Hi folks, I've recently acquired a Thinkpad x230t, which has a Wacom touchscreen (vendor/product: 056a:00e6).
When moving my finger around quickly on the screen (especially evident when dragging a window around in X) there is a noticeable lag. I added some debugging statements in wacom_wac.c:wacom_tpc_mt_touch() and verified that the lag is visible at the kernel level, rather than being some X vsync artifact or something. I then noticed that my debugging printk's were being called every 8 or 12 milliseconds, alternating: [14265.968153 < 0.011958>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1580, y: 783 [14265.976128 < 0.007975>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1589, y: 790 [14265.988148 < 0.012020>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1599, y: 798 [14265.996128 < 0.007980>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1610, y: 806 [14266.008023 < 0.011895>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1622, y: 814 [14266.016000 < 0.007977>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1633, y: 822 [14266.027994 < 0.011994>] wacom 2-1.5:1.1: wacom_tpc_mt_touch: x: 1645, y: 831 (`dmesg -d` is what reports the delta) It seems like others have reported similar[1]. The endpoint interval for the Finger interface is 5 frames, which I believe translates to 5 ms (I'm new to the USB stack, please correct any errors I have!): [13496.745718] wacom: endpoint interval: 7 [13496.745784] input: Wacom ISDv4 E6 Pen /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.5/2-1.5:1.0/input/input38 [13496.750724] wacom: endpoint interval: 5 [13496.750815] input: Wacom ISDv4 E6 Finger as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.5/2-1.5:1.1/input/input39 And I see the wacom driver initializes a single URB, which re-submits itself at the end of it's callback, which seems to be the common idiom. I guess I'm looking to see if there is anything I can do to try to get data faster/with less lag from the device (can I try manually decreasing endpoint->bInterval, or will that just cause instability/Bad Things?), or how I would debug this in a better way. Let me know what additional data I can provide as well. thanks! yours, Bobby 1 - http://old.nabble.com/Pen-Cursor-lag-on-Wacom-on-Asus-Slate-ep121-to32360422.html ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnmore_123012 _______________________________________________ Linuxwacom-devel mailing list Linuxwacom-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxwacom-devel
