On Thu, Sep 22, 2005 at 10:23:13AM +0530, Savita H. Neelannava wrote: > Hi All, > > I have a Scanner device which has 3 Endpoints. wMaxPacketSize of all 3 > is 0x200. In the driver also i was allocating memory of 0x200 bytes > for each Endpoint. i have bulk-in Endpoint where i will get scanned > image data. Earlier i was recieving this data in chunks of 0x200 > bytes. But there was a problem like , driver was not fast enough to > recieve data as device scans image. So Device buffer was getting > overflow, paper got jam there. But what one of my friend has done is, > even though wMaxPacket Size is 0x200 bytes, he is allocating 0x1000 > bytes for recieving data and same size he is submitting while > submitting urb. how is this!!!!!!!!!!!
urbs can be bigger than the endpoint size. It's up to the usb host controller to split them up into the proper endpoint size. This allows us to get a much better throughput on the bus as you have proved :) > After this there no jam and everything working fine. can u get more > data from enpoint than specified in wMaxPacketSize? if yes what is the > purpose of wMaxPacketSize? wMaxPacketSize is the real size of the endpoint as per the USB specification. hope this helps, greg k-h ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
