[Linuxwacom-devel] udev and serial wacom devices

[Dan Nicholson]

On Mon, Jan 4, 2010 at 3:20 PM, Peter Hutterer <peter.hutterer at who-t.net> wrote:
> On Mon, Jan 04, 2010 at 06:01:09PM -0500, Thomas Jaeger wrote:
>> Hi,
>>
>> I've been trying to get my wacom tablet PC working with the new udev
>> backend.  The digitizer is connected via a serial port and shows up as
>> /dev/ttyS0.  I tried the following udev rules (this is based on an older
>> version of the udev patches that debian and ubuntu ship, I haven't fully
>> comprehended yet how the driver is specified on git master)
>>
>> ACTION=="add|change", SUBSYSTEM=="pnp", ATTR{id}=="WACf*",
>> ENV{NAME}="Serial Wacom Tablet"
>>
>> ACTION=="add|change", SUBSYSTEMS=="pnp", ATTRS{id}=="WACf*",
>> ENV{x11_driver}="wacom"
>>
>> This almost works, except that the current udev code only considers
>> devices whose subsystem in "input", but the subsystem of /dev/ttyS0 is
>> "tty".  The attached patch drops this requirement.  Is this the correct
>> way to re-enable support for serial input devices?
>>
>> Thanks,
>> Tom
>>
>>
>
>> >From e72ebdc6887441ccfae738001995ef686d3496f8 Mon Sep 17 00:00:00 2001
>> From: Thomas Jaeger <ThJaeger at gmail.com>
>> Date: Mon, 4 Jan 2010 15:00:49 -0500
>> Subject: [PATCH] udev: Don't filter subsystem "input"
>>
>> This allows serial wacom devices to work, whose subsystem is "tty".
>> ---
>>  config/udev.c |    6 ------
>>  1 files changed, 0 insertions(+), 6 deletions(-)
>>
>> diff --git a/config/udev.c b/config/udev.c
>> index 3ef0d7f..d73bef5 100644
>> --- a/config/udev.c
>> +++ b/config/udev.c
>> @@ -204,7 +204,6 @@ config_udev_init(void)
>>      struct udev *udev;
>>      struct udev_enumerate *enumerate;
>>      struct udev_list_entry *devices, *device;
>> -    int rc;
>>
>>      udev = udev_new();
>>      if (!udev)
>> @@ -212,10 +211,6 @@ config_udev_init(void)
>>      udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
>>      if (!udev_monitor)
>>          return 0;
>> -    rc = udev_monitor_filter_add_match_subsystem_devtype(udev_monitor,
>> -                                                         "input", NULL);
>> -    if (rc < 0)
>> -        return 0;
>>
>>      if (udev_monitor_enable_receiving(udev_monitor)) {
>>          ErrorF("config/udev: failed to bind the udev monitor\n");
>> @@ -225,7 +220,6 @@ config_udev_init(void)
>>      enumerate = udev_enumerate_new(udev);
>>      if (!enumerate)
>>          return 0;
>> -    udev_enumerate_add_match_subsystem(enumerate, "input");
>>      udev_enumerate_scan_devices(enumerate);
>>      devices = udev_enumerate_get_list_entry(enumerate);
>>      udev_list_entry_foreach(device, devices) {
>> --
>> 1.6.3.3
>
> looks correct but I wonder if it would be better to add tty to the list of
> subsystems instead of parsing all of them?

I don't know if that's going to work completely because the attributes
used for matching get set from the udev ID_INPUT_* variables, and
those only get applied to devices in the input subsystem. See
60-persistent-input.rules and input_id.

What did hal match to set the input capability? I think we essentially
want to do the same thing for udev. Looks like it just matched
input/event* devices.

http://cgit.freedesktop.org/hal/tree/hald/linux/device.c#n1202

Looks like this patch would work as long as ID_INPUT=1 was set for the
device in udev.

--
Dan