Vojtech Pavlik wrote:
On Thu, Jul 07, 2005 at 05:20:59PM +0300, Anssi Hannula wrote:
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).
That sounds interesting. However - I don't know of many devices that'd
be PID compliant except for the MS SideWinder ForceFeedback Pro 2.
All the Logitechs, as far as I know don't implement full PID.
Unfortunately so :( Do you have any info on how close the FF
implementation of the common FF devices is to the PID standard?
I had a poor choice of words in the previous message; I have only little
code written, mainly I've been just thinking on a bunch of ideas on how
we could do these things better (in other words, I've taken a summer break).
What I have written, is the PID driver (not complete yet) and a simple
FF driver for Zeroplus based devices (VID 0x0c12, PID 0x0005 and 0x0008,
very cheap Playstation-pads with USB connector, I have two branded "XFX
Executioner Dual Impact" (BTW, their Windows driver is crap, doesn't
support multiple devices and hangs Control Panel windows continuosly)).
I could post a patch for the Zeroplus support, but with current FF
driver model, that would be 90% copy-paste of hid-tmff.c & hid-lgff.c.
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?
I don't think that the fact that when a process holds the device open
twice, the first close flushes the FF effects is that big a problem.
Ok.
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?
Probably both. The timing sensitive stuff in the kernel, all the rest in
an userspace library.
Hmm, that wouldn't leave much stuff into the userspace library (Effect
storage for devices without memory, converting effects with envelopes to
magnitude+time -sequences for devices without envelope support, etc).
Maybe we should implement everything in the kernel... I have to think
about it, maybe something big that should be implemented in userspace
comes to my mind.
--
Anssi Hannula
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