTO1WW acpi0 at bios0: ACPI 5.0 acpi0: sleep states S0 S3 S4 S5 acpi0: tables DSDT FACP SSDT SSDT TPM2 UEFI SSDT SSDT HPET APIC MCFG ECDT SSDT SSDT BOOT BATB SSDT SSDT SSDT LPIT WSMT SSDT SSDT SSI acpi0: wakeup devices GLAN(S4) XHC_(S3) XDCI(S4) RP01(S4) PXSX(S4) RP02(S4) PXSX(S4) PXSX(S4) RP04(S4) PXSX(S4) RP05(S4) PXSX(S4) R] acpitimer0 at acpi0: 3579545 Hz, 24 bits acpihpet0 at acpi0: 23999999 Hz acpimadt0 at acpi0 addr 0xfee00000: PC-AT compat cpu0 at mainbus0: apid 0 (boot processor) cpu0: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz, 1587.85 MHz, 06-8e-0a cpu0: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PN cpu0: 256KB 64b/line 8-way L2 cache cpu0: smt 0, core 0, package 0 mtrr: Pentium Pro MTRR support, 10 var ranges, 88 fixed ranges cpu0: apic clock running at 24MHz cpu0: mwait min=64, max=64, C-substates=0.2.1.2.4.1.1.1, IBE cpu1 at mainbus0: apid 2 (application processor) cpu1: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz, 1439.83 MHz, 06-8e-0a cpu1: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PN cpu1: 256KB 64b/line 8-way L2 cache cpu1: smt 0, core 1, package 0 cpu2 at mainbus0: apid 4 (application processor) cpu2: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz, 1252.62 MHz, 06-8e-0a cpu2: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PN cpu2: 256KB 64b/line 8-way L2 cache cpu2: smt 0, core 2, package 0 cpu3 at mainbus0: apid 6 (application processor) cpu3: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz, 1141.82 MHz, 06-8e-0a cpu3: FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CFLUSH,DS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE,SSE3,PN cpu3: 256KB 64b/line 8-way L2 cache cpu3: smt 0, core 3, package 0 ioapic0 at mainbus0: apid 2 pa 0xfec00000, version 20, 120 pins acpimcfg0 at acpi0 acpimcfg0: addr 0xf8000000, bus 0-63 acpiec0 at acpi0 acpiprt0 at acpi0: bus 0 (PCI0) acpiprt1 at acpi0: bus 2 (RP01) acpiprt2 at acpi0: bus -1 (RP02) acpiprt3 at acpi0: bus 4 (RP03) acpiprt4 at acpi0: bus -1 (RP04) acpiprt5 at acpi0: bus 5 (RP05) acpiprt6 at acpi0: bus -1 (RP06) acpiprt7 at acpi0: bus -1 (RP07) acpiprt8 at acpi0: bus -1 (RP08) acpiprt9 at acpi0: bus 6 (RP09) acpiprt10 at acpi0: bus -1 (RP10) acpiprt11 at acpi0: bus -1 (RP11) acpiprt12 at acpi0: bus -1 (RP12) acpiprt13 at acpi0: bus -1 (RP13) acpiprt14 at acpi0: bus -1 (RP14) acpiprt15 at acpi0: bus -1 (RP15) acpiprt16 at acpi0: bus -1 (RP16) acpiprt17 at acpi0: bus -1 (RP17) acpiprt18 at acpi0: bus -1 (RP18) acpiprt19 at acpi0: bus -1 (RP19) acpiprt20 at acpi0: bus -1 (RP20) acpiprt21 at acpi0: bus -1 (RP21) acpiprt22 at acpi0: bus -1 (RP22) acpiprt23 at acpi0: bus -1 (RP23) acpiprt24 at acpi0: bus -1 (RP24) acpicpu0 at acpi0: C3(200@1034 mwait.1@0x60), C2(200@151 mwait.1@0x33), C1(1000@1 mwait.1), PSS acpicpu1 at acpi0: C3(200@1034 mwait.1@0x60), C2(200@151 mwait.1@0x33), C1(1000@1 mwait.1), PSS acpicpu2 at acpi0: C3(200@1034 mwait.1@0x60), C2(200@151 mwait.1@0x33), C1(1000@1 mwait.1), PSS acpicpu3 at acpi0: C3(200@1034 mwait.1@0x60), C2(200@151 mwait.1@0x33), C1(1000@1 mwait.1), PSS acpipwrres0 at acpi0: PUBS, resource for XHC_ acpipci0 at acpi0 PCI0: 0x00000010 0x00000011 0x00000000 acpithinkpad0 at acpi0: version 2.0 acpiac0 at acpi0: AC unit offline acpibat0 at acpi0: BAT0 model "01AV433" serial XXXX type LiP oem "SMP" "PNP0C60" at acpi0 not configured "LEN0100" at acpi0 not configured "INT3403" at acpi0 not configured "INT3403" at acpi0 not configured "INT3403" at acpi0 not configured acpicmos0 at acpi0 "INT0E0C" at acpi0 not configured acpibtn0 at acpi0: SLPB acpibtn1 at acpi0: PWRB "PNP0C14" at acpi0 not configured "INT33A1" at acpi0 not configured acpibtn2 at acpi0: LID_ "PNP0C14" at acpi0 not configured "PNP0C14" at acpi0 not configured "PNP0C14" at acpi0 not configured "PNP0C14" at acpi0 not configured "INT3400" at acpi0 not configured "STM7304" at acpi0 not configured "USBC000" at acpi0 not configured acpivideo0 at acpi0: GFX0 acpivout0 at acpivideo0: DD1F cpu0: using VERW MDS workaround (except on vmm entry) cpu0: Enhanced SpeedStep 1587 MHz: speeds: 2001, 2000, 1900, 1800, 1700, 1500, 1400, 1300, 1200, 1100, 1000, 800, 700, 600, 500, 40z pci0 at mainbus0 bus 0 pchb0 at pci0 dev 0 function 0 "Intel Core 8G Host" rev 0x08 inteldrm0 at pci0 dev 2 function 0 "Intel UHD Graphics 620" rev 0x07 drm0 at inteldrm0 inteldrm0: msi "Intel Core 6G Thermal" rev 0x08 at pci0 dev 4 function 0 not configured "Intel Core GMM" rev 0x00 at pci0 dev 8 function 0 not configured "Intel 100 Series ISH" rev 0x21 at pci0 dev 19 function 0 not configured xhci0 at pci0 dev 20 function 0 "Intel 100 Series xHCI" rev 0x21: msi, xHCI 1.0 usb0 at xhci0: USB revision 3.0 uhub0 at usb0 configuration 1 interface 0 "Intel xHCI root hub" rev 3.00/1.00 addr 1 pchtemp0 at pci0 dev 20 function 2 "Intel 100 Series Thermal" rev 0x21 "Intel 100 Series MEI" rev 0x21 at pci0 dev 22 function 0 not configured ppb0 at pci0 dev 28 function 0 "Intel 100 Series PCIE" rev 0xf1: msi pci1 at ppb0 bus 2 rtsx0 at pci1 dev 0 function 0 "Realtek RTS522A Card Reader" rev 0x01: msi sdmmc0 at rtsx0: 4-bit, dma ppb1 at pci0 dev 28 function 2 "Intel 100 Series PCIE" rev 0xf1: msi pci2 at ppb1 bus 4 iwm0 at pci2 dev 0 function 0 "Intel Dual Band Wireless-AC 8265" rev 0x78, msi ppb2 at pci0 dev 28 function 4 "Intel 100 Series PCIE" rev 0xf1: msi pci3 at ppb2 bus 5 nvme0 at pci3 dev 0 function 0 "Samsung SM981/PM981 NVMe" rev 0x00: msix, NVMe 1.2 nvme0: SAMSUNG MZVLB1T0HALR-000L7, firmware 5L2QEXA7, serial XXXXXXXXXXXXXX scsibus1 at nvme0: 2 targets, initiator 0 sd0 at scsibus1 targ 1 lun 0: <NVMe, SAMSUNG MZVLB1T0, 5L2Q> sd0: 976762MB, 512 bytes/sector, 2000409264 sectors ppb3 at pci0 dev 29 function 0 "Intel 100 Series PCIE" rev 0xf1: msi pci4 at ppb3 bus 6 pcib0 at pci0 dev 31 function 0 "Intel 200 Series LPC" rev 0x21 "Intel 100 Series PMC" rev 0x21 at pci0 dev 31 function 2 not configured azalia0 at pci0 dev 31 function 3 "Intel 200 Series HD Audio" rev 0x21: msi azalia0: codecs: Conexant/0x2008, Intel/0x280b, using Conexant/0x2008 audio0 at azalia0 ichiic0 at pci0 dev 31 function 4 "Intel 100 Series SMBus" rev 0x21: apic 2 int 16 iic0 at ichiic0 em0 at pci0 dev 31 function 6 "Intel I219-V" rev 0x21: msi, address 9c:5a:44:1f:b7:65 isa0 at pcib0 isadma0 at isa0 pckbc0 at isa0 port 0x60/5 irq 1 irq 12 pckbd0 at pckbc0 (kbd slot) wskbd0 at pckbd0: console keyboard pms0 at pckbc0 (aux slot) wsmouse0 at pms0 mux 0 pms0: Elantech Clickpad, version 4, firmware 0x4d1f00 wsmouse1 at pms0 mux 0 pcppi0 at isa0 port 0x61 spkr0 at pcppi0 vmm0 at mainbus0: VMX/EPT efifb at mainbus0 not configured uvideo0 at uhub0 port 8 configuration 1 interface 0 "SunplusIT Inc Integrated Camera" rev 2.01/17.91 addr 2 video0 at uvideo0 uhidev0 at uhub0 port 10 configuration 1 interface 0 "Wacom Co.,Ltd. Pen and multitouch sensor" rev 2.00/0.02 addr 3 uhidev0: iclass 3/0, 14 report ids uhid0 at uhidev0 reportid 2: input=0, output=0, feature=1 uhid1 at uhidev0 reportid 3: input=39, output=0, feature=63 uhid2 at uhidev0 reportid 4: input=0, output=0, feature=15 uhid3 at uhidev0 reportid 7: input=0, output=0, feature=255 uhid4 at uhidev0 reportid 8: input=0, output=0, feature=135 uhid5 at uhidev0 reportid 9: input=0, output=0, feature=63 ums0 at uhidev0 reportid 10 ums0: mouse has no X report ums1 at uhidev0 reportid 12: 1 button, tip wsmouse2 at ums1 mux 0 uhid6 at uhidev0 reportid 13: input=0, output=0, feature=7 uhid7 at uhidev0 reportid 14: input=0, output=0, feature=2 uhidev1 at uhub0 port 10 configuration 1 interface 1 "Wacom Co.,Ltd. Pen and multitouch sensor" rev 2.00/0.02 addr 3 uhidev1: iclass 3/0, 19 report ids ums2 at uhidev1 reportid 1: 2 buttons wsmouse3 at ums2 mux 0 uhid8 at uhidev1 reportid 5: input=23, output=0, feature=8 ums3 at uhidev1 reportid 6: 3 buttons, tip, barrel, eraser wsmouse4 at ums3 mux 0 uhid9 at uhidev1 reportid 11: input=15, output=0, feature=63 uhid10 at uhidev1 reportid 15: input=39, output=0, feature=7 uhid11 at uhidev1 reportid 16: input=20, output=0, feature=63 uhid12 at uhidev1 reportid 17: input=0, output=0, feature=9 uhid13 at uhidev1 reportid 18: input=0, output=0, feature=255 ums4 at uhidev1 reportid 19 ums4: mouse has no X report vscsi0 at root scsibus2 at vscsi0: 256 targets softraid0 at root scsibus3 at softraid0: 256 targets sd1 at scsibus3 targ 1 lun 0: <OPENBSD, SR CRYPTO, 006> sd1: 831837MB, 512 bytes/sector, 1703603696 sectors root on sd1a (XXXXXXXXXXXXXXXX.a) swap on sd1b dump on sd1b inteldrm0: 1920x1080, 32bpp wsdisplay0 at inteldrm0 mux 1: console (std, vt100 emulation), using wskbd0 wsdisplay0: screen 1-5 added (std, vt100 emulation) iwm0: hw rev 0x230, fw ver 34.0.1, address a0:51:0b:e9:bb:6e
