On Thu, Feb 09, 2006 at 09:32:41AM +0100, Martin Diehl wrote: > On Wed, 8 Feb 2006, Greg KH wrote: > > > > Driver needs to deal with several configurations with multiple interfaces > > > each. Custom-designed protocol. Both bulk and iso endpoints with latency > > > requirements. Not hard realtime, but response time is critical which > > > became tricky when sharing locks f.e. > > > > Response time to incomming packets (to turn around and send something > > else out?), or response time for something else (queuing, etc.)? > > Queueing was one issue. Another point f.e. is the device uses the USB > SOF-counter as its internal hardware clock. Certain requests to the device > need to deal with some timestamp operation (like saying "execute this > request at a particular frame-#"). For this to work the driver needs to > read the current SOF-counter and submit the urb such that the device will > execute it within about 5ms (in most cases - if we were missing this every > now and then, no problem). Would this be possible with usbfs - I mean for > iso-support the frame counter needs to be accessed anyway?
Yes, I think this should be possible with usbfs, all the necessary fields are exported to userspace. And we have reports of iso packets working at full bandwidth (usb 2.0 speeds) just fine through the interface, so I'm very hopeful it will work for you. > And some final word about "taking from Linux". Sure, using it for the > system is taking from it. As you know, personally I'm not abusing this as > an one-way-street. I've released drivers under GPL, contributed patches to > the kernel and tried to help other people - this was financed from my > private money, no sponsor or distributor paying me. Yes, I am very aware of your contributions in the past, and they are greatly appreciated. > Don't get me wrong, of course I do know many people have contributed > much more and I also know this wouldn't buy me the right to do things > violating the GPL. But that's not the point, I'm not asking for some > special admittance nor do I want to violate the GPL. I'm just > wondering about making a personal mistake when believing in the "give > something back" approach and tried to be fair. But anyway, this would > be my personal problem so let's just return to the technical issues. Ok, I'm sorry, that was a bit uncalled for on my part, and I apologize. It's just that closed source drivers cause lots of people lots of problems, myself especially, that over time, we get very grumpy about the whole situation... > But even if it became technically possible, the two other points remain: > Why investing the major effort of rewriting and validating an existing > working legitimate driver just because people decide to express their > intent that way, as you explained? And, what is the price of depending on > usbfs in the critical path? I agree, those are points that you need to decide for yourself. You need to look at your future product plans to determine this in the best manner. > cross-platform isn't an issue here. What I'm looking for - besides other > things of course - would be a platform where I can trust on rather stable > api on the longer timescale. Having to update the driver every few years > isn't a big deal - in contrast to driver rewrite just because people > express their intention. Taken this way I really appreciate your patch as > it makes clear the direction Linux is probably going in the future so > everybody can make up his mind. The user/kernel boundary api is the strongest that we currently have. I'd trust that the most. thanks, greg k-h ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=103432&bid=230486&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
