On Mon, Feb 24, 2014 at 01:31:54PM -0800, Jason Gerecke wrote:
> This is a re-submission of Ping's earlier touchswitch patches, updated
> to address the bug that I had discovered. Correctly associating the
> correct pen and touch "halves" of a single device under all conditions
> proved to be a bit more difficult than expected, so I've fixed it as
> best I can.
>
> The revised code should work in all cases that worked before, but with
> fewer false-positives and false-negatives. The only tablet I'm aware of
> which still foils the scheme is the Cintiq Companion Hybrid, due to its
> EMR and MFT kernel devices having different names. If somebody is bored
> and familiar with libudev, they might be able to come up with something
> even more accurate.
I found the code below in my junk-code directory, and it works for my 0xE6
here. Benjamin pasted a udevadm output for a 22HDT and the problem there is
that there are multiple parents. So the code we'll need is a bit more
complicated, looks like you need to go up the parents to find the top-most
with ID_VENDOR_ID=056a.
The tree looks something like this:
- USB hub
DEVTYPE=usb_device
ID_VENDOR_ID=xyz
\
- Cintiq_22HDT_HUB
DEVTYPE=usb_device
ID_VENDOR_ID=056a
\
- Cintiq_22HDT_TOUCH
DEVTYPE=usb_device
ID_VENDOR_ID=056a
\
- the "Finger" eventX device is somewhere in here
\
- Cintiq_22HDT_Tablet
DEVTYPE=usb_device
ID_VENDOR_ID=056a
\
- the "Pen" eventX device is somewhere in here
so in pseudocode something like:
next_parent = device;
while (next_parent = udev_device_get_parent_with_subsystem_devtype(next_parent,
"usb", "usb_device")) {
vendor_id = udev_device_get_property_value(next_parent, "ID_VENDOR_ID");
if (strcmp(vendor_id, "056a") == 0)
real_parent = next_parent;
}
then you can get the top-most parent device for the tablet. And that should
be the same for Finger and Touch, regardless of naming, regardless of the
kernel driver being used (Benjamin's udev output used hid-mt, the tree may
be less deep if you have the same kernel driver).
Do that for both devices and if the syspath is the same, you have the same
device. I think, this needs testing with the newer tablets that I don't have
right here, and especially with multiple tablets plugged in too.
And obiously you'll want to use the device's vendor_id, not a hardcoded
string :)
Cheers,
Peter
$> cat udev-same-parent.c
#include <stdio.h>
#include <libudev.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
static struct udev_device *udev_from_file(struct udev *udev, const char
*filename)
{
struct stat st;
stat(filename, &st);
return udev_device_new_from_devnum(udev, 'c', st.st_rdev);
}
int main(int argc, char** argv)
{
int rc = 1;
struct udev *udev = NULL;
struct udev_device *dev1, *dev2 = NULL;
struct udev_device *parent1, *parent2;
const char *syspath1, *syspath2;
if (argc < 3)
goto out;
udev = udev_new();
dev1 = udev_from_file(udev, argv[1]);
dev2 = udev_from_file(udev, argv[2]);
if (!dev1 || !dev2)
goto out;
parent1 = udev_device_get_parent_with_subsystem_devtype(dev1, "usb",
"usb_device");
parent2 = udev_device_get_parent_with_subsystem_devtype(dev2, "usb",
"usb_device");
syspath1 = udev_device_get_syspath(parent1);
syspath2 = udev_device_get_syspath(parent2);
if (strcmp(syspath1, syspath2) == 0)
printf("Yep, they're the same physical device\n");
else
printf("Nope, different devices\n");
out:
udev_device_unref(dev1);
udev_device_unref(dev2);
udev_unref(udev);
return rc;
}
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