Vojtech Pavlik wrote:
On Fri, Apr 08, 2005 at 08:29:52PM +0300, Anssi Hannula wrote:
This patch adds Force Feedback interface to joydev. I felt this
necessary because games usually don't run as root while evdev usually
can't be read or written by anyone else. Patch is against 2.6.12-rc2. If
there is a reason this can't be applied or needs modifications, please
say it :)
Modern distros usually chown() the event devices to the user logged on
the console, so this shouldn't be a problem. Anyway, I'm not opposed to
adding the ioctl()s, but you should also add 64-bit compatible versions
of them.
Well, with Mandriva 10.2 that happens only with jsX.
But I think we should not apply (with or without 64-bit) the patch (not
yet, anyway), as I'm (slowly) working on restructuring the kernel FF
interface and developing a user space library (and writing a generic HID
PID FF-driver).
As a matter of fact, I have two (lengthy) questions:
1. What would be the best way to decide when to delete the effects of a
specific process from the device? Currently it is done when flush is
called. However, if one process holds multiple fd's to the interface
(for example input fd through some gaming-input library and FF fd with
the FF library), when any of these closes, all effects are deleted. Good
way to overcome this would be fd-specific effects instead of
process-specific, but I've got no idea how that would be done. One
possible way would be introducing a new device file solely for the FF
(so there would be no reason to hold multiple fd's to this file by the
same process), but would that be overkill?
2. Many simpler devices do not have any effect memory, for example there
is just one HID report that is used to apply an effect and stop it. They
could share very much of their timing code (they have effect memories
and timers implemented in software in the kernel). These would also need
software handling of envelopes, which is currently not implemented at
all (also some effects could possibly be software emulated). So, should
these be implemented by the kernel at all or should they implemented in
the userspace library?
--
Anssi Hannula
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