On Thu, 11 Nov 2004, Hou Xiang ZHU wrote: > hello, > A simple question related to linux usb concept here: > > I am reading the USB Spec2.0 , Mass Storage Spec. as well as linux usb > code. I am little confused by some concept concerning URB,USB requests > and CBW/CSW. > > In my understanding, each time host want to send request or data to usb > device, it has to use usb_submit_urb(), > > The USB request has standard device request and Class-specific request, > for standard request, it is used to get general USB device info. but > when it is going to use class-specific request? > > what is the relationship between CBW/CSW and Class-specific request? > > so a URB contains either USB standard request or class-specific request > or CBW? how about actual data(for example when writing a file to USB > stick)? > > Thanks, > Houxiang Zhu
Part of the trouble is that you have forgotten the distinction between control and bulk transfers. Standard device requests and class-specific requests are both control transfers, whereas CBW and CSW (and file data) use bulk transfers. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
