On Wednesday 13 October 2004 11:11 am, Brian Murphy wrote: > OK. But I have a Lasat modem which is ~6 years old which puts all the > class specific descriptors at the end after the *normal* descriptors > and which has worked up to 2.6.7.
That's probably when the CDC descriptor parsing was added; the first iterations didn't check for descriptors in "strange" places. > Now that we are chatting ;-), I don't see that the CDC standard > specifies the necessity of a union descriptor, Section 3.1.1 of the spec says "a Union shall be made...", and elsewhere it says that there's always a control interface. That applies to all CDC devices. And 3.6.2 says specifically that ACM devices have one. > a CDC modem > should be perfectly capable of functioning without the > interrupt notification interface (just a control interface), I have > certainly made one which has a dummy interrupt interface to > ensure compatibility with the linux driver but which *never* sends > anything over it as none of the information I can signal with it > (according to the specification) is useful. Again, 3.6.2 is specific in this case: needs a notification endpoint in the control interface. (Notification endpoints are optional for CDC Ethernet though...) Though it seems that a fully conformant device can exist without needing to issue any of the notifications from table 5. (That's certainly what Al Borcher's CDC-ACM firmware does, usb/gadget/serial.c though not yet in Linus' tree.) > Is it then a good thing to rely on the existance > of a union descriptor to signal the validity of a CDC device? For devices that allegedly implement a class specification, there need to be limits on how much nonconformance any given driver will tolerate. I think that's fine. Oliver's maintaining that driver now, and you may want to ask him instead... :) - Dave > > /Brian > ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
