On Mon, Jan 24, 2011 at 7:49 AM, Chris Bagwell <[email protected]> wrote: > Hi Ping, > > I'm trying to catch up with you in understanding... You mentioned > elsewhere that HW is reporting physical size in terms of 0.001 of a > cm.
Not just elsewhere :). It is also in this patch's commit comments (the second line ;). > Assuming thats true (what a crazy unit!), then the HID spec shows > how to compute resolution like this: > > resolution in units per cm = logical_size / (physical_size * 10-3) > > Would you mind changing your math below to be closer to HID spec? I > think it will help readers understand faster if they've read HID spec > first. So I mean change like this: > > resolution in units per meter = logical_size / (physical_size * 0.1) I got questions for using this type of forms at linux-input ;). > It would be cool if HID turns out to be reporting in terms of mm > (10^-1 or 0.1 of cm). Then it reduces to: > > resolution in units per meter = logical_size / physical_size > > I have one more comment below. > > On Mon, Jan 24, 2011 at 1:39 AM, Ping Cheng <[email protected]> wrote: >> resolution = logical size / physical size >> >> The touch physical size we get from the kernel is in thousandth cm. >> The resolution unit we need to report to XInput is in point/m. So, >> >> touch resolution = logical size * 10 / physical size >> >> Signed-off-by: Ping Cheng <[email protected]> >> --- >> src/wcmUSB.c | 24 ++++++++++-------------- >> 1 files changed, 10 insertions(+), 14 deletions(-) >> >> diff --git a/src/wcmUSB.c b/src/wcmUSB.c >> index cfaf920..d8e8312 100644 >> --- a/src/wcmUSB.c >> +++ b/src/wcmUSB.c >> @@ -483,33 +483,29 @@ int usbWcmGetRanges(InputInfoPtr pInfo) >> common->wcmMaxTouchY = absinfo.maximum; >> >> /* max finger strip X for tablets with Expresskeys >> - * or touch physical X for TabletPCs with touch */ >> + * or physical X for touch device in thousandth cm */ >> if (ioctl(pInfo->fd, EVIOCGABS(ABS_RX), &absinfo) == 0) >> { >> - if (is_touch) >> - common->wcmTouchResolX = absinfo.maximum; >> + if (is_touch && !common->wcmTouchResolX) >> + common->wcmTouchResolX = >> + (int)(((double)common->wcmMaxTouchX * 10.0 >> + / (double)absinfo.maximum) + 0.5); > > This gives preference to the lookup table instead of hardware. Maybe > we should give preference to HW reported value (and fall back to > table)? Good point. I'll think about it a bit more. The issue isn't as simple as just a HW reported v.s. a table. We are dealing with three cases: non-touch devices; touch devices with resolution reported through RX/RY for kernels older than 2.6.35; and resolution supported by the new EVIOC. For non-touch devices, the resolution is per-model based. Each product ID has a predefined resolution which we can not retrieve from HID. That's why we had the table. If we want to get the resolution for those devices from the kernel, we would need to move the table to the kernel driver. Since touch and pen enabled devices share the same product ID, touch resolution is default to pen resolution until we get it from the kernel. When we get it from the kernel, we may get it by RX/RY or input_absinfo depending on which kernel we are going to use. My intention for "if (is_touch && !common->wcmTouchResolX)" was to give preference to input_absinfo over RX/RY. But I neglected the fact that wcmTouchResolX has already had a default value when absinfo.resolution is not supported. I'll make a version 2. I think it would be easier to merge the two patches into one since they both deal with the same issue. > + if (is_touch && absinfo.maximum) > > It doesn't really matter much since this is code that will not be used > with any new HW. Why? It will be for all touch devices that report resolution through input_absinfo. Or maybe I missed your point? Thanks. Ping > Chris > >> else >> common->wcmMaxStripX = absinfo.maximum; >> } >> >> /* max finger strip Y for tablets with Expresskeys >> - * or touch physical Y for TabletPCs with touch */ >> + * or physical Y for touch device in thousandth cm */ >> if (ioctl(pInfo->fd, EVIOCGABS(ABS_RY), &absinfo) == 0) >> { >> - if (is_touch) >> - common->wcmTouchResolY = absinfo.maximum; >> + if (is_touch && !common->wcmTouchResolY) >> + common->wcmTouchResolY = >> + (int)(((double)common->wcmMaxTouchY * 10.0 >> + / (double)absinfo.maximum) + 0.5); >> else >> common->wcmMaxStripY = absinfo.maximum; >> } >> >> - if (is_touch && common->wcmTouchResolX && common->wcmMaxTouchX) >> - { >> - common->wcmTouchResolX = >> (int)(((double)common->wcmTouchResolX) >> - / ((double)common->wcmMaxTouchX) + 0.5); >> - common->wcmTouchResolY = >> (int)(((double)common->wcmTouchResolY) >> - / ((double)common->wcmMaxTouchY) + 0.5); >> - } >> - >> /* max z cannot be configured */ >> if (ioctl(pInfo->fd, EVIOCGABS(ABS_PRESSURE), &absinfo) == 0) >> common->wcmMaxZ = absinfo.maximum; >> -- >> 1.7.3.4 >> >> >> ------------------------------------------------------------------------------ >> Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)! >> Finally, a world-class log management solution at an even better price-free! >> Download using promo code Free_Logger_4_Dev2Dev. 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