> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-owner@xxxxxxxxxxxxxxx] On Behalf Of sundeep subbaraya > Sent: Friday, December 12, 2014 9:13 PM > > Hi Felipe, > > In DWC3 driver, for three stage Control OUT transfer there is a check: > > else if (!IS_ALIGNED(req->request.length, dep->endpoint.maxpacket) > > && (dep->number == 0)) {. > } > > I understand that we check for alignment of sizes and if not we > prepare trb with maxpacket and enable interrupt on short packet. In > databook I could not find anything related to this, it talks only > about addresses should be aligned. In Control transfer programming > model there is no difference between Control OUT or IN transfer, if > three stage transfer - prepare trb with length wLength. Initially I > followed this and not able to receive data on EP0 OUT.:( .After adding > the above check it is working. Please help me to understand why we do > this? Hi Sundeep, Please see section 8.2.3.3 "Buffer Size Rules and Zero-Length Packets" in the databook: For OUT endpoints, the following rules apply: - The total size of a Buffer Descriptor must be a multiple of MaxPacketSize The wording may be a little confusing, it actually means that the size of the data buffer for OUT endpoints must be a multiple of MaxPacketSize. Section 8.2.5 states it more clearly: - An OUT transfer’s transfer size (Total TRB buffer allocation) must be a multiple of MaxPacketSize even if software is expecting a fixed non-multiple of MaxPacketSize transfer from the Host. This rule applies to all OUT endpoint types, including Control endpoints. -- Paul ��.n��������+%������w��{.n�����{���)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
