On Thu, 16 Feb 2006, Mukund JB. wrote: > Yes, I have a specific question regarding the control transfers in USB > 2.0 specifications. > Please refer to following paragraph in 5.5.3 Control Transfer Packet > Size Constraints:- > > An endpoint must always transmit data payloads with a data field less > than or equal to the endpoint's wMaxPacketSize (refer to Chapter 9). > When a control transfer involves more data than can fit in one data > payload of the currently established maximum size, all data payloads are > required to be maximum-sized except for the last data payload, which > will contain the remaining data. > > My quote: > wMaxPacketSize is 8 for low and 64 for high speed devices. > > After that see the Table 5-1. Low-speed Control Transfer Limits. > Even though there are a total of 43 bytes to be transferred, I observe > that data payload is less that 8 bytes some times which is against the > above rule in 5.5.3.
Where do you get that 43 from? The table has 4 rows. The first row illustrates what happens when 1 byte is to be transferred. The second row illustrates what happens when 2 bytes are to be transferred. The third row illustrates what happens when 4 bytes are to be transferred. And the fourth row illustrates what happens when 8 bytes are to be transferred. In each case there is only one data packet. Since there is only one, it is the last one. Hence it is free to carry fewer than 8 bytes. Alan Stern ------------------------------------------------------- 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
