[Pkg-utopia-maintainers] Bug#562052: Correctly identify touchpads

[Michael Tokarev]

Martin Pitt wrote:
> Michael Tokarev [2009-12-25  1:51 +0300]:
>>> Not really :( We print in groups of longs so it is either 32 or 64 bits
>>> worth of data per number.
>> Ok, I stand corrected.  I verified the issue with 32bit kernel, and
>> there, hald works as expected, listing `synaptics' as x11_driver
>> and correct input.touchpad capability.
> 
> Just to have all the data, could you please find the input device
> number (from lshal, as you did before), and send the output of
> 
>   cat /sys/class/input/inputX/capabilities/key
> 
> (replace X with the particular input device number) under a 32 and 64
> bit system?

It's shown in /proc/bus/input/devices too.  Sure I can, here we go:

32bit: 6420 0 7000f 0 0 0 0 0 0 0 0
64bit: 6420 7000f 0 0 0 0

> Also, do you get correct or wrong ID_INPUT_* flags for the synaptics
> device in "udevadm info --export-db|less"? I expect it to be wrong as
> well, since it's pretty much the same code.

in both cases userspace is 32bit, but kernel bitness is different:

32bit:
P: /devices/platform/i8042/serio4/input/input9
E: UDEV_LOG=3
E: DEVPATH=/devices/platform/i8042/serio4/input/input9
E: PRODUCT=11/2/7/12b1
E: NAME="SynPS/2 Synaptics TouchPad"
E: PHYS="isa0060/serio4/input0"
E: EV==b
E: KEY==6420 0 7000f 0 0 0 0 0 0 0 0
E: ABS==11000003
E: MODALIAS=input:b0011v0002p0007e12B1-e0,1,3,k100,101,102,103,110,111,112,145,14A,14D,14E,ra0,1,18,1C,mlsfw
E: SUBSYSTEM=input

64bit:
P: /devices/platform/i8042/serio4/input/input9
E: UDEV_LOG=3
E: DEVPATH=/devices/platform/i8042/serio4/input/input9
E: PRODUCT=11/2/7/12b1
E: NAME="SynPS/2 Synaptics TouchPad"
E: PHYS="isa0060/serio4/input0"
E: EV==b
E: KEY==6420 7000f 0 0 0 0
E: ABS==11000003
E: MODALIAS=input:b0011v0002p0007e12B1-e0,1,3,k100,101,102,103,110,111,112,145,14A,14D,14E,ra0,1,18,1C,mlsfw
E: SUBSYSTEM=input

Udev merely collects text attributes from sysfs, so it's expected
that all the attributes are the same as kernel says they are.

> udev/hal already use sizeof(long) to determine the length of a long
> word length, and it doesn't seem to happen everywhere. (I am running a
> 64 bit kernel/userspace and get correct results).

It works correctly with 32bit userspace and 32bit kernel too.

> I might have misunderstood you, but did you actually try to run a 64
> bit kernel under 32 bit userspace? That would explain the bug, since
> hal/udev were compiled with the assumption that sizeof(long) == 4,
> while the kernel prints those in groups of 8 bytes.

This is exactly what happens, to me and to the original bug reporter --
we both are running 32bit userspace and 64bit kernel.

Note that the difference between ioctl and sysfs is exactly in this
kind of issues: to be independent of word size... ;)

> So if we want to support mixed kernel/userspace word lenghts, we need
> to change the logic to do a dynamic word size detection based on
> uname().

Not uname please.  There should be a better way :)

For example, see the number of words shown in "key" attribute:
for 32bits it's two times of 64bits...

/mjt