Messages in this thread | | | Date | Fri, 08 Jul 2005 19:13:45 +0300 | From | Anssi Hannula <> | Subject | Re: [PATCH] Add Force Feedback interface to joydev |
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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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