Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33A86C282C4 for ; Tue, 12 Feb 2019 15:27:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D07720836 for ; Tue, 12 Feb 2019 15:27:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730514AbfBLP1O (ORCPT ); Tue, 12 Feb 2019 10:27:14 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:55932 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1728273AbfBLP1O (ORCPT ); Tue, 12 Feb 2019 10:27:14 -0500 Received: (qmail 1624 invoked by uid 2102); 12 Feb 2019 10:27:12 -0500 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 12 Feb 2019 10:27:12 -0500 Date: Tue, 12 Feb 2019 10:27:12 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Lorenzo Bianconi cc: Stanislaw Gruszka , Stefan Wahren , Felix Fietkau , Doug Anderson , Minas Harutyunyan , USB list , linux-wireless Subject: Re: [BUG] mt76x0u: Probing issues on Raspberry Pi 3 B+ In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Tue, 12 Feb 2019, Lorenzo Bianconi wrote: > Hi Alan, > > I actually used usb_sg_init()/usb_sg_wait() as reference to implement > mt76u {tx/rx} datapath, but I will double-check. > I guess we should even consider if there are other usb host drivers > that do not implement SG I/O and it is worth to support. > I am wondering if the right approach is to add SG to the controller > one by one or have legacy I/O in mt76 (not sure what is the 'best' > approach) > What do you think? If mt76u can use usb_sg_init/usb_sg_wait, that would be the simplest. It would allow you to remove a lot of code from the driver. And then adding SG support to the controller drivers one by one would be fine. However, if that isn't feasible then you have to keep legacy I/O in mt76u as long as any controller drivers don't support SG. Alan Stern