On 9 Aug 2002, Shane Bryan wrote: | On Fri, 2002-08-09 at 14:03, Dmitri wrote: | > | > Likely, the camera uses the same chipset as older cameras. But the driver | > does not know about this ProductID, and I already know that it won't parse | > bulk endpoints. I also know about yet another VendorID from Veo. | | Forgive my ignorance (for it is LARGE), but not being a driver | developer, or all that familiar with USB protocols, but what is a "bulk | endpoint". Any readme references would be fine, not looking for a full | explaination here.
There are 4 transfer types in USB: control, interrupt, isochronous, and bulk. USB interface endpoints talk only 1 transfer type (each), so for a device to have bulk, interrupt, control, and isochronous transfers, it must have at least 4 endpoints -- and only control type is bidirectional, the others are IN or OUT only, so even more may be needed for bulk IN, bulk OUT, isoc IN, isoc OUT, interrupt IN, interrupt OUT, etc. Interrupt and Isoc transfers have guaranteed delivery times & rates. Isoc does not guarantee data integrity. Bulk transfers use leftover time slots, so they have no guaranteed delivery time/rate, but do have guaranteed data integrity (accuracy, thru CRC). Or to quote the USB 2.0 spec, section 5.4: <quote> The USB defines four transfer types: * Control Transfers: Bursty, non-periodic, host software-initiated request/response communication, typically used for command/status operations. * Isochronous Transfers: Periodic, continuous communication between host and device, typically used for time-relevant information. This transfer type also preserves the concept of time encapsulated in the data. This does not imply, however, that the delivery needs of such data is always time-critical. * Interrupt Transfers: Low-frequency, bounded-latency communication. * Bulk Transfers: Non-periodic, large-packet bursty communication, typically used for data that can use any available bandwidth and can also be delayed until bandwidth is available. </quote> Even more detail is available in the USB spec. -- ~Randy ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
