On Sun, 5 Nov 2006, Till Harbaum wrote: > Ok, i now basically got two different advises: > > - Use restricted control transfers > - Use interrupt transfers > > The latter has the disadvantage to not reliably work with 2.4 kernels > i have been told here. > > As i am not a usb guru i'd prefer an answer from you guys: What's > the nicer way to do this? INT transfers or restricted control transfers? > I don't need performance, the control transfers are just fine for me. > > It'd be nice if i could still provide a libusb based demo app for those > people who want to use my interface directly wirhout the kernels > i2c framwork. > > What's the way to go? > > I am really sorry to bother you, but it's imho nicer to have a clean > interface that the gurus here would consider "ok" than something > that has some flaws just because i didn't ask.
You should use whatever is most appropriate for your application. Interrupt endpoints have a specific purpose in USB: They are meant for data transfers that require a bounded latency. The host guarantees that the endpoint will get sufficient bandwidth to transfer a packet every N frames, where N is the number specified in the endpoint descriptor. With control endpoints the guarantee is a lot weaker. The host guarantees only that 10% of the total bandwidth will be available for all control transfers on the bus. On the other hand, usually a lot more bandwidth will be available and the control transfers will be able to take advantage of it, which is something interrupt transfers can't do -- they are allowed only their 1 packet every N frames. Don't worry too much about what Wolfgang said. I'm pretty sure that either choice can be made to work under Linux 2.4. You should make your decision based on which is most appropriate for your needs. And bear in mind that as time goes by, more and more of your users will be using 2.6 instead of 2.4. Alan Stern ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&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
